~ DECOMPOSITION 0F AQUATIC PLANTS IN LAKES ‘ Dissertation for the Degree of Ph. D. MICHIGAN STATE UNIVERSITY GORDON LAMAR GODSHALK 1977 This is to certify that the thesis entitled DECOMPOSITION OF AQUATIC PLANTS IN LAKES presented by Gordon 3 Lamar Godsha 1k has been accepted towards fulfillment of the requirements for Ph . D. degree in Botany 20% Date April 29, 1977 ABSTRACT DECOMPOSITION OF AQUATIC PLANTS IN LAKES By Gordon Lamar Godshalk Decomposition is oxidation of carbon and other elements that have previously been biologically reduced and is the balance of primary production in ecosystems. The difference between the amounts of carbon reduced by photosynthesis and oxidized by decomposition is the true net production of the ecosystem. Past discussion of decomposition in lakes has generally been limited to the mineraliza- tion of dead plankton sinking through the epilimnion. The importance of the littoral zone to the productivity of small lakes has become evident, and decomposition of littoral vegetation is a major component of carbon metabolism as well. This study was carried out to systematically determine the effects of temperature and oxygen concentration, two environmental parameters crucial to lake metabolism in general, on decomposition of five species of aquatic vascular plants of three growth forms. Samples of dried plant material were decomposed in flasks in the laboratory under three different oxygen regimes, aerobic-to-anaerobic, strict anaerobic, and aerated, each at 10°C and 25°C. In addition, in situ decomposition of the same species was monitored using the litter bag technique under four conditions. Gordon Lamar Godshalk Particulate detrital plant material was analyzed after decomposition of up to 180 days for weight loss and content of ash, total carbon and nitrogen, nonstructural carbohydrate, hemicellulose, cellulose, and lignin. The ATP content and dehydrogenase activity of the microflora associated with this material was also determined. The dissolved matter in the flasks of the laboratory experiments was analyzed for pH, redox potential, total carbon and nitrogen content, and fractionated by membrane ultrafiltration into five molecular weight categories. Total dissolved organic carbon (DOC), UV absorb- ance, and fluorescence activity were determined for each fraction. Reducing conditions were established within 10 to 25 days during anaerobic decomposition at 10°C and within two days at 25°C. DOC concentrations increased throughout the decomposition period during anaerobic incubation at 10°C. DOC increased and then decreased in media of anaerobic experiments at 25°C. Only low DOC concentra- tions were found in aerated media at either temperature. Low molecular weight fractions were most rapidly metabolized under all conditions. UV absorbance and fluorescence data indicate that qual- itative changes in the DOC were occurring during decomposition. Weight loss functions, derived from the data, fit best when the functions were exponential with decay coefficients that also decreased exponentially through time, indicating that decay of macrophytic material was rapid initially and then slowed as resistant materials dominated the residual tissue. Decay rates were slightly greater in oxygenated than in anoxic conditions, but increased temperature caused significantly faster weight loss. Presence of Gordon Lamar Godshalk oxygen greatly promoted conversion of DOC to carbon dioxide. Weight loss of the various species was related to total initial fiber and nitrogen concentrations. The C:N ratios of particulate matter generally decreased under all conditions in all species, and in all species dissolved nitrogen was removed from the media during decomposition. Microbial activity associated with the detrital material generally attained maximal values early in decomposition and then decreased. The variety of conditions of temperature and oxygen that commonly occur in a temperate dimictic lake causes pulsed decomposi- tion of the annual production of littoral vegetation. Thus, the metabolism of carbon of aquatic macrophytes is displaced in time and space, and a stable continuous input of energy to the detrital dynamic structure of the lake is maintained. Eutrophication, promoting increased production of littoral zone vegetation, causes decomposi- tion processes in the lake to be overloaded, resulting in more extensive reducing conditions in the sediments and greater sedimenta- tion of particulate material. DECOMPOSITION 0F AQUATIC PLANTS IN LAKES By Gordon Lamar Godshalk A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY n. K. Kellogg Biological Station Department of Botany and Plant Pathology 1977 © Copyright by GORDON LAMAR GODSHALK 1977 ACKNOWLEDGEMENTS It is my pleasure to thank Dr. Robert Wetzel, Dr. Michael Klug, Dr. Patricia Werner, and Dr. Earl Werner for their services on my guidance committee. Dr. Wetzel generously provided the technical help of Jayashree Sonnad, Sharon Morrison, Janet Strally, David Duval, and many others whose willing assistance was invaluable. Dr. Klug and John Molongoski helped me with anaerobic techniques and cooperated with several aspects of this project not reported here. Steven Weiss provided patient assistance with all aspects of data analysis, inter- pretation, and presentation performed on the computer system at the Kellogg Biological Station. I benefited from discussions with my fellow students, particularly Wilson Cunningham, John Molongoski, Robert King, George Spengler, Kelton McKinley, and Amelia Ward, who were always eager to provide ideas and suggestions. I am grateful to members of the staff of the Kellogg Biological Station for their many valuable and usually unrecognized contributions to my efforts: Mary Shaw, Madelon Davidson, Arthur Weist, Mary Hughes, Charlotte Seeley, and Dolores Haire. I thank Dr. George Lauff for his efforts in providing facilities at KBS. Nancy Dyer, who suffered much of the tedium and shared in little of the satisfaction of this research, contributed in countless ways. ii I am indebted to Dr. Wetzel not only for his logistical support of this work, but also for his enthusiasm and encouragement. I appreciate the numerous contributions he has made to my education in aspects beyond research and the many opportunities that he has provided for me. Finally, I owe much to Dr. Gerald Moshiri, who first defined "detritus" for me and encouraged me to learn more. This research was supported by funds granted to Dr. Wetzel from the U.S. Energy Research and Development Agency (EY-76—S-02-l599, COO-1599-121), and the National Science Foundation (BMS-75-20322 and 0EC-74-24356-A01). My early efforts were made possible by a National Science Foundation grant to Dr. Lauff et al. for Coherent Areas Studies (GB-403ll). TABLE OF CONTENTS Page LIST OF TABLES ......................... vi LIST OF FIGURES . . . . . . . . ..... . .......... vii LIST OF ABBREVIATIONS ................ . ..... 1x INTRODUCTION . . . . . . ..... . .............. l Production, Decomposition, and Net Ecosystem Production. . 1 Importance of Decomposition in Lakes . . . . . . . . . . . 4 Past Studies . . . ..... . . . . . . ......... 6 Objectives . . . . . . . . . . . . . . . . . . . . . . . . 8 METHODS. . ........................... ll Laboratory Experiments . . . . . . . . . . . . . . . . ll Sample Preparation and Incubation . . . . ....... ll Sampling Procedure ...... . . . . ..... . . . . l4 Particulate Matter Analyses ....... . . ..... Zl In Situ StUdieSo O O O O O C O O O O O O O O O O O O O O O 24 RESULTS AND DISCUSSION ..................... 26 Redox Potential and pH . . . . . . . . . . . . . . . . . . 26 Dissolved Organic Matter . . . . . . . . . . . . . . . . . 32 Dissolved Organic Carbon. . . . . . . . . . . . . . . . 32 Ultraviolet Absorbance, Fluorescence. . . . . ..... 35 Resistant Compounds . . . . . . . . . . . . . . . . . . 47 Particulate Organic Matter . . . . . . . . . . . . . . . . 49 Weight Loss . . . . . . . . . . . . . . . . . . . . . . 49 Carbohydrates, Fiber Components ............ 62 Microbial Metabolism . . . . . . . . . . . . . . . . . . . 72 ATP Content . . . . . . . . . . . . . . . . . . . . . . 72 ETS Activity. . . . . . . . . . ....... . . . . . 75 Nitrogen and Decomposition ..... . . . . . . . . . . . 77 Particulate Nitrogen. . . ...... . . . . . . . . . 78 Dissolved Nitrogen. . . . . . . . . . . . . . . . . . . 80 Discussion. . . . . . ........ . ........ 81 The Importance of Decomposition Rates. . . . . . . . . . . CONCLUSIONS. . . . . ..... . ................ Fates of Decomposing Organic Matter ............ Decomposition in Lakes . . . . . . . . . . . . . ..... Temperature and Oxygen in Lakes . . .......... Annual Cycle of Decomposition . . . . . . . . . . . . . Effects of the Decomposition Cycle. . ......... Response of Decomposition to Eutrophication. . . . . . . . SUMMARY. ..... . ...................... LITERATURE CITED ........................ APPENDIX Graphs of Parameters of Decomposition of Macrophytes . . . Page 128 LIST OF TABLES Table Page I 2 Components of synthetic lake water (Wetzel Medium 5) used in laboratory decomposition experiments. . ..... l3 Decay rate constants of exponential functions of best fit to weight loss data of aquatic macrophytes under differing experimental conditions . . . . . . . . . . . . 52 Parameters of exponential functions of best fit to macrophyte weight loss data where the decay coeffi- cient decreases exponentially with time. a_is the initial rate of weight loss which declines expon- entially through time at a rate of 9, (From Godshalk and Wetzel, l977b.) ................... 57 Initial content of fiber components (as percent of ash- free dry weight) of senescent macrophytes. (From Godshalk and Wetzel, l977b.). . . . . . . . . . . . . . . 69 Initial nitrogen and carbon content (as percent of total dry weight) and the C:N ratio of senescent macrophytes. (From Godshalk and Wetzel, l977b.). . . . . . . . . . . . 88 'Summary of conceptual models used to explain rates of natural decomposition of biological tissues, modified slightly from original forms for comparative purposes . . 92 vi LIST OF FIGURES Figure Page I Results of fractionation of dissolved organic matter produced after 43 days of aerobic-to-anaerobic decomposition of Najas flexilis at l5°C. Fractions are filtrates of severaTifilters of decreasing nominal pore size: A, 0.4 pm, Reeve-Angel 984H glass fiber; B, 0.4 pm, Millipore HA membrane; C, 0.2 um, Millipore GS membrane. The following are Diaflo type (Amicon Corp.) membrane ultrafilters: D, 300,000 MW, XM-300; E, l00,000 MW, XM-lOOA; F, 50,000 MW, XM-50; G, 30,000 MW, PM-30; H, l0,000-20,000 MW, UM-20E; J, 10,000 MW, PM-lO; K, 10,000 MW, UM-lO; L, l,000 MW, UM-2; M, 500 MW, UM-OS. . . . . . . . . . . . . . . . . . l6 2 DOC and UV absorbance of various molecular weight fractions of 00M from flasks containing Scir us subterminalis during aerobic decomposition at 5°C . . . 39 3 DOC and fluorescence activity of various molecular weight fractions of DOM from flasks containing Nuphar variegatum during aerobic-to-anaerobic decomposition at 25°C . . . . 4l 4 UV absorbance and fluorescence activity of various molecular weight fractions of DOM from flasks containing Scirpus subterminalis during aerobic decomposition at ZSUC. O O O I O O O O O O O O O O O O O O O O O O O O O O 43 5 Graphs of functions (solid lines) of weight remaining over time fit to actual data (triangles) for Na'as flexilis during aerobic-to-anaerobic decomp051t1on at 25°C: (a) simple exponential function, k = 0.028, correlation coefficient (observed vs. predicted weight remaining) r = 0.96; (b) exponential function where k_is an exponential function as well, a = 0.063, b = 0.049, r = 0.99. See text for explanation of parameters. . . . . . . . . . . . . . . . . . . . . . . . 53 6 Derivation of exponential function fitted to weight loss data where the decay coefficient is itself an exponential function of time. W = percent of ash-free dry weight remaining; t = days of decomposition; a, b = constants vii Figure Page obtained by least squares computer fit of function to actual data . . . . . . . . . . . . . . . . . . . . . 56 7 Total nonstructural carbohydrates (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) components as percent of recovered AFDW, of Scirpus acutus during in situ decomposition under four conditionszTTa) Lawrence Lake littoral zone, summer; (b) Lawrence Lake littoral zone, winter; (c) Lawrence Lake pelagial zone, winter; (d) Wintergreen Lake littoral zone, winter. See text for explanation. . . . . . . . . . . . 66 8 Relative importance, with respect to rates and total accumulation, of the four possible fates of macrophytic tissue observed during decomposition under various conditions of temperature and oxygen concentration. See text for further explanation. (From Godshalk and Wetzel, l977a.) . . . . . . . . . . . 96 9 Distribution of temperature and oxygen at depths of 3 and l2 m in the pelagial zone of Lawrence Lake, l975. Hatching on upper abcissa denotes period of ice cover; hatching on center abcissa indicates periods of isothermal conditions during spring and fall turnover. See text for further explanation . . . . 99 10 General diagrammatic representation of seasonal con- ditions of carbon metabolism of particulate and dissolved organic carbon of macrophytic origin in a typical temperate, dimictic lake of intermediate productivity. See text for explanation. (From Godshalk and Wetzel, l977a.) . . . . . . . . . . . . . . 102 viii LIST OF ABBREVIATIONS AFDW ATP C:N DOC DOM ETS LDOM MW NEP POM RDOM TNC ix Ash-free dry weight Adenosine triphosphate Degrees Celsius Carbonznitrogen ratio Dissolved organic carbon Dissolved organic matter Redox potential, compared to standard hydrogen half-cell Electron transport system Labile dissolved organic matter Molecular weight Net ecosystem production Particulate organic matter Resistant dissolved organic matter Total nonstructural carbo- hydrates INTRODUCTION Production, Decom osition, and Net Ecosystem rEHUCtion In its strictest sense, the term "decomposition" as used in this study refers to the conversion of the products of phytosynthesis and subsequent plant syntheses back into the form of the reactants of those syntheses. Carbon and most other nutrient elements, are oxidized to inorganic or mineral form by means of the decomposition or mineralization process. Decomposition includes less complete transformations of organic matter as well. The loss in weight of decaying plant tissue represents decomposition. By the laws of thermodynamics the tissue is not "disappearing“ but is being converted into a less obvious form, either gaseous or dissolved. The conversion of particulate organic matter (POM) to dissolved form is a step in the decomposition process, and dissolved detrital carbon is a resource of aquatic systems whose biotic importance is often underestimated (cf. Wetzel et al. l972). The oxidation of dissolved organic matter (DOM) by microbes is decomposition even if part of the dissolved carbon used as substrate is incorporated into their biomass. Primary production is the conversion of kinetic energy and inorganic carbon to potential energy in the form of reduced carbon. Decomposers use this potential energy, and in so doing convert the carbon and nutrient elements into more oxidized states. The conversion T of plant to animal biomass is secondary production and is really a form of decomposition since there is a net dissipation of carbon and energy in the process; the existence of a new form of tissue only delays the utlimate mineralization of the elements present. Thus, autotrophs function to bring reduced carbon into the ecosystem, while the heterotrophs exploit that source of carbon and eventually cause its removal from the ecosystem. The balance of the two processes, production and decomposition, is the net production of the ecosystem. Net ecosystem production (NEP) has been defined by Woodwell and Whittaker (1968, Woodwell et a1. 1973) as NEP = Gross Production - Respiration where Respiration includes that of both autotrophs and heterotrophs. NEP represents the mass of organic material produced by the system in a given period of time. Wetzel (1975:618) discusses the NEP concept as it pertains specifically to lakes. When this equation is used to determine the NEP of a particular system on a short term basis no correction is made for the fact that the Gross Production term includes much living biomass that has not yet had the opportunity to be decomposed, and the resultant value of NEP is a measure of living biomass plus detritus. If totally efficient and instantaneous decomposition were occurring in the system there would be no detritus, i.e. all non-living tissue would be respired, and NEP, as usually determined would be represented by only living biomass. Consideration of this amount as true NEP over long time periods is erroneous because eventually all currently living biomass will be dead and become available to the heterotrophs. For this reason, calculations of NEP should provide for decomposition (i.e. Respiration) to "catch up" to Gross Production, so that no substrates unavailable for decomposition exist. The result of the calculation then is an estimate of the amount of carbon fixed in the system but not lost by respiration. In ecosystems, detrital NEP theoretically exists as permanent detritus, photosynthate that will never be utilized as heterotrophic substrate. Practically speaking, in no ecosystem will there not exist a lag time between production and decomposition; indeed, that is the life span of biological tissue. Nor is there permanent detritus, as the residence times of even the most resistant compounds will be less than infinity. The point being made is that estimates of true ecosystem production should not be biased by amounts of living tissue, but instead should accurately represent the difference between production and decomposition over long periods of time when the rate of each of these processes is stable. Variations in conditions which cause either rate to change will cause the estimate to be in error until a new balance is stabilized. True net ecosystem production is the amount of organic matter that is not later decomposed over periods less than geological time (cf. Ohle, 1956; Batzli, 1974). For example, even though the productivity of the plant com- munity in a bog is considered low relative to other plant communities, decomposition rates in bogs are even lower, and a bog is in fact a productive ecosystem (Dickinson and Maggs, 1974). Numerous studies have determined the productivity of several different ecosystems, and this abundance of data has led to ranking and other comparisons of "ecosystem productivity." Usually these estimates are not of true ecosystem productivity and are more equivalent to agriculturalists' yield, that amount of biomass that has not yet decomposed and which can be harvested. The emphasis that comparative short term pro- ductivity studies have received has been at the expense of a thorough understanding of the net productivity of ecosystems. Importance of Decomposition in Lakes Decomposition of organic matter that is ultimately derived from photosynthetic fixation of carbon dioxide is the process by which a lake functions as an ecosystem. Continuing to consider the metab- olism of animals as a form of decomposition, it is apparent that the majority of the transformations of biomass and energy involve heterotrophic relationships among the various components. This is especially true of aquatic ecosystems where the lake or stream is literally the focal point of.much of the energetic activities which occur in the drainage area. In a lake with little input of organic matter from outside the water body itself, decomposition will almost equal production, the difference being permanently sedimented and exported. But in a basin where there is much allochthonous organic input to the lake, the flux of carbon through degradative pathways can exceed that in the form of autochthonous production and thus decomposition processes may easily be responsible for well over half of the total carbon metabolism of the system. Stream ecologists have recognized the dominant heterotrophic nature of small running waters and are presently making progress toward understanding these ecosystems (e.g. Cummins, 1974; Hynes, 1975). Lake limnologists, on the other hand, have been slow to investigate decomposition and relatively little is known of the ecosystem-level effects of heter- otrophic metabolism in lakes, especially when compared to the abun- dance of data that exists on production of phytoplankton. In spite of the paucity of experimental studies on lake decomposition, several ecologists have recognized and described what is coming to be known as the "detrital dynamic structure" of aquatic systems (e.g. 0dum and de la Cruz, 1963; Wetzel et al., 1972; Pomeroy, 1974; Wetzel, 1975:606; see also Melchiorri-Santolini and Hopton, l972). Saunders (1976) points out that decomposition is the mechanism whereby a system can function when or where no light exists to stim- ulate photosynthesis. In lakes, in the north temperate zone especially, most primary production occurs during a relatively short growing season when waters are warm and light intensities high. For the remainder of the year, system metabolism depends on displacement of summer production in both space and time. Water movements trans- port potential energy in the form of plant tissue from the littoral and trophogenic pelagial zone to the tropholytic zone and benthic sediments. Often there is a significant transport of detrital carbon out of the lake to some other system (e.g. Wetzel and 0tsuki, 1974). Decomposition, as will be explained in this work, also occurs over extended periods of time, and one role of detrital carbon is as a store of potential energy which is utilized at some later time, often long after its creation. Past Studies Some studies have been done on the in situ decomposition of phytoplankton and detritus from plankton, and in the laboratory on aspects assumed or known to affect decomposition in nature. Kleerekoper (1953) found that detritus derived from plankton under- goes most decay while it is sinking in the epilimnion. The composi- tion of sinking detritus was almost the same by the time it passed through the metalimnion as the organic matter of the bottom sediments. Most nitrogen of the sinking detritus was released in the epilimnion. but phosphorus and silica were not as readily released and accumulated in the sediments. Similar results were described by Kuznetsov (1975: 208). Saunders (1972) followed the decomposition of artificially- prepared radioactively-labelled detritus in situ, and more recently phytoplankton decomposition was investigated in situ by Jones (1976). Several laboratory studies have centered on the mechanisms of decay and resistance to decay of algae (Foree and McCarty, 1970; 0tsuki and Hanya, 1972a, l972b; Mills and Alexander, 1974; Pierre et al., 1974; Gunnison and Alexander, 1975a, l975b; Verma and Martin, 1976). Pelagial decomposition predominates heterotrophic metabolism in large lakes and the observations described above are often taken to be the general case of lake decomposition. There are many times more small lakes (e.g.< 5 - 10 hectares in surface area) on the surface of the earth than there are large lakes. In small lakes, where the extent of shoreline and shallow water in relation to total lake volume is much increased, the plants of the littoral zone assume a greater part in the metabolism of the entire lake ecosystem (Wetzel and Allen, 1972; Wetzel, 1975:355; Mason and Bryant, 1975; Howard- Williams and Lenton, 1975; Gaudet, 1976). Studies on decomposition of macrophytes from the littoral zones of freshwater lakes are few and highly diverse in methodology, plant species and lake types studied, and interpretation. Ulehlova (1970, 1971) studied the zona- tion of aquatic macrophytes, some aspects of their decomposition, and effects on the sediments of three lakes in the Netherlands. Pieczyfiska (1972) examined aspects of both production and decomposi- tion of macrophytes of the eulittoral zone (above mean water level) in several lakes in Poland. The leaching of mineral nutrients from Phragmites was examined in detail by Planter (1970). Isolation and characterization of the microflora associated with decaying freshwater macrophytes have received considerable attention (e.g. Botan et al., 1960; Aliverdieva-Gamidova, 1969; Dickinson et al., 1974; Mason, 1976; Wheatley et al., 1976). The successive colonization of decaying Phragmites particles by various microbes has been documented by Olah (l972). Virtually all other studies of decomposing macrophytes are referred to during the discussion of various aspects of the present study. More investigations have dealt with salt water plants and their decomposition (e.g. 0dum and de la Cruz, 1967; Fenchel, 1970; Gosselink and Kirby, 1974; Harrison and Mann, l975a, l975b; de la Cruz, 1975). Schultz and Quinn (1973) looked in particular at the fatty acid components of Spartina alterniflora detritus; Gallagher et a1. (1976) and Fallon and Pfaender (1976) reported on the micro- bial metabolism of leachate from this salt water marsh plant. Much of the most informative investigation of the mechanisms and controlling factors of aquatic and marine decomposition processes was done almost half a century ago by Waksman and co-workers (e.g. Waksman and Stevens, 1928; Waksman et al., 1933; Waksman and Carey, 1935a, 1935b; Waksman and Renn, 1936). These works, in addition to Waksman's classic studies of terrestrial decay, provide much data useful in interpretation of modern experimental approaches and deserve greater attention by contemporary students of decomposition. Objectives No systematic studies of decomposition processes in lentic ecosystems have previously been performed in order to examine the biological and environmental controls over the dynamics of such processes. The primary goal of this research was to investigate the effects of plant species (i.e. species-specific structural character- istics), temperature, and oxygen on the transformations of various forms of carbon derived from senescent macrophyte tissue. Special attention was paid to the rates and products of decomposition, and to influences of particular components of the detrital material on overall decay of the whole tissue. Carbon, in various molecular forms, was selected to be mon- itored during decomposition because it is the basic atomic constituent of all biotic tissue. Other elements of great biological importance (i.e. hydrogen, oxygen, nitrogen, phosphorus, sulfur) participate in physiological reactions in various chemical combinations with carbon. Because of the close physiological connection between carbon and the other elements, knowledge of the fluxes of carbon at the same time provide some information on the transformations of the other elements as well. Much attention has been given to the elemental composition of living and decaying aquatic angiosperms (e.g. Gerloff and Krombholz, 1966; Allenby, 1968; Boyd, 1970b; Adams et al., 1973). Since the chemical composition of vascular aquatic plants is so variable depend- ing on species, environmental, and seasonal factors, care must be taken in interpreting decomposition data based on elemental contents of plants or their derivatives (Boyd and Hess, 1970; Boyd, 1970a). 0n the basis of the growth forms of various aquatic macro- phytes and their respective needs for rigid supportive tissue it was hypothesized that there would be significant differences in the decomposition of different species. Emergent plants, having at least their upper portions aerial and without water support were expected to be the most lignified and therefore slowest to decompose. Lignin gives plants rigidity and strength and is also important in water and nutrient transport in xylem (Wardrop, 1971). Submersed plants, being almost entirely supported by water and generally flaccid in structure were hypothesized to be relatively rapidly decompoééd. Floating- 1eaved plants were expected to exhibit intermediate rates of decay. Five species were selected for study: the emergent bulrush Scirpus acutus, the floating-leaved yellow water lily Nuphar variegatum, and the submersed water milfoil Myriophyllum hetergphyllum and bushy TO pondweed Najas flexilis, and the only submersed species of the genus of emergent bulrushes Scirpus subterminalis. Environmental conditions selected for study in the laboratory experiments were temperature and oxygen concentration. These param- eters are well recognized influences of biological processes in general, and are critical in the metabolism of lakes in particular. The lower temperature of 10°C approximates the highest temperature usually attained by pelagial sediments, and the high temperature of 25°C is approximately the highest temperature of surface and littoral waters during the summer in a north-temperate dimictic lake. Oxygen conditions in the lab experiments represent three natural situations: (1) aerobic-to-anaerobic conditions simulating the situation in a lake when a plant growing in oxygen-containing waters dies and collapses to an anaerobic sediment-water interface, (2) anaerobic, as when a plant is growing in waters that become anaerobic before the plant senesces and begins to decompose, and (3) aerobic, as in a wave-swept littoral area of continually oxygen- rich water. METHODS LaboratoryiExperiments Sample Preparation and Incubation Several kilograms of tissue of each of the five species of aquatic macrophytes studied were collected in the autumn, the end of the growing season for most of the species. At the time of collec- tion four of the species were beginning to senesce, but they were not yet dead and had undergone no microbial decomposition. Scirpus subterminalis, however, grows year-round in Lawrence Lake (Barry County, Michigan) where it was collected and so the plant tissue of this species obtained was largely in healthy condition (Rich et al., 1971). Najas flexilis and Myriophyllum heterophyllum were collected by grappling hook from the littoral zone on the west side of Gull Lake (Kalamazoo and Barry Counties, Michigan). Najas was also col- lected from Pine Lake (Barry County, Michigan). Nuphar variegatum and Scirpus acutus were gathered from Lawrence Lake. No attempt was made to separate out the small amount of root tissue of the submersed plants, but only the above-sediment portions of the floating-leaved and emergent plants were collected and used. Tissue of all species was washed free of sediments, air dried, and stored in large plastic bags with silica gel desiccant sachets until used. 11 12 For each experiment, 14 samples of each species were prepared. Approximately 3.5 g of plant tissue were lyophilized, weighed exactly, and put into a 1000 ml Erlenmeyer flask. One-thousand ml of freshly prepared synthetic lake water (Wetzel Medium 5, See Table l) were added, followed by a 20 m1 inoculum of sediments obtained from the littoral zone of Lawrence Lake. All media and plant tissues used in the strict anaerobic experiments were deoxygenated for 60 hours in an anaerobic glove box with an atmosphere of 85 N2:10 H2:5 CO2 (by volume). The deoxy- genated plant tissue and medium were combined in the flasks, the inoculum added, and the flasks tightly stoppered in this atmosphere as well. This treatment was sufficient to insure initial reducing conditions (Eh <100 mV). The high content of carbon dioxide in the glove box atmosphere causedaislight drop in the pH of the bicarbonate- buffered medium, but in no experiments was the initial pH different from that of the littoral zone by more than 0.5 pH unit. Experiments were performed at the appropriate time of year so that the temperature of the littoral zone sediments at the time of collection of the inoculum was as close as possible to the incubation temperature. Sediments to serve as inocula in the anaerobic experi- ments were obtained using techniques minimizing exposure to oxygen and were kept under a non-oxygenated atmosphere until added to the flasks. Flasks of aerobic-to-anaerobic and strict anaerobic experi- ments were sealed tightly with silicon rubber stoppers. Aerobic flasks were stoppered with foam plugs through which Tygon tubing was Table 1. 13 Components of synthetic lake water (Wetzel Medium 5) used in laboratory decomposition experiments. Compound* mg/liter NaHCO3 500. KZHPO4 200. KNO3 100. NH4Cl 100. MgSO4-7H20 100. CaCl2 54. KCl 30. Na25i03-9H20 23. FeCl3 1.38 ZnCl2 0.48 H3803 0.40 NazMoO4~2H20 0.254 CuCl2 0.0085 CoClZ-GHZO 0.0081 MnC12-4H20 0.0055 * All compounds analytical reagent grade, dissolved in distilled-deionized water; pH of medium ~8.2. 14 installed to provide aeration. The aerobic flasks were bubbled sufficiently to maintain oxygenated conditions (Eh >100 mV) with synthetic air (Linde Div., Union Carbide Corp.) premoistened by bubbling through distilled water. All flasks were incubated in the dark in environmental chambers at 10°C or 25°C; temperature was maintained constant to within 1°C. Sampling Procedure Two flasks of each plant species were sacrificed after about 2, 4, 10, 24, 48, 90 and 180 days of decomposition during each experiment. This sampling schedule was selected to provide more information on the initial stages of decomposition when changes, particularly in the dissolved detritus, were occurring more rapidly. A platinum electrode was put into the flask and the redox potential measured against that of a calomel reference electrode filled with saturated potassium chloride. The reference electrode was joined to the sample by a conductivity bridge of 3.5 M potassium chloride in 1.5 percent (w/v) purified agar in Tygon tubing. The surface of the platinum electrode was burnished with crocus cloth and rinsed with glass distilled water between all determinations; measure- ment of cell potential was made on a Coleman Model 38A expanded scale pH meter on millivolt mode after an equilibration period of ten minutes. The reference half-cell potential was determined on each sampling day by calibration against ZoBell solution (1/300 M potassium ferrocyanide and 1/300 M potassium ferricyanide in 0.1 M potassium chloride; Whitfield, 1971:102) and the Eh at sample temperature calculated. A small sample of medium was poured from the flask into a 15 disposable beaker, sealed from atmospheric oxidation, and allowed to attain room temperature. The pH of this sample was measured with a Corning combination pH electrode after a sample-electrode equil- ibration time of ten minutes on a Beckman Expandomatic pH meter standardized daily to temperature-corrected pH of certified buffer solution (Fisher Scientific Co.). Medium was poured out of the flask without disruption of the inoculum sediments at the bottom and filtered sequentially through 160 um nylon mesh (Nytex), precombusted (525°C, three hours) glass fiber filters (Reeve-Angel 984H, pore size 0.4 pm), and finally 0.2 pm pore size membrane filters (Millipore Corp., type GS). Some of the filtrate was lyophilized for later analysis of the residue; the remainder was subjected to membrane ultrafiltration for fraction- ation by molecular weight of the DOM. Diaflo type membrane filters (Amicon Corp.) with nominal molecular weight cutoffs at 30,000 (PM-30), 10,000 (PM-10), 1,000 (UM-2), and 500 (UM-05) were selected because these filters provided the most distinct molecular weight fractions in preliminary tests on the dissolved products of decomposing macrophytes (see Figure 1). The filters were prewashed to prevent contamination of the samples by the filter preservative (Wilander, 1972), and the first portion of the filtrate obtained was discarded. The media were put through the PM-30 and PM-lO filters in sequence, some of the filtrate being reserved from each fraction for analysis; most of the PM-lO filtrate was divided into two parts for filtration through the UM-2 and UM-05 membranes. 16 00120 32 oom N120 z: 000.— opuza 22 000.0— 0—120 3: 000.0? momuzn 32 000.0N1000.0P 001:; 32 000.00 00-:x 32 000.00 <00F12x 3: 000.00P oomuzx zz 000.00m z 4 x 0 I 0 m m 0 ”memu__%mcp_: memenEmE a.aeou couwsmmm E: e.0 0 0 < ”mNWm mgoa Pmcweo: mcwmmmgumu Lo mgwapww Fmgm>mm we mmuegg_wm men mcowpumcm .uomp pm mPPmePC mmmoz Co cowpwwoaeoumu uwnogmmcmuop10Pnogmm +0 mace me Lmumm uwuavoca coupes uwcmmgo um>Pommvu Co :owumcowpumem Lo mppzmmm .— mczmwm (mg/l) I DOC ,II 1111 8 ’ A 2 9 9 x X II I 5 8 IIII l _J a a o E II III In E3 8 ’ a: [D g <1 , II III II II II II a 5 ’ ’ VA "1" In III III II II II II [I II III II II II III 111 V//////// 0 III II II II II II III W 1 LL II II III III III III III 7////// A Lu III III 11111! 111 III III ”zvy' I IIII 111 111111 III III 111 V////// . , II II II H II II II III ézzy' [ID II II III III III II II II III I 7////// A < W T 1 fl 0 30()~ ZOO-e 100— FRACHONS Figure l 18 The unfractionated medium (i.e. 0.2 pm filtrate) and each of the four molecular weight fractions were analyzed for total DOC, UV absorbance, and fluorescence. DOC was determined by a slight modification of the persulfate oxidation method of Menzel and Vaccaro (1964) and measured by infra- red carbon dioxide analysis on a Beckman 215A infrared gas analyzer. Samples were variously diluted to provide concentrations of DOC in the analyzed samples of l to 10 mg/l in order to insure complete oxidation of the samples. Absorbance of ultraviolet light (250 nm) was measured using a Hitachi Perkin-Elmer Model 139 UV-VIS spectrophotometer, reading the samples at room temperature in quartz cells of 0.5 cm path length against a blank of glass distilled water; corrections were made for dilution when necessary due to high absorb- ance. Fluorescence was determined on a Turner Model 110 Fluorometer equipped with an ultraviolet lamp and primary filter providing excitation at 365 nm and combined secondary filters to measure emission at 545 nm. Readings were made against a blank of glass. distilled water, normalized to scale 3X, and reported as fluorometer units. Fluorescent emission was also measured at 460 nm but is not reported here because of the problem in interpretation resulting from excessive quenching of the samples at this wavelength and the frequent need for dilution of the highly active samples (Guilbault, 1973:147). Fluorescence determinations were made at room temperature, and no correction for or adjustment of sample pH was made. As much particulate material as possible was recovered from each flask; the amount of inorganic material originating from the 19 sediment inoculum contaminating the tissue was minimized. Recovered tissue was lyophilized and weighed, and then ground in a micro-Wiley mill (Arthur Thomas Co.) to pass through a 1-mm mesh. Samples of this material were assayed later for content of ash, carbon, nitrogen, total nonstructural carbohydrates, and fiber constituents. The tissue in the second flask of each species sacrificed each sampling day was used to determine microbial activity associated with the decomposing plant matter by two methods, ATP content and electron transport system (ETS) activity. The latter is essentially an indirect measurement of the activity of dehydrogenase enzymes (Curl and Sandberg, 1961). Plant tissue was taken from the flask with long forceps and gently blotted to remove excess water. A subsample of about 2.6 g (wet weight) was extracted for ATP, two subsamples of about 0.1 g each (wet weight) were used to determine ETS activity, and the remainder was weighed, lyophilized, and weighed again to correct the analyzed subsamples from wet weight to dry weight. All of the tissue from the second flask not used in the microbial activity assays was lyophilized and combined with the tissue from the other flask of the pair during the grinding procedure. ATP was extracted by the method used by Suberkropp and Klug (1976). Fifteen m1 of 0.6 N sulfuric acid were added to the tissue sample in a 50 m1 polycarbonate centrifuge tube and the mixture homogenized for two minutes in an ice bath by a Virtis 23 homogenizer; total extraction time was 30 minutes. The supernatant was vacuum filtered (Reeve-Angel 984H glass fiber filter), diluted with an equal 20 volume of 0.05 M HEPES (N-2-hydroxyethyl—piperazine-N]-2-ethane sulfonic acid) - magnesium sulfate buffer (pH 7.5), and the final pH adjusted with sodium hydroxide to 7.2. The extracts were,frozen at -60°C until assayed. The efficiency of extraction was not determined but was assumed to be constant, as in the reference study, allowing relative comparisons of samples within this study. The frozen samples were thawed, centrifuged, and kept on ice when assayed. The amount of ATP extracted was determined by measur- ing the light emitted when the sample reacted with a luciferin— luciferase enzyme complex (Sigma Chemical Co.) in an Aminco Chem Glow photometer with output to a 651-208 integrator and compared to an ATP (Sigma Chemical Co.) standard curve. Corrections were made for interfering substances which caused a quenching of the light emitted by repeating the reaction with sample material to which was added an internal standard of ATP. The analysis of ETS activity was similar to the method des- cribed by Zimmerman (1975). All the moist tissue samples for assay of ETS activity, except those which were from aerated flasks, were handled and incubated in the reduced atmosphere of the glove box so that the transport system would not be poisoned by oxygen. The two 0.1 9 samples of plant tissue from the second flask were put into 50 m1 polypropylene centrifuge tubes and 2 m1 of phosphate buffer (pH 7.7) added. To one tube (the treatment sample) was added 1.00 ml of solution containing 1 g INT (2-P-iodophenyl)-(3-P-nitropheny1)-5- phenyl tetrazolium chloride (Schwarz-Mann) in glass distilled water to make 500 m1, and to the other tube was added 1 m1 of glass distilled 21 water; the second tube served as a correction for colorimetric interferences caused by extraction of pigments from the plant material. All tubes were tightly capped and incubated 20 minutes at the same temperature from which the samples were taken. The reaction was stopped by addition of a 2:3 solvent mixture of tetrachloroethylene: acetone. Reduction of INT by microbial electron transport systems during incubation produced formazan which is insoluble in water but soluble in this solvent. Formazan was extracted overnight in a freezer (-20°C), after which the biphasic mixture was vacuum filtered (Reeve Angel 984H glass fiber filters), and the residue quantitatively washed with solvent until no more color was removed. Intensity of formazan color was measured spectrophotometrically at 490 nm, corrected for solvent volume and absorbance of the blank to which no INT was added, and reported in relative absorbance units per g tissue ash- free dry weight. Particulate Matter Analyses A 50 - 100 mg portion of the ground plant tissue was combusted in a muffle oven at 550°C for three hours to determine the mineral ash in each sample. The data of subsequent assays (except carbon- nitrogen analyses) were then corrected for ash content, and these data are reported on an ash-free dry weight basis. The total carbon and nitrogen as percent of total weight of the recovered plant material, and in the residue of the lyophilized unfractionated media, were determined on an automated analyzer (Carlo Erba Elemental Analyzer Model 1104). 22 Total nonstructural carbohydrates (sugars, starches, etc.) were determined enzymatically by the method of Smith (1969). Approxi- mately 100 mg of ground plant tissue was boiled in glass distilled water for two minutes to gelatinize the starches, then cooled to room temperature. Acetate buffer (pH 4.45) and 0.5 percent (w/v) takadiastase enzyme solution (Clarase 900, Miles Laboratories, Inc.) were added, and the mixture incubated at 38°C for 48 hours. This enzyme preparation hydrolyzes disaccharides and starches to monomers and has little effect on structural carbohydrates. The dissolved carbohydrates were filtered off quantitatively (Whatman #1 filter paper), quantitatively rinsed with glass distilled water, and the filtrate diluted to exactly 100 m1. Protein was precipitated by the addition of 2 m1 of 10 percent (w/w) lead acetate trihydrate; after pouring off the supernatant from centrifugation, excess lead was removed by incubation of the samples with potassium oxalate (ca 100 mg, crystals) overnight in a refrigerator (4°C). Aliquots free of lead oxalate precipitate (by filtration through Whatman #2 filter paper) were then analyzed colorimetrically for reducing sugars (Dubois et al., 1956). Phenol (0.5 m1 of 10 percent in water, 89 percent stock solution diluted to 10 percent by volume) and concentrated sulfuric acid (5.0 ml) were added to 200 pl of solution containing the nonstructural carbohydrate. Sample color intensity was read on a spectrophotometer at 490 nm against a phenol- sulfuric acid reagent blank, corrected for apparent sugar content of a TNC-extraction reagent blank, and compared to a standard curve of D—glucose solutions. Testing of some samples for color formed by 23 reaction of sulfuric acid and contaminants from the extracts were consistently negative so this correction was not routinely made (Gerchakov and Hatcher, 1972). Structural components of the plant tissue remaining were determined following the general procedure for analysis of forage fiber described by Goering and Van Soest (1970). Tissue samples weighing 250 - 300 mg were refluxed one hour in 50 ml of neutral detergent solution (sodium dodecyl sulfate, pH 7) to remove non-cell wall constituents, followed by similar extraction in acid detergent solution (cetyl trimethylammonium bromide in 1.0 N sulfuric acid). Weight loss between the two extractions is an estimate of hemicellulose content. Lignin was removed from the residue of the detergent extrac- tions by oxidation at room temperature for 90 minutes in a saturated potassium permanganate solution; the cellulose remaining was com- busted in a muffle oven at 525°C for three hours. Content of lignin and cellulose was measured by weight loss between the steps of this procedure. This assay determined the percent of recovered tissue in each of the hemicellulose, cellulose, and lignin fractions. Multiply- ing these data by the weight of the recovered sample gave the absolute mass of each of these fractions remaining after decomposition, which could then be compared to the mass of each present before decomposi- tion to determine the real loss (or gain) of each fraction through time (i.e., [percent component in sample after decomposition X sample final weight] / [percent component in sample before decomposition X sample initial weight] = percent of initial mass of component remaining after decomposition). 24 In Situ Studies Samples weighing 6.0 g of the same dried senescent plant tissue were incubated in various lake habitats in bags made of fiber- glass screen with a mesh opening of approximately 1.5 mm. The bags were about 15 cm square, and in no case were they so full that the plant tissue was unrealistically compacted in the bag. Two bags of each species were tethered to a wood stick about 15 cm apart and placed on the sediment-water interface in the lake with a construction brick serving as an anchor. Periodically the bags attached to one stick were collected and taken, sealed in plastic bags on ice, to the laboratory for immediate analysis of ATP content and ETS activity; weight loss and content of ash, total nonstructural carbohydrates, and fiber components were determined later on the lyophilized samples. All analytical methods were the same as those previously described for the laboratory samples; incubation temperature for the ETS assays was the same as that of the field incubation site. A set of these bags was incubated in Lawrence Lake in the littoral zone on the east shore at a water depth of 2 m during the late spring and summer (beginning 6 June 1975). Lawrence Lake is a mesotrophic hardwater lake with a surface area of five hectares and a moderately developed littoral zone; detailed description of Lawrence Lake can be found in Wetzel et al. (1972). Incubation of a late fall-winter series of bags was begun on 18 November 1975 at three locations: (1) the same Lawrence Lake littoral site where the spring-summer series was placed, (2) in the pelagial zone on the east side of Lawrence Lake at a depth of 7 m, 25 and (3) at a depth of 1.5 meters in the littoral zone on the west shore of hardwater, hypereutrophic Wintergreen Lake (described in Manny, 1971). RESULTS AND DISCUSSION Redox Potential andng The measurements of pH and redox potential made during the laboratory experiments are diagrammed in Appendix Figures 1 through 24. The response of Eh in flasks of the aerobic-to-anaerobic experi- ments quickly showed a drop from initial values of greater than +350 mV to 0 mV in 10 to 25 days at 10°C and within 2 days at 25°C. This drop in redox potential can be attributed to the rapid depletion of dissolved oxygen by microbial respiration as the leachate immediately produced by the rehydrated plant tissue was metabolized. The rate of decline of Eh for any given plant species was not neces-- sarily proportional to the amount of DOC produced (Appendix Figures 25-48). In the strict anaerobic experiements where the media and dry plant tissue were equilibrated in an oxygen-free atmosphere to insure anoxic conditions from the beginning of incubation, rarely was a negative redox obtained shortly after combination of the deoxygenated media and plant tissue (i.e.:itwo hours), although such negative Eh values were obtained in media samples before addition of the plants. Initial positive Eh values in these deoxygenated flasks may have been the result of the immediate solubilization of oxidative compounds from the plant tissue which raised the redox potential of the media. Negative redox conditions were reestablished very quickly in these 26 27 flasks (<:two days at both temperatures). The magnitude of the potentials in the aerobic-to-anaerobic flasks was not very different from those in the strict anaerobic flasks, for all species and at both temperatures; most non-aerated decomposition cultures maintained E values of -100 to ~200 mV. The intensity of reducing conditions h in the anaerobic samples was probably limited by the abundant supply of the alternate electron acceptor nitrate in the media. Because reducing conditions were established so soon after the beginning of decomposition in the aerobic-to-anaerobic experiments, this treatment is considered to be a replicate of strict anaerobic conditions; for that reason, all following discussion relating to "anaerobic" condi- tions will include results from both aerobic-to-anaerobic and strict anaerobic experiments unless the two conditions were specifically different. Oxic conditions (Eh +300 - +500 mV) were maintained by aeration of the flasks in the aerobic decomposition experiments. All species showed a decrease in redox potential in the first 10 to 25 days of decomposition because of high oxygen demand by metabolism of leached organic materials. Flasks incubated at 25°C required about two to four times the volume of air bubbled through the media as the 10°C flasks to maintain highly positive Eh values. The usefulness of redox potentials empirically determined in natural systems has been questioned by Stumm (1966). The major problems stem from interpretation of the measurement. Natural systems are rarely dominated by a single redox system as the elements carbon, nitrogen, oxygen, sulfur, iron, and manganese all have more than one oxidation state in which they can exist. The potential measured by a 28 platinum electrode is a mixture of the potentials of the redox couples present. Further, some couples have no potentials that can be measured electrometrically (e.g. N05 - NOE - NHZ, S0;2 - HS'). Eh’ like pH, is a measure of intensity and indicates nothing as to how well poised the system is, that is, its capacity to buffer or resist change in redox potential. Thus, the magnitudes of Eh values maintained in experiments reported in this study are more a function of the proportions of chemical constituents present than indicators as to what particular redox couples were in flux between oxidized and reduced states. The Eh values are useful, though, to give a general impression of the types of chemical and bacterial transformations that may have been occurring under particular conditions. Under well-aerated conditions, dissolved oxygen acts as the terminal electron acceptor in the oxidation processes, both chemical and those facilitated enzymatically by microorganisms; Eh will be high, relatively. If oxygen is in limited supply, it will be depleted, and experimental studies have shown that redox potential quickly drops (Engler et al., 1976; Reddy and Patrick, 1975). At this point, alternate electron acceptors such as nitrate and sulfate ions become important. The actual oxidation-reduction state of lake sediments is critical to the budgets of many mineral nutrients in the lake (Gorham and Swaine, 1965; Mortimer, 1941-1942). Under reduced conditions decomposition pro- cesses will be incomplete and many nutrients will remain bound in biotic tissue. Oxidizing conditions, on the other hand, cause chem- ical precipitation of many mineralized nutrients. Alternation of 29 oxidized and reduced conditions of the hypolimnion often promotes both decomposition and release of essential nutrients, e.g. phosphorus from the sediments. The role of oxygen in decomposition is complex. Often aerobic and anaerobic pathways of metabolism are compared on the basis of "efficiency," and anaerobism is judged a relatively poor process in relation to aerobic metabolism. This is true if the criterion is the conversion of organic carbon to carbon dioxide with the simultaneous synthesis of ATP, as is frequently the case when dealing with the physiology of individual organisms. However, at an ecosystem level greater diversity and stability of potential pathways of carbon flux result from the existence of anaerobic bacteria. During aerobic metabolism, oxygen serves as the ultimate hydrogen acceptor and is required for stoichiometric conversion of organic matter to carbon dioxide and water. Oxidations occur in the anoxic sediments and hypolimnion of a lake by utilization of other oxidants which can be either inorganic or organic electron acceptors. A gradient of such electron acceptors exists in both space (depth) and time (season) in a lake, and no matter how reduced a particular stratum of the system is, the probability exists for oxidation by some hydrogen acceptor in close proximity (Richards, 1965; Stumm and Morgan, 1970; Whitfield, 1971 101; Rich and Wetzel, 1977). The theoretical products of total decomposition are carbon dioxide and water plus various mineral nutrients. During anaerobic decomposition, although some quantity of these compounds are produced, not all organic material is totally oxidized. While the more volatile 30 products of anaerobic respiration and fermentation such as methane, hydrogen, and numerous short and long chain fatty acids may exist in measurable concentrations in the lower depths of stratified lakes, they are reactive and will be either biologically or chemically oxidized if conditions change so that a more energetically favorable electron acceptor, specifically oxygen, becomes available. Decomposi- tion will then be completed. Hydrogen ion concentrations generally paralleled redox potentials in the same flask (Appendix Figures 1 through 24). Usually the more quickly Eh values dropped in the initial stages of decay, the faster the media became slightly acidic. This correlation could not be made for all species-condition combinations, however; pH and Eh parameters behaved independently in several cases, implying the relationship between the two was not entirely dependent (e.g. Appendix Figures l7, 19). Initial decreases in pH may have been the result of release of acidic organic compounds during leaching, and as oxygen was used as the terminal electron acceptor in the catabolism of these compounds, Eh declined as well. Later in decom- position other organic compounds may have been produced which caused continued reducing conditions but return of the bicarbonate-buffered media to more alkaline pH values. The pH measured in these experi- ments was the net result of the interactions of chemcial buffering systems in the medium and gaseous atmosphere in the flask as well as chemical species put into the system from biological origins: leachate, fatty acid end-products of anaerobic decomposition, carbon dioxide, ammonia, etc. 31 In all cases, pH remained lower in anaerobic flasks (usually 6 - 7) than in aerated flasks (7.5 - 8.5). At 10°C, anaerobic samples showed a continual decline in pH through time while at 25°C, after a decrease at the beginning, pH values increased through the remainder of the experimental period. 0tsuki and Hanya (l972a, 1972b) observed pH changes similar to those just described in their experiments on the decomposition of an alga. In their aerobic decomposition cultures pH increased, which they attributed to presence of undetermined organic compounds. The pH of their anaerobic cultures decreased as a result of production of acetic, formic, and propionic acids. Results of these laboratory experiments fit well the observations made in mesotrophic or eutrophic temperate lakes which typically have lower pH and Eh values in the hypolimnion, especially close to the sediments where decaying organic matter accumulates (cf. Wetzel, 1975:174). However, Reddy and Patrick (1975) found the opposite relationship between pH and redox potential in flooded soil in experimental chambers which were made aerobic and anaerobic alternately by modifying the gaseous atmosphere. Aerated soils had lowered pH values, which they explained as being the result of accumulations of nitrate and sulfate. Anaerobic con- ditions were brought about from bubbling argon through the soil suspension, and the increased pH values observed were thought by these investigators to be due to sparging of carbon dioxide out of the soil- buffering system by the bubbling argon. Such a reaction may have occurred during the current experiments on macrophyte decomposition, 32 explaining the pH being consistently above initial values in flasks aerated with synthetic air (which contained no carbon dioxide). Dissolved Organic Matter Dissolved Organic Carbon Readily soluble constituents of the dried plant material were leached immediately upon rehydration. As microbial populations grew, DOM was not only utilized but also produced, especially as products of anaerobic metabolism. The total amounts of organic matter present in solution over the decomposition periods in this study are diagrammed in Appendix Figures 25 through 48. These amounts repre— sent the net DOC produced by the detritus and its associated micro- flora but which had not yet been converted to microbial biomass or inorganic products of decomposition. Therefore, accounting for different leaching rates of different species under the various con- ditions, the relative decomposition rates of detrital DOM can be estimated as well. In all experiments, the effect of leaching is readily appar- ent at the first sampling date (day 2). The greatest amount of leach- ate was usually produced by Nuphar, followed by Myriophyllum, the two Scirpus species, and least by Najas, The respective maximum and minimum leaching rates of Nuphar_and Naja§_were consistent over all experiments, but the ranks of the remaining three species were variable. Under all conditions except anaerobic at 25°C the concen- tration of DOC declined in the second two-day period of decomposition from the initial leachate peak. During anaerobic decay at 25°C the DOC content continued to increase at the same rapid rate until day 33 10 or 25. This relationship most likely resulted from the inter- action of the effects of temperature on accelerating both leaching and also the rate of microbial production of DOM. At 10°C the initial maximum from rapid leaching was distinct from later accumulations of DOM which resulted from anaerobic microbial metabolism. Aerobically at 25°C leaching was probably just as rapid as in the anaerobic exper- iments (if not more so because of the agitation of aeration), but oxic conditions allowed for very fast, efficient utilization of the DOM and thus no accumulations were seen. Losses resulting from leaching of plant tissue have been widely observed in experimental studies of freshwater and marine macrophyte decomposition (e.g. Planter, 1970; 0tsuki and Wetzel, 1974; Hough and Wetzel, 1975; Harrison and Mann, 1975b; Gallagher et al., 1976) and particularly of allochthonous plant tissue in running waters (Kaushik and Hynes, 1971; Nykvist, 1963). The effects of pre- drying the plant samples might be expected to result in an increase in the quantity of materials leached because of damage to the cell walls during the drying process and therefore greater solubilization during rehydration. This effect was tested in preliminary experiments comparing the quantity and quality of lyophilized versus fresh, senescent tissue of Najas flexilis at 15°C under aerobic-to-anaerobic oxygen conditions. Results showed that the DOC content of media con- taining fresh plants was approximately 50 mg/l and that of dried plants 63 mg/l after two days of incubation. On day 15 there was significantly more DOC in the media of the fresh plants than the dried (200 and 116 mg/l, respectively). By day 32 DOC content was 34 equivalent in the two treatments. UV absorbance and fluorescence remained higher in the dried tissue samples until day 32; pH and redox of the two types were never significantly different. After leaching, which is more a passive solubilization pro- cess than a microbially mediated decomposition, levels of DOM were controlled mainly by the presence or absence of oxygen. DOC con- tinued to accumulate over the entire decomposition period during decay at 10°C without oxygen, but with oxygen only small temporary increases in DOC were observed between days 25 and 50 in Najas, Myriophyllum and Nuphar. At 25°C DOC reached very high levels in the first 25 days in anaerobic experiments, followed by steady decline for the remainder of the experiments. This decline was contrasted to the extremely low concentrations measured over the entire 180 days of aerobic decomposition. The presence of oxygen, regardless of temper- ature, caused only very small amounts of organic matter to be present in solution; higher temperature did promote the eventual decline of DOM which accumulated during early phases of anaerobic decomposition. The effects of aeration were particularly significant with respect to the lower molecular weight fractions. Under anaerobic conditions about half of the DOM which was initially leached passed through a 1,000 MW cutoff filter: this proportion remained constant or decreased slightly throughout the decomposition period at both temperatures. Aerobically, however, the proportion of total DOC that passed through the 1,000 MW filter was much less than one-half, even during the initial leaching period, indicating that these lower molecular weight compounds were very rapidly metabolized when oxygen 35 was present, even at the lower temperature. This proportion stayed low through both aerobic experiments, and the concentrations of lower molecular weight fractions were less variable through time than were the total DOC concentrations. There were no apparent differences between plant species in the proportions of DOM in various molecular weight fractions. Fractionation studies of the organic matter dissolved in natural waters have increased with the development of ultrafiltration technology. Ogura (1974) found maximum DOM in the 10,000 - 100,000 MW range in Tokyo Bay, and Wheeler (1976) narrowed the range of this maximum to 1,000 - 30,000 for Georgia coastal water just off shore from a Spartina marsh. The next most abundant fraction was that of low molecular weight compounds (<:500 - 1,000) followed by higher molecular weights (>t30,000) and then by the largest molecules (>:100,000). This relationship is in contrast to results obtained in a soft-water lake by Allen (1976) where the lowest and highest molecular weight fractions of DOC were greatest, and the least con- centrated fraction was in the midrange of 1,000 - 10,000 MW. Ogura (1975) found that the proportion of low molecular weight DOM decreased during laboratory incubation of water samples from Tokyo Bay. Ultraviolet Absorbance, Fluorescence Determination of the absorbance of ultraviolet light and the fluorescent activity of the DOM was made in these studies in order to detect changes in the qualitative nature of the dissolved detritus produced during decomposition. These assays are relatively non-specific 36 but are particularly useful when interpreted in conjunction with other data. The absorbance of light of wavelengths of 200 - 400 nm is caused mainly by multiple bonds (C=C, C=0) and unshared electron pairs (C-OHZ, C-NHZ) in the organic molecules. These chemical bonds empart to or enhance the color of natural waters. Several organic structures, particularly ring formations, actively fluoresce when irradiated by ultraviolet light (Schnitzer, 1971). These character- istics of dissolved organic matter are being taken advantage of by some investigators in attempts to develop methods which rapidly estimate the DOC content of natural waters based on constant relation- ships between spectroscopic properties and actual 00C measurements (Smart et al., 1976; Lewis and Tyburczy, 1974). Graphs of UV absorbance of DOM of the laboratory experiments appear in Appendix Figures 49 through 72, and fluorescence activity is shown in Appendix Figures 73 through 96. All data were normalized to a per gram initial ash-free dry weight basis (AFDW). Nearly all species under all conditions showed trends in UV absorbance which roughly paralleled the corresponding DOC concen- trations. Generally less UV absorbance was found in DOM of aerobic than in anaerobic flasks, while there was as much or more absorbance in DOM of flasks incubated at 25°C as in those of 10°C. The UV absorbance of the whole fraction (i.e. GS filtrate) increased through time in all species during anaerobic decomposition at 10°C. DOM of experiments of Nuphar, Myrigphyllum, and Najas exhibited absorbance maxima initially due to leaching and either showed constant or increasing absorbance in anaerobic flasks and 37 constant or decreasing absorbance in the aerated flasks. This trend_ was not observed, however, in experiments with the two species of Scirpus, where UV absorbance of DOM increased dramatically in most cases, particularly under the conditions expected to be most con- ducive to decomposition of detrital DOM, namely aerobic at 25°C (compare Appendix Figures 50 and 69). The DOM of lower molecular weight fractions (i.e.< 500, <1,000) showed much less absorbance than would be predicted from the ratio of DOC concentrations in high and low molecular weight fractions. This corresponds exactly to the visual appearance of the filtered samples: fractions of greater than 1,000 MW were definitely colored, depending on the species, ranging from pale yellow-green (Nuphar) through light yellow (both Scirpus species) to deep gold Ngjgé, ,Myriophyllum). Colors were more intense in media from the anaerobic experiments. Low molecular weight fractions ( <1,000) had no visual color in any experiments. Experiments of all species incubated at 10°C anaerobically exhibited constant or slightly increasing levels of absorbance in low molecular weight fractions over time (other than the initial leaching peak and immediate decline). This response is in contrast to that observed under the other conditions where absorb- ance of smaller compounds consistently decreased through time, especially in the aerated flasks, even when absorbance of higher molecular weight fractions was increasing (e.g. see Appendix Figure 66). Fewer trends were discernible in the comparisons of fluores- cence activity of the DOM of the five species under the different decomposition conditions. Generally, high molecular weight fractions 38 maintained fairly constant levels of fluorescence activity over time during decomposition at 10°C; low molecular weight fractions showed little fluorescence activity at 10°C, especially in the aerated flasks where fluorescence by small molecules decreased with time. At 25°C generally all species under all conditions showed slightly increasing fluorescence during decomposition. Again, fluorescence by low molec- ular weight compounds was proportionately greater in anaerobic than in aerated experiments. DOM from Nuphar_had the greatest fluorescence activity, that from S, aggtu§_the least. The non-specific nature of these spectrophotometric assays allows detection of differences in the chemical nature of DOM by comparison of spectrophotometric response with DOC determination under various conditions. Extreme examples of negative correlation between absorbance and fluorescence and the concentration of DOC are shown in Figures 2 and 3. In each case, even though the total amount of organic carbon was present in low or decreasing concentrations, the dominant forms of the organic compounds are such that fluorescence and/or UV absorbance were heightened drastically. In addition, UV absorbance and fluorescence are not necessarily quantitatively related (see Figure 4). Such results are not unique to this study. Wheeler (1976) found that the [DOC]/absorbance ratio was not constant over all molecular weight fractions of water from a salt marsh. The complexity of individual humic molecules and the number and kinds of substituted functional groups that they have will affect not only the wave lengths 39 Figure 2. DOC and UV absorbance of various molecular weight fractions of DOM from flasks containing Scirpus subterminalis during aerobic decomposition at 25°C. 200 40 DOC UV QBSORBQNCE () 1C) 25 ~e nos —-—--oun2 so so onvs 0F DECOMPOSITION -——--——— -—-PM30 - --------- ounos Figure 2 41 Figure 3. DOC and fluorescence activity of various molecular weight fractions of 00M from flasks containing Nuphar variegatum during aerobic-to-anaerobic decompositiOn at 25°C. 42 200 DOC I” O 2 I.“ O (I) III C O 3 ./ f a. ll. ’ .v o /\ \ \ I ’ ’ -“. N / ‘ \ ’- ’ ’ ooooooooo .‘o‘no/v"‘---“‘-~-::’— vvvvv 6 {O is 5'0 9'0 180 DRYS OF DECOMPOSITION * :QS .— — - .PN3O PHlo h — — - —- .U"? .. ————————— .UHOS Figure 3 43 Figure 4. UV absorbance and fluorescence activity of various molecular weight fractions of DOM from flasks containing Scir us subterminalis during aerobic decomposition at 25°C. 44 0.0 0.1 ID 0 V 6- U gga) C .1 O m T“ m ~ 8m eat > D 5'0 9'0 180 so 40 l FLUORESCENCE 20 ~—--—oune so 90 cars 0F DECOMPOSITION -— —— —-Pn30 ~ --------- ounos Figure 4 45 of absorption maxima but the intensity of fluorescence as well (Lévesque, 1972). Both UV absorbance and fluorescence activity in natural waters are caused by the presence of dissolved humic substances or yellow organic acids, which are part of a large family of amorphous, colored substances of complex and highly variable structure (Schnitzer and Khan, 1972; Gjessing, 1976). These compounds, which exist in particulate form as well, are very important in sediment and soil processes (Davies, 1971). Terrestrial decomposition-soil humic matter questions have been well-studied (see reviews in Dickinson and Pugh, 1974). Much evidence indicates that the phenolic and lignin compounds in plant tissue are the major precursors of humic substances (Christman and Ogelsby, 1961; Flaig, 1964). Many non-lignin phenolic compounds are present in plants as well (Bate-Smith, 1962, 1968; Ribéreau-Gayon, 1972). Many compounds Obtained during destructive analyses of humic materials are known to be used in the cellular synthesis of lignin in plants (Christman and Ghassemi, 1966; Freudenberg and Neish, 1968). Flaig (1959) has shown the similar infrared (IR) spectra of lignin extracted from straw, humic acids from decomposing straw, and alkaline extracts of humic acids from marsh soil. IR spectra and comparison of chemical degradation products have been used to show that humic acids of Phragmites peat are made up in significant quantities by aromatic structures that were derived from Phragmites lignin (Farmer and Morrison, 1964). Thin-layer chromatrography of humic acids extracted from soils indicated the presence of relatively unaltered 46 lignin residues of oak and pine trees growing in those soils; lignin residues were not found in the humic acids of clumps of the lignin- free Antarctic moss Bryum argenteum (Burges et al., 1964). Lignin has reportedly been isolated from two species of Sphagnum (Lindberg and Theander, 1952) and the IR spectra of extracts of fresh plants, peat, and humic acids for another Sphagnum species were very similar to each other (Farmer and Morrison, 1964). Evidence also exists to show that lignin is not the only precursor (Christman and Minear, 1971) and that humic-like compounds can be derived from autochthonous and non-vascular plant sources (0tsuki and Hanya, 1967; Nissenbaum and Kaplan, 1972). Several conclusions can be drawn from the data of the present study regarding the control of decomposition of detrital DOM in a lake by environmental conditions of temperature and oxygen concentration. Processing Of DOM occurred faster at the higher temperature which generally caused declining or consistently low concentrations of measured DOC of all molecular weight fractions. In conjunction with the declining total DOC content during decomposition at the higher temperature, fluorescence and UV absorbance of the low molecular weight fractions declined and/or remained at low values. This relationship indicates that these smaller compounds with unsaturated bonds or ring structures were being taken out of solution, either by bacteria or by physico-chemical means such as complexing and adsorp- tion. High molecular weight compounds, however, in spite of decreas- ing carbon content, exhibited increasing UV absorption and fluores- cent properties, indicating an increased dominance in complex 47 humic-type compounds in the organic matter in solution. At the lower temperature decomposition did not proceed as rapidly, as indicated by rates of decline of DOC because Of slow processing. Humic substances persisted in the low molecular weight fractions and did not accumulate in the larger molecular weight fractions. Oxygen was the limiting factor for rapid disappearance of dissolved organic carbon at the low temperature; when oxygen was not present DOM was metabolized only slowly or not at all, and at 10°C even low molecular weight fractions accumulated carbon. The higher temperature eventually caused DOM to be processed despite the lack Of oxygen. When oxygen was present, both small and large molecular weight fractions showed losses in total organic carbon at both temperatures. It is clear that dynamics of dissolved organic carbon in natural’systems depends not only on quantitative aspects but on the qualitative characteristics of the substances as well (cf. Alexander, 1965). Resistant Compounds Humic compounds decompose slowly. Paul (1970) fractionated soil humus into nitrogen-rich materials that had an estimated residence time of 25 years and more resistant humic materials of aromatic struc- ture that had residence times ranging from 200 to greater than 2,000 years. Fokin and Karpukhin (1974) theorize that the products of decaying plant tissue are to a large extent adsorbed by soil humus which is renewed not by formation of new molecules but by additions to currently present molecules. They believe that there is an inert 48 core or nucleus in humic molecules surrounded by more labile func- tional groups which are alternately lost and replaced. The resistance of these recalcitrant compounds to microbial degradation results from their phenolic structure. Alexander (1975) has listed conditions under which microbes will not readily use organic compounds as substrates. Several of these situations are particularly applicable to humic compounds in aquatic environments. Microbes will not readily degrade the large amorphous polyphenolic structures that cannot pass into the cells. Compounds which require exoenzymes from more than one population will not be rapidly degraded. The heterogenity of the structure and functional groups of humic com- pounds may dictate that several different enzymes are needed to facilitate decomposition. However, microbes are fairly specific in the cabilities Of their catabolic pathways (Dagley, 1971, 1975) and the need for different enzymes may translate to a need for several populations. This requirement has a retarding or inhibitory effect if not all of the necessary populations are present at the same place at the same time. In contrast, de Haan (1974) found that a fulvic acid fraction was stimulatory and was degraded by Pseudomonas using lactate as a primary carbon source; this response was attributed to co-metabolism of the two different organic compounds (cf. Horvath, 1972). The diversity of humic compounds present in water is very high. Shapiro (1957) estimated by chromatographic methods that possibly as many as 42 distinct yellow acids could be isolated from ethyl acetate extracts of lake water. If the number of individual 49 compounds is high for a given concentration of resistant DOM, each compound may be present only in small quantities. Many microbes will not metabolize compounds present in concentrations too low to cause enzyme synthesis. Finally, and most importantly, microbes cannot attack a com- pound for which no degradative enzymes exist. Some resistant organics may be the combination of so many biological and chemical reactions that no enzyme exists which can catalyze their breakdown. In addition, humics have an antagonistic deactivating effect on enzymes, e.g. lysozyme (Povoledo, 1972; see also Ladd and Butler, 1975). Some of the resistance of these compounds to microbial degradation can be overcome by changes in the environment in which decay occurs. Waksman and Carey (1935a, 1935b) concluded that sub- strate resistance was partially a function of environmental conditions and could be ameliorated by creating optimal, albeit unnatural, conditions. Thus, the term "resistance" is truly relative and des- cribes how readily macrophytic detritus might be decomposed. Particulate Organic Matter Weight Loss Investigators of decomposition of natural products in both terrestrial and aquatic situations have often mathematically des- cribed the amount of material, nearly always in particulate form, that has "disappeared" or that remains over a period of time. Some decomposition data are fit well by a linear model where unit weight loss per unit time is constant, especially if weight loss due to leaching is ignored, giving a straight line (Mason and Bryant, 1975). 50 Most decay curves in which the leaching component is taken into account indicate that weight loss occurs much faster in the beginning of decomposition than later. For this reason, most Often decay rates are fit well by an exponential function where a constant fraction of the material present at the beginning of a unit of time is lost during that time interval (e.g. Jewell, 1971; Saunders, 1972; Hodkinson, 1975). Reddy and Patrick (1975) used a quadratic equation. Exponential decay is most frequently associated with the decay of radioactive material from one isotope to another by emission of a sub-atomic particle. Since in a given mass of isotope any one atom has just as much probability of decaying in any given period of time as any other atom, the amount of isotope disintegrating in a period of time is a constant proportion of the amount of isotope present. This model fits well, conceptually, the decomposition of physically homogeneous substances, but it is not valid to assume that most biotically-produced material would be subject to a constant rate of loss over time. Plant tissue, consisting of a complex of organic compounds from simple sugars and amino acids to very large and extremely stable structural polymers, certainly would be expected to decay more rapidly in the initial stages than later when the most labile compounds have been removed and only the resistant ones remain (cf. Minderman, 1968). The rate at which the remaining tissue becomes increasingly resistant is dependent on a multitude Of factors: tissue structure, source, and physiological state prior to death, environ— mental conditions, organisms carrying out the degradation, etc. 51 There is no question that application of a simple exponential curve to experimental data and comparisons of resultant decay coeffi- cients have value. Comparisons of such data for similar conditions are Often very informative (e.g. Petersen and Cummins, 1974). However, care should be taken when extrapolating or predicting decay rates outside of the experimental conditions where the measurements were made. Often, a linear or exponential function is used for reasons of convenience; most computers and laboratory calculators are capable of least squares linear regression analysis of raw or logarithmically transformed data. However, this produces the best fit to the trans- formed data, not the raw data, in the case Of an exponential function. A sophisticated least squares curve fitting computer program was used in testing the ability of virtually any selected function to accurately describe weight loss in these experiments. Initially a simple exponential curve was fit to the macro- phyte weight loss data with acceptable results (Table 2), the correla- tion coefficients (r; Observed versus predicted weight remaining) ranging from 0.78 to over 0.99. However, examination of the functions plotted with the actual data pointed out a systematic poorness Of fit, as exemplified in Figure 5a. Even though, in this example, 5 was 0.96, in this and most all other fits of a simple exponential model, the values of the function of best fit were consistently higher than the actual data points during the initial phase of decay, and continually lower than the weights measured during the latter portion of the experiments. This trend indicated that the rate of decay was not constant but was greater initially and then decreased. The simplest 52 Table 2. Decay rate constants of exponential functions Of best fit to weight loss data of aquatic macrophytes under differing experimental conditions. Species Anaerobic Aerobic 2500 0.060 0.085 0.034 0.037 0.028 0.026 0.009 0.017 0.005 0.011 #2222 ' ' , 0.020 0.015 flaZo wiéd 0.009 0.006 42/5‘1gilL/ 0.007 0 007 ' 0.002 0.004 0.002 0.004 52 Table 2. Decay rate constants of exponential functions of best fit to weight loss data of aquatic macrophytes under differing experimental conditions. Species Anaerobic Aerobic 25°C Nuphar variegatum 0.060 0.085 Myriophyllum heterophyllum 0.034 0.037 Najas flexilis 0.028 0.026 Scirpus subterminalis 0.009 0.017 Scirpus acutus 0.005 0.011 10°C Nuphar variegatum 0.020 0.016 Myriophyllum heterophyllum 0.009 0.006 Najas flexilis 0.007 0.007 Scirpus subterminalis 0.002 0.004 Scirpus acutus 0.002 0.004 Figure 5. 53 Graphs of functions (solid lines) of weight remaining over time fit to actual data (triangles) for Najas flexilis during aerobic-to-anaerobic decomposition at 25°C: (a) simple exponential function, k = 0.028, correlation coefficient (Observed vs. predicted weight remaining) r = 0.96; (b) exponential function where k_ is an exponential function as well, a = 0.063, b = 0.049, r = 0.99. See text for explanation of parameters. 54 cod 180 90 I 50 I om ow ow oszHazmm 300a x 1 ON () 10 25 In M A Imw lo 5 Us 2 ..m 4 q 4 0 OOH om 0m CV ON 6 OZHzchmm 30nd x DQYS OF DECOMPOSITION Figure 5 55 function to describe a declining decay coefficient would be a linear one (k = a - bt), but this was rejected because as t_(days of decomposition) increases, the value of the decay coefficient, 5, could theoretically become negative implying an increase in weight remaining. Obviously, while residual weight increases do occur, this characteristic of the model disqualifies it from being applicable in the general case. The next simplest model describing a regularly decreasing decay coefficient is the exponential. An overall weight remaining equation was derived as shown in Figure 6 and fitted to the weight data. Note that this function (Figure 5b) fits the data more closely than does the simple exponential in the example in Figure 5a. This situation was true for nearly all species-experiment combinations. The predicted weight values of the model of best fit and the corresponding decay coefficients are plotted against time along with the actual data in Appendix Figures 97 through 140 for decomposition of macrophytes in both laboratory and field experiments. For com- parative purposes the parameters of the functions of best fit for the aerobic-tO-anaerobic and the aerobic experiments at both temperatures are listed in Table 3. Parameter a_is the decay coefficient at day 0, and parameter b.is the constant proportion by which the decay coefficient is decreased in each time interval. If this model were fit to data for decay of a radioactive isotope, theoretically b_would equal zero, and the proportion of isotope decaying in a unit of time would remain constant. Plant tissue does not decompose at a constant proportional rate: the values of parameters a_and b_vary with both species and 56 Figure 6. Derivation Of exponential function fitted to weight loss data where the decay coefficient is itself an exponential function of time. W = percent of ash—free dry weight remaining; t = days Of decomposition; a, b = constants Obtained by least squares computer fit of function to actual data. The model: dW dk . -bt dt'z -kW, where Ot'= -bt (i.e. k = ae ) Substituting, 01.. -bt dt (ae )W 1_ _ -bt W dW - -ae dt Integrating, In W = 1e"bt + C b Solve for C when t = 0: = -.9 C 1n WO b Substituting for C, -e-bt a 1n W - b e + 1n WO - b . e -bt_ 1nW an0+b( 1) Take antilog of both sides w- %(e'bt-1) - W0 e Final form: a ( -bt Be -1) W = 100 e 57 Table 3. Parameters of exponential functions of best fit to macro- phyte weight loss data where the decay coefficient decreases exponentially with time. a_is the initial rate of weight loss which declines exponentially through time at a rate of O, (From Godshalk and Wetzel, l977b.) Anaerobic Aerobic Species a b a b 25°C Nuphar variegatum 0.1114 0.0692 0.1439 0.0930 Myriophyllum heterophyllum 0.0831 0.0625 0.0619 0.0335 Najas flexilis 0.0626 0.0487 0.0444 0.0244 Scirpus subterminalis 0.0167 0.0145 0.0280 0.0182 Scirpus acutus 0.0138 0.0248 0.0170 0.0103 10°C Nuphar variegatum 0.0436 0.0350 0.0465 0.0451 Myriophyllum heterophyllum 0.0284 0.0328 0.0264 0.0417 Najas flexilis 0.0101 0.0080 0.0148 0.0168 Scirpus subterminalis 0.0003 -0.0193 0.0057 0.0040 Scirpus acutus 0.0791 0.5080 0.0104 0.0219 58 environmental conditions (see Table 3), and it is the interaction of these two constants that give the function its ability to fit the actual data. Initial decay rate, a, is correlated consistently with overall rate Of weight loss, as determined by inspection of the curves and comparing constant decay coefficients, 5, which were estimated by best fit of simple exponential functions (Table 2). The most rapidly decomposing plants had the highest values of a_under all conditions. The values of b_indicate how rapidly the tissue becomes more resistant to decay. The values of the b_parameters are not directly comparable because they are related to the respective a_ parameter values. For example, in the case of Nuphar_during aerobic decomposition at 25°C, the value of b_is very high, but because a_is also high, weight loss was the most rapid of all combinations studied. High Q and b_indicate rapid initial decomposition and moderate rates of continued loss during the latter stages. Moderate a_and low b_ occurred when overall decay rates were fairly uniform for the entire period, i.e. in low leaching situations. Low a_with high Q, as in Scirpus acutus, indicate that leaching, though low compared to other species, was much more rapid than subsequent weight loss and occurred only for a short time. The only exception to the trend of greater values of g_associated with greater overall weight loss rates was that of Scirpus subterminalis. Its values for a_at 10°C were even lower than those of S, acutus, but because its b_values were also extremely low, the average decay rate was greater than for the emergent species. The negative value of b_for S, subterminalis 59 during anaerobic decomposition at 10°C indicates that the rate of decay actually increased with time (Appendix Figure 98). It can be seen that values of S_increased only slightly or decreased with progressively more conducive conditions for rapid decomposition (i.e. anaerobic at 10°C to aerobic at 25°C), implying that decay-resistance of tissue was partially overcome by environ- mental conditions causing decay rates to remain high for a longer time. The greatest increase in a_and S_resulted from increased temperatures, whether aerobic or anaerobic; oxygenation had less effect on the decay rate parameters at either temperature. Weight loss was slowest during the 180-day laboratory decom- position period in the anaerobic flasks incubated at 10°C. Aeration did not appreciably increase particulate weight loss. However, decomposition was much faster at 25°C even under anaerobic conditions, and oxygenation accelerated weight loss somewhat. In most cases during the last half of the decomposition period further weight loss was minimal, and the curves approached very closely some asymptotic limit of minimal remaining weight. Conditions more conducive to decomposition lowered this asymptote but not so far as to result in total weight loss. Rates of plant decomposition for the five species were consistently ranked related to each other over the different experimental conditions: nghgr_was always fastest (i.e. greatest average weight loss per day and least weight remaining at the last sampling period), followed by Myriophyllum, Najas, S, subterminalis, and finally S, acutus. 60 No other studies are known where a decay model with an exponentially decreasing rate coefficient was fit to empirical data, so comparison of parameters is not possible. Few studies have deter- mined simple exponential rates for aquatic decay of vascular plant tissue in the laboratory. Jewell (1971) decomposed 14 species of aquatic macrophytes in aerated cultures at about 18°C and calculated k_values (as percent per day) ranging from 0.052 for Callictriche sp. to 0.18 for Rorippa sp. These values are somewhat higher than those of the present study (see Table 2), but his plants were of species probably with less structural tissue than the plants of this investi- gation. Field studies showed trends similar to those observed in laboratory experiments. Weight loss from in situ litterbags over time was faster in summer where the response was similar for all species to the responses in laboratory aerobic experiments at 25°C, and slower in winter where in situ weight loss was slightly less than that of 10°C laboratory experiments. There were no discernible differences between the two Lawrence Lake incubation sites during the fall-winter experiments. Because curve fits are based on fewer samples in the field experiments, only Myriophyllum and Nuphgr_could be compared meaningfully between the littoral zone incubation sites (Appendix Figures 129 and 139, 130 and 140). In both instances decomposition was markedly faster in hypereutrophic Wintergreen Lake. This result is noteworthy because the littoral sediments of Winter- green Lake are extremely heavily loaded with organics, and strongly reducing conditions always exist. In spite of the seemingly better 61 environmental conditions for decomposition in Lawrence Lake, the faster rates observed in Wintergreen Lake were possibly related to the very active microbial-detrital community of the sediments in this lake. Also, both of these macrophyte species grow abundantly at the incubation site in Wintergreen Lake, and they do not grow at the Lawrence Lake littoral site, so that specific bacteria required for decomposition of either species would be expected to be present in high concentrations in Wintergreen Lake and possibly not in Lawrence Lake. The predicted in situ total weight loss during 180 days for the fastest decomposing species, flgphgr, was 60 to 90 percent and for the slowest, S, gggtgg, it was 20 to 40 percent of initial ash-free dry weight. Tissue of Spartina gynosuroides, Distichilis spicata, and Scirpus americanus all lost about 60 percent of their weight, and Juncus roemerianus leaves, most similar to those of S, acutus of the present study, lost about 40 percent of their initial dry weight during one year of incubation in litterbags in a Mississippi salt marsh (de la Cruz and Gabriel, 1974; de la Cruz, 1975). Leaves of 9:.EEESXI lost 34 percent of their initial dry weight while decaying in litterbags in a Canadian beaver pond (Hodkinson, 1975). Wohler et al., (1975) incubated oven-dried tissue of Potamogeton diversifolius in glass jars with nylon mesh (1 mm openings) lids on the bottom of a pond and observed 57 percent loss in weight during a lOO-day decomposition period. Mason and Bryant (1975) found no significant difference in rates of decomposition of Typha_1eaves in litterbags placed at the edge of reedswamps in two shallow productive English 62 lakes. Total weight loss was 70 to 80 percent over one year for Phragmites, 40 to 50 percent for Typha. Carbohydrates, Fiber Components The results of the carbohydrate and fiber constituent assays are presented in two ways. In Appendix Figures 141 through 184 the content of each component in the decomposing tissue is reported as the percent of the initial concentration, so that the actual gains and losses Of each component can be followed during decomposition. In Appendix Figures 185 through 228 the proportion of recovered tissue that was found in each of the determined fractions is reported, thus making shifts in the dominance of one fraction over another more visible. Total nonstructural carbohydrates (TNC; sugars, starches), present only in low concentrations even initially in these senescent plants, were expected to be susceptible to leaching; therefore, rapid loss of this fraction was anticipated. Anaerobically at 10°C, most TNC levels gradually declined to values about one-half of initial content, sometimes after an early increase over the original content (see Appendix Figures 141-184). Aeration at 10°C caused much more rapid decline of the original TNC content in all species, and losses of TNC during these experimental conditions were very similar to those of anaerobic decomposition at 25°C. Aerobic decay at 25°C did not result in the expected rapid decrease to immeasureable levels, and the continued absence of these compounds for the duration of the experiment. Instead, the trends were very similar to those seen in previously described experiments: gradual but continual decline 63 through time and much dependence of rate on species. Under all experimental conditions, Nppppr_continually lost its TNC faster than did the other species. Losses of TNC by Myriophyllum and Ngjp§_were also rapid and usually faster than occurred in the Scirpus species. However, in many instances the two bulrushes were devoid of measurable TNC sooner than were the two submersed plants, particularly under aerated conditions. The initial high levels of TNC in Najp§_were probably concentrated in the many nearly mature seeds in the axils of the leaf material. Changes from initial TNC content in the field-incubated samples showed the same species—dependent rate characteristics, but overall losses occurred more slowly and, except during summer incuba- tion, TNC levels did not drop as low as in the flask experiments. TNC contents of winter field samples were much like those of the 10°C anaerobic samples. Structural carbohydrates constituted the majority of the biomass of the plants and were nearly always present in large amounts at the end of the incubation period. The material that was assayed as lignin was very resistant to decomposition, and this fraction usually showed an increase over initial content during at least the beginning of the decomposition period. Under aerobic-to-anaerobic conditions at 10°C the proportions of hemicellulose, cellulose, and lignin in the recovered plant material remained approximately constant in all species. Structural carbohydrates gradually decreased through time. The lignin fraction increased by as much as two to five times over the initial concentration in the two Scirpus species and Nuphar, 64 while the proportion Of lignin in Najas and Myriophyllum increased only slightly. Greater increases in the lignin fraction and less overall loss of hemicellulose and cellulose were observed from S, subterminalis and Myriophyllum in the strict anaerobic experiment at 10°C. Aeration at 10°C caused a more rapid loss of the structural carbohydrates, and the proportion of lignin in the recovered plant tissue subsequently increased through time. This increased concen- tration was the result of the presence of nearly constant masses of lignin fraction, at or above initial levels (except in ijgg) for the entire experiment. Hemicellulose and cellulose decayed to about one- third their original contents in Npphar, Myriophyllum, and Ngjpé, and to one-half in both species of Scirpus. At 25°C during anaerobic decomposition, the lignin fraction decreased very little during the entire 180 days, and real increases in this component above original levels were not substantial. Under these experimental conditions, however, cellulose and hemicellulose decayed much more quickly than at 10°C. Aerobically at 25°C, hemicellulose and cellulose decreased to less than half of their initial amounts within 25 days in Nppppp, Myriophyllum, and Najas, and decreased only very slowly thereafter. These constituents in both species of Scirpus did not decline as fast initially and continued to be decomposed over the entire time of the experiment. Even under these conditions, the lignin fraction was exceptionally resistant, and there was always nearly as much or more than the original amounts of lignin-like material in all species except ijgg, Thus, the lignin component dominated the fiber con- stituents of the recovered macrophytes by the end of decomposition 65 under warm aerobic conditions in all species except S, subterminalis and S, acutus. Lignin-like materials made up over 30 percent of the ash-free dry weight of Myriophyllum and over 20 percent in Najas and Npphpg, in the last samples that had enough tissue to analyze for fiber. Field-incubated samples exhibited trends similar to those of the laboratory samples. There were no discernible differences in structural constituents between the three sites of fall-winter incuba- tion; rates of change of component concentrations were greater during the spring-summer experiment for most species. The data from TNC and fiber assays, when reported either as percent of initial content or percent of recovered ash-free dry weight Often appear erratic. Surely in some cases there was much random variability in the plant tissue that was used as substrate, the organ- isms responsible for decomposition, subsampling and assay procedures, etc. However, the data were often remarkably consistent. All fiber data, reported as percent of sample weight, for Scirpus acutus samples incubated in litterbags are presented in Figure 7. The magnitudes and trends through time of each of the four components were very similar for all incubation conditions. The consistency of such subtle responses under widely diverse conditions of decay is an indication of the importance of considering species effects in decomposition studies. Presumably some of the uniformity of this particular species during decomposition is because of its decay-resistant structure and resultant slower alteration. 66 .cowpmcmraxm com axmu mom .Lmucwz .m:o~ FmLOppwp axe; cmmgmemucwz A00 mempcwz .mcoN —ewmepma oxeA mucmc3e4 A00 ”gauze: .mcoN FmeopuwF axe; mucmezm4 ADV ”gossam .m:o~ _meopuw~ wxmA mocmLZm4 Aev ”meowpwccou 020» Love: cowuwmanoomu :pwm cw meweau magnum mzmgwum mo .300< umem>oumc mo ucmucma mm .mucwcoasou AoHAV cwcmwp use .Aguuv mmoF3FFOO .Azsz mmoP3PP00wEm: .Aozpv mmpmguxsoncmu Fmezpusgumco: peach .n mgzmwm SlNBNOdHOO 838K! 1N3383d 09 s; 0;. 91 0 § 3 11 1 II ' . l I I I . ,8 I h I I . I . .. \ l l ’1‘ ‘ .g; . /P2 V V4 4 ‘ o a S! 01 S 0 0N1 1N3083d SIN3N0dW03 83815 Iwaaaad 9 5g 0;: S} o 444 Io 2°. 1 I l I I I 90 SO 0e ‘9': 0'1 owI Iwaoaaa 67 SLNBNOdHOO 83815 1N3083d 09 s} as 9.1 O :8 3 I l . I , I I I ’ I I I o 1 E0) ‘ I ‘ l I I I i ' o I] I ’m ' l I ,, (I I | I2 T \V 'o 06 SI 01 S 0 0N1 1N3083d SLNBNOdHOO 83813 IN3383d 09 9y 033 9.1 O O s Q |I 1 II I I '8 I II I II . I m I) | /I It I 17 2 I 1 'O 08 ST 0! S 0 0N1 LNBOUBJ DRYS OF DECOMPOSITION DRYS OF DECOMPOSITION -—~—-—-—mu --——~um -—-— — — —-'/.HEM ~—~ZTNC Figure 7 68 The conclusion to be drawn from these data on the decomposi- tion of macrophytic fiber is that plant decay dynamics are unique to each species. The initial content of hemicellulose, cellulose, and lignin, and the sum of these individual concentrations are listed in Table 4 by species in order of decreasing rate of plant decomposition. The high fiber content of flgjpg, which decomposed at rates similar to those of Myriophyllum samples, was probably the result of high content in the leaf material of many seeds whose protective coats were resis- tant to breakdown during fiber analysis and caused an overestimation of the cellulose fraction. It is noteworthy that Scirpus subterminalis, which grows totally submersed for its entire life cycle, did not decompose as the other submersed plants did but apparently retained the structural characteristics of its genus of emergent bulrushes and decayed much as did Scirpus acutus. These data concur exactly with those of Polisini and Boyd (1972) who measured the non-cell wall material in 21 species of aquatic macrophytes and Obtained these averages for the three major growth forms: submersed 53.4, floating-leaved 66.6, and emergent 33.7 g non-cell wall material/100 g dry weight of plant tissue. By subtraction, the average percentages of the cell-wall material in the respective forms are obtained as 46.6, 33.4, and 66.3. These data indicate that the floating-leaved plants contain the least amount of structural tissue, followed by submersed and then emergent plants. It can be seen that the concentration of no single component correlates as well with decomposition rates as does the total fiber content. In spite of the high resistance of lignin to degradation, 69 Table 4. Initial content of fiber components (as percent of ash-free dry weight) of senescent macrophytes. (From Godshalk and Wetzel, 1977b.) Species ce'fifllgse Cellulose Lignin Total Nuphar variegatum 12.3 17.6 4.8 34.7 Myriophyllum heterophyllum 10.3 17.3 4.7 32.3 Najas flexilis 20.0 31.6 8.4 60.0 Scirpus subterminalis 34.6 26.4 2.6 63.6 Scirpus acutus 32.3 33.7 3.8 69.7 70 its concentration apparently did not totally regulate the decomposi- tion of plant material. Hence, the fiber components which constitute the major part Of macrophytic biomass are probably the most resistant components of this tissue, and rates of decomposition of whole plant material may be a function of the amount of these components initially present. Not only is the polymeric and/or aromatic structure of these individual compounds less readily broken down, but also some com- pounds affect the decomposition Of others by the way they are associated with each other in the tissue (Cowling and Brown, 1969). Microbes will not readily degrade compounds in which the sub- strate or bond to be attacked is not accessible. The highly cross- 1inked structure of lignin (Schubert, 1965:34), and presumably of its derivatives, makes them less vulnerable to enzymatic attack. Nickerson (1971) suggested that degradability of a compound such as lignin may be related to the geological time it has been avail- able as a substrate, comparing relatively old and degradable cellulose with the more recent and resistant lignin. Lignin is decomposed by some organisms, mostly basidiomycete fungi (cf. Christman and Ogelsby, 1971). The two enzymes most implicated in the degradation are pheno- lase and laccase, both oxidases that catalyse the oxidation of their substrates by molecular oxygen; they will not function in anaerobic conditions (Schubert, 1975:79). Recent studies using radioactively- labelled lignins demonstrated decomposition of lignin to carbon dioxide in numerous aerobic habitats and the rates of oxidation were related to temperature and concentration of carbon, nitrogen, calcium, 71 and potassium at the incubation site (Crawford and Crawford, 1976; Hackett et al., 1977). Few investigators have examined the dynamics of the fiber fractions of decomposing aquatic macrophytes. de la Cruz and Gabriel (1974) reported that the crude fiber fraction of Juncus roemerianus declined from 39.4 percent of ash-free dry weight of "standing dead" plants to 9.1 percent during various stages of decomposition. Carbo- hydrates (measured as nitrogen—free extract by an unnamed solvent) decreased from 52.4 to 11.3 percent. In a similar study (de la Cruz, 1975) it was found that crude fiber decreased from 34.2 to 12.5, 31.5 to 10.0, and 29.9 to 6.4 percent, respectively, in Spartina gynosuroides, Distichlis spjcata, and Scirpus americanus during decomposition for 12 months in litterbags. Corresponding changes in carbohydrate for the same species were 49.6 to 35.0, 53.1 to 39.8, and 50.8 to 11.3 percent respectively. These carbohydrate values were determined by a method differ- ent from the one used in the present study and are not comparable. McIntire and Dunstan (1976) used the same enzymatic assay for carbo- hydrate as was used in this study to analyze living tissue of Spartina alterniflora. They measured values in the range of 4 to 10 percent of total dry weight as TNC. The measurements are only slightly higher than those found for senescent freshwater plants of the present study. The low concentrations of TNC observed in the present study may be partially due to incomplete degradation of the carbohydrates during analysis. When this enzymatic assay was performed on lotic alloch- thonous leaf litter, the enzyme was found to complex with humic 72 compounds present, severely reducing the effective enzyme concentra- tion (M.J. Klug, Kellogg Biological Station, pers. comm.). Such an effect is likely to have occurred in the analysis of TNC of decompos- ing macrophytes as well. Other investigations by Fleischer and Larsson (1974), Park (1974), and Kormondy (1968), and others have examined the decomposi- tion of various forms of pure cellulose. These studies have limited value since the decomposition of filter paper, cotton thread, or cellophane in natural waters bears little relationship to the degradation of natural plant materials. Microbial Metabolism Monitoring the concentrations of various components of decomposing macrophytes and the related production of DOM is informa- tive Of the fate of plant tissue in the littoral zone but not of the means by which this fate is achieved. Measurement of the ATP content and the dehydrogenase activity of the detrital-microbial complex were used as direct assessments of the activity of the decomposition processes occuring under the various experimental conditions. The data obtained from these measurements are presented in Appendix Figures 229 through 272. ATP Content Theoretically, the ATP content of detritus is an approximation of living microbial biomass associated with the detrital material since ATP is not stored in significant amounts by living cells, and it breaks down very quickly upon cell death (Holm-Hansen and Booth, 73 1966). Although ATP determinations have been performed mostly in natural waters on planktonic organisms, investigators have applied the technique to measure the ATP of microorganisms associated with the detritus and sediments (e.g. Lee et al., 1971; Holm-Hansen and Paerl, 1972; Asmus, 1973; Karl and LaRock, 1975; Bancroft et al., 1976; see review by Laake, 1976). The ATP content of the microflora associated with decaying Nuphar, Myriophyllum, and Najas attained maximum values after about 25 days and then declined slowly during the remainder of anaerobic incubation at 10°C. Both Scirpus species maintained only very low contents of ATP for the entire period. At 25°C and under anaerobic conditions, ATP levels were somewhat greater among all plant species than at 10°C. Aerobic decomposition resulted in greater con- centrations of ATP. In Nuphar, Myriophyllum, and Ngjgg, ATP levels again reached maxima at about day 25 and then declined; levels asso- ciated with S, subterminalis and S, acutus were low initially but continued to increase for the duration of the experiment. Levels in aerobic flasks were higher than those in anaerobic flasks at 25°C, and highest levels often occurred in a sharp peak within the first ten days of decomposition. Only during aerobic decomposition at 25°C were differences in ATP content detectable among plant species. Ngj§§_and Myriophyllum exhibited maximal ATP contents about four times greater than those of S, subterminalis and Nuphar, but the latter two species maintained substantial levels over the entire study period so that ATP contents for the four species were probably not different if averaged over 74 time of decomposition. S, gpptpS, the most fibrous and slowly decaying plant, consistently had much higher ATP content than the other species, implying a higher microbial biomass associated with this resistant plant. Litterbag samples were characterized by having very constant ATP levels compared to laboratory samples during the entire incuba- tion period. Values for laboratory and lake incubation were generally of the same magnitude, and no consistent differences between species were observed. Except in the spring-summer series where samples taken after day 25 usually did not contain sufficient tissue for ATP extraction, ATP levels rose slightly from the beginning to peak amounts at about day 40 and then declined before the last sampling on day 128. The dependency of the results of this assay on sample type and efficiency of extraction and enzymatic determination preclude comparison to absolute quantities of ATP found by other investigators. Also, both laboratory and field samples were exposed to abundant supplies of calcium carbonate and humic compounds, both of which have been found to interfere with the determination of ATP (Cunningham and Wetzel, 1977). For this reason, present ATP values are not comparable to those of other studies, and may vary within this study because of the variations in humic matter content of samples of differing plant species and incubation conditions. Pamatmat and Skjoldal (1974) measured ATP in marine coastal sediments and found consistently lower ATP content at greater depths of sediment. Presumably, the implied decrease in microbial biomass in 75 the lower layers of sediments is caused by the concentration of dis- solved oxygen and the proportional reducing conditions there, accum- ulation of end products because of poor flushing and impeded diffusion, increased predominance of resistant organic substrates, etc. These are all conditions that were probably occurring in the decomposition flasks in this study and might explain the consistent decline in ATP during the latter stages of incubation among the rapidly decomposing species. In flasks containing resistant species of macrophytes, these conditions were established only slowly, thus allowing microbial ATP levels to increase for a longer time. Olah (1972) observed an increase in ATP during the first five days of laboratory decomposition of ground Phragmites and then decreasing values. ETS Activity_ Whereas ATP has been proposed as an estimate of microbial biomass, assays of the activity of microbial electron transport systems have been used to estimate the actual respiratory activity of cells. The assay supposedly is a measure of the activity of dehydrogenase enzyme which is a participant in a portion of the metabolic electron transport system that is common to aerobic and anaerobic organisms alike (Curl and Sandberg, 1961; Zimmerman, 1975). Ecologists have used this assay to estimate respiratory activity of both planktonic and benthic aquatic and marine organisms. In this study, under anaerobic decomposition at 10°C, ETS activity increased throughout the decomposition period among all species except for S, gpp§p§_which decreased after 50 days. ETS activity was lower for S, subterminalis, Myriophyllum, and Najas under 76 aerated conditions at 10°C, but activities for Nppppg_and S, pppgp§_ reached very high levels after 50 days and then declined. High ETS activity was observed intermittently during anaerobic decay at 25°C, but there were no trends in the changing values. Again, Npppg[_had the greatest maximal activity of all species. The ETS levels of aerated samples at 25°C were lower than the anaerobic ones and approx- imately the same as those from 10°C aerobic conditions. For all species, ETS activity was greatest during the first 25 days and then declined steadily. In the study of Olah (1972) mentioned above, dehydrogenase increased initially (to day 9) and then declined. Interpretation of the results of the ETS assay is particularly difficult. In all species, ETS activity was considerably higher under anaerobic conditions than aerobic, thus implying a chemical reduction that was not necessarily dependent on biotic respiratory activity (see also Pamatmat, 1975). It has also been shown that reduced humic compounds, which obviously are present in large amounts in decomposing plant tissue (especially anaerobically), have the potential to provide electrons and thereby reduce the tetrazolium salt used as the colorimetric alternate electron acceptor in this assay (Schindler et al., 1976). Because of this interference and the role of humic compounds, which can be reversibly oxidized and reduced and thus participate in aquatic electron transport systems, the ability of the ETS assay to assess strict biological respiratory activity has been questioned (A. Zimmerman, Univ. Toronto, pers. comm.). In the present study ATP content did not correlate with ETS activity, and the values obtained by each assay varied independently. 77 Pamatmat and Skjoldal (1974) also measured ETS activity in their investigation of sediments and found it to decrease with increasing sediment depth as well. The ratio of ETS/ATP increased significantly with sediment depth, suggesting to the authors the possible existence of a gradient of microbial species or metabolic types in the sediments. Knowledge of the quantiative aspects of microbial metabolism in aquatic ecosystems is crucial to understanding them, and certainly much more effort must be applied toward accurately obtaining such information. Nitrpgen and Decomposition Nitrogen serves in several critical processes of the metabolism of the littoral zone. Various inorganic forms of nitrogen are present in different proportions depending on redox conditions and pH. Organic nitrogen exists mostly as protein or protein subunits. Inter- conversion of these forms is mediated by several groups of micro- organisms which variously oxidize or reduce nitrogen compounds. Despite the abundance of molecular nitrogen in the atmosphere, low concentrations of dissolved nitrogen can limit productivity in aquatic ecosystems. Nitrogen is needed by living organisms as a protein constituent; unavailability of nitrogen, either by total lack of the element or by its being present predominantly in a form that is difficult to metabolize, limits protein synthesis and, in the case of microorganisms, results in declining populations over time. Much of the decomposition of polymerized carbon of macrophytic origin undoubtedly occurs by extracellular enzymes, requiring a large 78 synthesis and secretion into the habitat of organic nitrogen by microbes (cf. Kim and ZoBell, 1974). Because of the importance of nitrogen to the metabolism of lakes in general (Kuznetsov, 1975:259; Wetzel, 1975:186) and its role in decomposition processes in particu- lar, changes in the amounts of total nitrogen, both in particulate and dissolved forms, were monitored during decomposition of macro- phytes. Particulate nitrogen and carbon, as percentages of total dry weight, of recovered macrophyte tissue are shown in Appendix Figures 273 through 316. The percentages by weight of nitrogen and carbon in the residue of lyophilized media (i.e. inorganic salts plus DOM) are reported in Appendix Figures 317 through 340. Particulate Nitrogen During anaerobic decomposition at 10°C, the proportions of nitrogen and of carbon in the plant tissue remained fairly constant in the two species of Scirpus, yielding constant C:N ratios through time. The less resistant species, especially Npppgp, exhibited increased percentages of nitrogen associated with the POM as decomposi- tion proceeded. At the same time, C:N values decreased as carbon levels remained constant. Aeration of the 10°C flasks caused increases in nitrogen in all species except S, ggptpé; the greatest increase was again in Npppgp_and the least in S, subterminalis. Under these conditions, as in the 10°C anaerobic experiments, the overall net increases in percentage nitrogen followed temporary losses of nitrogen in the first two to ten days of incubation of Npphar, Myriophyllum, and flgjpg, The Scirpus species attained minimal levels of nitrogen 79 only after a longer period of up to 50 days. These results indicate that the two species of bulrush lost less nitrogenous DOM by leaching than the other species which contained greater proportions of non- cell wall tissue. Aerobic incubation at 25°C resulted in overall increases in nitrogen in both the Scirpus tissues similar to those of the more flaccid species during cold incubation. These less resistant species, however, showed very steep increases in percent nitrogen during the first 25 days of decomposition at 25°C, and then declines of particu- late nitrogen. Thus, the C:N ratio continually decreased in S, sgbterminalis and S, acutus, but in Nuphar, Myriophyllum, Najas the ratio reached minimal levels at about day 25 and then increased. The proportions of nitrogen in the particulate detritus increased very rapidly to maximal levels within four to ten days in all species except S, pgptp§_which increased continuously. Following these rapid increases, nitrogen levels remained constant or declined, and the resultant C:N ratios were stable once minimal values were reached. The response of particulate nitrogen in litterbag samples incubated in summer behaved as for the 25°C aerobic flask samples: percentage nitrogen increased for the first 10 to 50 days and then declined in all species except S, gpptp§_which showed an increase in the latter 150 days of decomposition. During fall-winter incubation, percentage nitrogen in all species usually increased to maximal values within the first 10 to 25 days and then decreased, but the changes in both Scirpus species were smaller than in the other plants. Percentage nitrogen values were generally higher for plant samples 80 incubated in eutrophic Wintergreen Lake than those in oligotrophic Lawrence Lake. This difference was attributed again to the greater microbial activity of Wintergreen Lake sediments at the incubation site. No apparent differences in response were found between the two Lawrence Lake incubation sites. Dissolved Nitrogen Without exception by any species, the proportion of nitrogen in the dissolved matter of the media decreased rapidly to very low levels during decomposition at 10°C (dissolved nitrogen data are in Appendix Figures 317-340). Under anaerobic conditions Myriophyllum, Npppgp, and S, gpp§p§_either showed slight increases or no change over initial concentrations after the first two days of decomposition, but in the other two species nitrogen began to decrease immediately. Anaerobically, the percentage dissolved nitrogen remained low in media of all species. Aeration caused levels of dissolved nitrogen in S, subterminalis and S, ggpppg flasks to be continually slightly higher than at 10°C and in Npphar, Myriophyllum, and ij§§_the per- centage nitrogen showed increases later in the incubation period although initial levels were never reached again. During anaerobic decomposition at 25°C, percentage dissolved nitrogen again decreased quickly and was maintained at constant levels which were lower than those of aerobic flasks at 10°C. Highest proportions of dissolved nitrogen were found in the 25°C aerated flasks. Flasks of both species of Scirpus had the greatest proportions of nitrogen in the dissolved matter, followed closely by Nuphar, Myriophyllum, and Najas 81 during anaerobic conditions. Aerobically, S, acutus had the most dissolved nitrogen, and again Najas the least. Discussion It might be expected that a negative relationship would have existed between dissolved and particulate forms of nitrogen based on leaching and microbially mediated conversions. The data however do not necessarily support such a conclusion. Increases in particulate nitrogen were not necessarily accompanied by decreases in dissolved nitrogen, and vice versa. These data are reported as percentages of the dry weights of the particulate and dissolved fractions rather than actual masses of nitrogen, and are not corrected for ash content. Values of percent nitrogen in the residue of the media could change drastically without changes in the actual content of dissolved nitrogen just by variations in the mass of other substances, particu- larly DOM. No attempt was made to convert these proportional data to absolute units. These data represent the net result of several pro- cesses occurring between sampling days and do not reflect the magni- tude of total nitrogen flux among the many pools present (inorganic, organic, particulate, dissolVed, gaseous). For example, values of particulate nitrogen rarely exceeded 100 percent of the amount present initially. That is, in almost all cases, peaks in percentage nitrogen of recovered particulate macrophyte tissue do not represent absolute increases in nitrogen content. This does not mean that particulate nitrogen was not added to the detrital material; it does indicate that there was a net removal of nitrogen from particulate form, even 82 when this removal was less than the net loss in weight, i.e. when percentage nitrogen was increasing. In other words, whole tissue often decomposed at a greater rate than the particulate nitrogen fractions of the tissue. Many investigators have encountered increases of nitrogen in decaying plant tissue in soil decomposition studies (e.g. Tenney and Waksman, l930; Sowden and Ivarson, l959; Anderson, l973),studies of decay of allochthonous plant tissue in streams and rivers (Kaushik and Hynes, l968, l97l; Hynes and Kaushik, l969; Mathews and Kowalczewski, 1969; Iversen, l973, Triska et al., l975), and aquatic macrophytes in lakes and marshes (0dum and de la Cruz, l967; Boyd, 1970; de la Cruz and Gabriel, l974; de la Cruz, l975; Mason and Bryant, l975; Hodkinson, l975; Hunter, 1976). Consistent losses of nitrogen from decomposing plant tissue have been reported as well (e.g. Tenney and Waksman, l930; Kaushik and Hynes, l968; Harrison and Mann, l975a, l975b). Nearly always the increase in nitrogen in the detritus is attributed to accumulation of protein in the form of microbial bio- mass. Kaushik and Hynes (l97l), using anitbacterial and antifungal antibiotics in cultures of decomposing leaf tissue determined that nearly all of the protein increase that occurred was the result of fungal biomass and little was in the form of bacteria. However, there was an increase in total percentage nitrogen (protein plus other) even in the treatments receiving either antifungal 0r antibacterial antibiotic or both, indicating that there was another source of nitro- gen partly responsible. Gosselink and Kirby (l974) calculated the 83 increase in mass of microorganisms associated with decomposing Spartina alterniflora based on probably invalid assumptions that nitrogen as percent of ash-free dry weight remained constant during decay in each of the microbial and plant fractions. Nevertheless, as Spartina lost weight over time the biomass of microorganisms,computed from particulate nitrogen data,increased,and respiratory measurements (i.e. oxygen consumption) correlated well with estimated microbial biomass values. de la Cruz and Gabriel (1974) also observed parallel increases in proportional nitrogen content and oxygen consumption in finely ground detrital tissue of guggu§_decaying in the laboratory. The assumption that observed increases in nitrogen content occur as microbial protein is often made without corroborative data, and there is evidence that associated microbial biomass may not account for all increases in detrital nitrogen during decomposition. Harrison and Mann (l975a) determined both total nitrogen and trichloroacetic acid-insoluble nitrogen. In dead, fallen Zostera marina leaves non- protein nitrogen accounted for over half of the total nitrogen. Green and living senescent leaves contained greater proportions of non- protein nitrogen. Iversen (1973) studied the decomposition of beech leaves in a stream and found that in the first month of decomposition nitrogen (percent of AFDN), bacterial numbers, fungal and algal biomasses, and oxygen consumption all increased. By converting bacterial numbers and fungal volumes to units of mass he estimated the absolute amount of nitrogen in the microbial community associated with the leaf material, and it amounted to only l to 4 percent of the total leaf nitrogen. 84 Iversen suggested that the majority of the nitrogen increase was "released and deposited" by microorganisms. A similar conclusion was made by Suberkropp et al. (l976) who measured absolute and pro- portional increases over time in nitrogen content of the lignocellulose fraction of decomposing oak and hickory leaves. Since true lignin compounds theoretically contain no nitrogen, such increases in the presence of nitrogen in this fraction were attributed to complexing ("tanning") of microbial exoenzymes by phenolic compounds abundant in both the plant tissue and the surrounding water. Ulehlova (l97l) discovered significant increases in C:N values of humic fractions of decomposing tissue of the macrophyte Stratiotes aloides. There is much biochemical evidence to justify the idea of such complexation of nitrogenous and polyphenolic-lignin compounds (e.g. Handley, l954; Flaig, 1964; Feeny, l969; Haslam, l974; see review by Ladd and Butler, l975). Data of the present study can be interpreted as supporting the microbial biomass explanation of increasing nitrogen content. The consistent increase in the proportion of particulate nitrogen during anaerobic decomposition at l0°C paralleled accumulations of DOM and slow weight loss. Under conditions more conducive to decay the pro- portion of particulate nitrogen increased faster, particularly in the faster decomposing plant species. Particulate nitrogen decreased again at about the same time that weight loss rates began to decrease, implying a decline of microbial populations as the plant substrates became more resistant to microbial conversion. 85 It should be remembered that most described increases in nitrogen are actually increases in the proportion of nitrogen in residual substrate. This may be the result merely of differential decomposition rates where weight loss is due more to mineralization of non-nitrogenous constituents in the detritus (cf. Minderman, 1968). There are many cases of increases in absolute nitrogen content of detritus and these, as well as increases in the mass of the lignin- like fraction of POM, might be explained together by complexing of protein and phenolic compounds. Surely both microbial biomass and complexation account for increased predominance of nitrogen in the biomass of decomposing plant material. It is important that future studies deal with both of these processes as they have very different implications in the ecosystem. If accumulated nitrogen occurs largely in the form of microbial pro- tein it is indicative that conversion of both carbon and nitrogen are occurring via microbial catabolism of plant tissue. Further, the microbial protein associated with the detritus is usually considered a significant food source for aquatic detritivores. On the other hand, complexed enzymes represent a dead-end or at least a severe obstacle to complete mineralization of organic matter and a wasted expenditure of energy and nitrogen by decomposers. A complicated relationship exists between the abundance and form of available nitrogen and decay rate of plant biomass. Waksman and Carey (1935b) discovered that the decomposition of glucose in seawater was controlled by the amount of nitrogen (added as ammonium sulfate) in the water, to a certain point where excess nitrogen no 86 longer accelerated decay. If more glucose was added at this point, both bacterial numbers and oxygen consumption increased. Addition of glucose without excess nitrogen did not increase microbial activity. Hynes and Kaushik (l969) found that elm leaves, which gain nitrogen during decomposition (Kaushik and Hynes, l968), showed increased weight loss when any form of nitrogen was added (i.e. nitrate, ammonia, or animal protein). More resistant leaves of oak and alder, which had decreasing nitrogen concentrations in the earlier study, required either more of the reduced form of nitrogen or higher tem- peratures in order to show faster weight loss. Greater concentrations of nitrogen in solution increased apparent protein associated with the elm leaves, but did not always do so for oak and alder leaves. Triska and Sedell (l976) fertilized replicate experimental streams with different levels of nitrate-nitrogen and observed no significant differences in decay rates or nitrogen accumulation of the leaves in the different streams. Addition of nutrients (nitrogen, phosphorus, potassium) to cultures of decomposing crop-plant tissues always accel- erated weight loss (Waksman and Tenney, 1928). Many other examples exist in the literature of agricultural and woodland soil decomposi- tion studies where plant species behave oppositely with respect to nitrogen gain or loss during decomposition. It is generally agreed that the initial content of nitrogen of plant tissue itself has much to do with how fast it will be decomposed and that plant tissues with higher initial levels of nitro- gen will be broken down faster. Polisini and Boyd (1972) determined that floating-leaved and submersed macrophytes had greater content 87 of nitrogen than emergent plants. Hodkinson (1975) observed that after a month of incubation an inverse correlation existed between the C:N values, which had stabilized by then, and the rates of decom- position of five species of plant tissue in a pond. Initial nitrogen content also influences whether nitrogen will be consumed or liberated in the decomposition process. Tissues with a low initial C:N release nitrogen on decomposition and tissues with high C:N ratios require nitrogen from a source other than the substrate (Waksman and Renn, l936). Parnas (l975) developed a mathematical model to describe decomposition of organic matter with special emphasis on nitrogen fluxes. The conclusions reached were that nitrogen is not needed and has no effect on the decay of materials already containing relatively high amounts of nitrogen (C:N less than critical value of 20 to 30), and that nitrogen will be released as a result of decomposition. Materials with initial values of C:N greater than the critical value will respond to outside additions of nitrogen with increased decay rates and decreasing C:N values during decomposition. Based on the obviously complex and sometimes seemingly contra- dictory interactions of nitrogen and plant decomposition, the results of this study are best generalized as follows. The fastest decompos- ing plant, fluphag, had the greatest initial concentration of nitrogen in its tissues, as seen in Table 5. Over all environmental conditions investigated, tissue weight loss rates were correlated with initial nitrogen content. Correspondingly, faster decomposing plants had lower C:N ratios. The nitrogen and carbon content of senescent 88 Table 5. Initial nitrogen and carbon content (as percent of total dry weight) and the C:N ratio of senescent macrophytes. (From Godshalk and Wetzel, l977b.) Species Nitrogen Carbon C : Nuphar variegatum 2.4 39.3 l6.6 _Myriophyllum heterophyllum 2.0 24.7 l2.2 Najas flexilis l.8 3l.2 l7.8 Scirpus subterminalis l.2 30.4 25.7 Scirpus acutus l.5 43.6 29.9 89 macrophyte tissue, along with the C:N ratios, are listed in Table 5 by species in decreasing order of rate of weight loss. All species showed increases in nitrogen during decay but the rates and magnitudes varied by species in the conditions necessary to promote the increases. Among flaccid, fast decomposing plants, proportional nitrogen concentrations increased even under cold, anaerobic conditions when no changes in the proportional nitrogen of the resistant bulrushes were observed. Warm aerated conditions were found to be necessary to promote nitrogen increases in the resistant Scirpus species, and these conditions were so conducive to rapid early decomposition of the softer species that in them particulate nitrogen rapidly increased and then declined. The decline must reflect die-back of microbial populations after the labile substrates in the plant tissue had been utilized. In spite of the fact that all species used in these experi- ments had initial C:N values below or in the range of the "critical C:N" (= 20 to 30) of Parnas (l975), all species apparently utilized inorganic nitrogen available in dissolved form in the media during decomposition. Further, the species with the lowest initial C:N values maintained the highest levels of dissolved nitrogen, and the least resistant species showed the greatest loss of dissolved nitrogen. Aeration at either temperature caused higher dissolved nitrogen con- centrations. This increase was probably the result of greater rates of mineralization of nitrogen during rapid weight loss and is in agreement with the generally declining levels of particulate nitrogen 90 and corresponding increases in particulate C:N ratios during decom- position at 25°C. In summary, among the macrophytes studied, weight loss rates correlated with initial levels of nitrogen in the plant tissue. During rapid decay, the microflora utilized dissolved nitrogen and all tissues showed decreasing C:N values. However, once decay rates slowed, particulate C:N ratios again increased and often so did dissolved nitrogen. Dissolved nitrogen concentrations were probably never limiting to decomposition, and they changed according to environ- mental conditions and rates of tissue decay, not according to low tissue nitrogen content. All species showed similar trends over time in proportional concentrations of nitrogen in particulate and dis- solved form. The temperature and oxygen conditions that were neces- sary for these trends to occur varied with species. The Importance of Decomposition Rates Decomposition is the antagonist to production in ecosystems. Both processes are continually occurring, and the balance between them influences the eventual fate of the ecosystem. Knowledge of the controls of decomposition and of comparative rates will compliment the substantial information that exists on production, providing better understanding of the metabolism of ecosystems. As explained previously, many mathematical approaches have been taken toward explaining rates of decomposition of natural material, mostly plant tissue, in the environment. Most often the simple exponential is used, probably because it is easy to use and adequately fits many observed data; there usually is no biological 91 justification given for its application. Saunders (l972, 1976) has provided a conceptual model which results in an exponential function when converted to mathematical form. His and two other meaningful functions explaining decay rates are compared in Table 6. The essence of Saunders' model (Table 6 [l]) is that weight loss of the substrate over time is a function of the amount of sub- strate present, the concentration of enzymes capable of degrading the substrate, and a constant coefficient accounting for environ- mental constraints on decay rate. On a short term basis, necessary enzymes may be limiting, causing a lag in decomposition of specific compounds until enzyme concentrations increase sufficiently. But, in the entire lake on a seasonal basis the microbes necessary for degradation are present and can increase in a relatively short time to levels promoting decay of the newly available substrates. As Saunders points out, enzyme concentration may be assumed to be con- stant and is included in the decay coefficient. An exponential func- tion results upon integration. A flaw in this model is that the decay coefficient cannot be considered constant. Because tissues are heterogeneous mixtures of interacting components, various fractions of the whole substrate are converted at different rates. Even under constant environmental conditions (usually obtained only in the laboratory) decay rates will be greater in early stages when labile components are being metab- olized and will be lessened as more resistant fractions of the tissue become more concentrated in the residue. It was based on this obser- vation that an exponential function utilizing an exponentially 92 Table 6. Summary of conceptual models used to explain rates of natural decomposition of biological tissues, modified slightly from original forms for comparative purposes. Model* Reference dw - [l] -eE-- -cwE Saunders, l97l [2] g¥-= -a(e'bt)w Present study dw_ " [3] aE-- z -kiw1 Bunnell et al., l977, i=l after Minderman, 1968 * H = proportion of whole tissue remaining t = time E = effective absolute enzyme concentration w1 = proportion of tissue component i remaining k1 = decay constant of tissue component i n = number of components in whole tissue a, b, c = decay constants 93 decreasing decay coefficient was used to describe weight losses in the present study (see earlier discussion of weight loss, Figure 6, Table 6 [2]). The idea of exponentially decreasing decay rates, developed independently in this work, incorporates many of the conclusions of Minderman (l968). In addition, such a model accounts for interactions of individual components, for example, complexation of protein and lignin fractions, in retarding decomposition. The problem with this model involves its further development. The constants a_and b_each represent such a multitude of both environmental and tissue-specific variables that mathematical elaboration of these factors will very quickly make the model too unwieldy to be practical. For this reason, the model of Minderman (1968), as furthered by Bunnell et al. (l977) (Table 6 [3]), though too oversimplified to be acceptable conceptually, is of greatest potential use in decom- position studies. Only as biological information is obtained can realistic decay coefficients, whether they are constants or functions of several variables, be determined and assembled together to make a model which is truly descriptive, and predictive, of the complex processes of natural decomposition. CONCLUSIONS* Fates of Decomposing Organic Matter From the preceding discussions it is apparent that the products of decomposition form a continuum of chemical substances from high molecular weight stable ring structures to short-chain fatty acids to carbon dioxide and other gases. As heterogeneous substrates such as vascular plant tissue decompose, the several individual constitu- ents are differentially subject to microbial attack. Basically, there are four alternative, or sequential, fates for decomposing macrophytic tissue: (a) Complete and efficient decomposition of organic materials to carbon dioxide and water would cause little or no particulate material to remain, and there would not be a large concentration of dissolved organic matter in the media. Less complete decay would involve a smaller loss of particulate plant material and production and accumulation of dissolved organic matter, with rela- tively small amounts of the dissolved organic compounds being oxidized. This pool of dissolved organic matter can be subdivided into (b) relatively refractory high molecular weight compounds and (c) rela- tively labile low molecular weight compounds. Solubility of substrate is crucial for its decomposition. The majority of heterotrophic * Much of the following text is taken from manuscripts cur- rently in press (Godshalk and Wetzel, l977a, l977b). 94 95 utilization of organic matter involves uptake of dissolved materials. The substrate can either be dissolved in water or solubilized enzyma- tically. Vallentyne (l962) has discussed the solubility aspect of decomposition from a biogeochemical point of view. (d) The final possible fate of plant material in lakes is to remain largely undecom- posed; some or nearly all of the plant tissue, depending upon the species and its morphology, may not be converted significantly to any other form and is permanently interred in the sediments. The composite results of this study are summarized in Figure 8. A temperature of 18°C is equidistant between the experimental temperatures of l0°C and 25°C used in the laboratory experiments and therefore is an arbitrary separation of relatively cold and warm conditions. The influence of temperature and oxygen conditions on rates and completeness of degradation are elaborated for the four general fates of organic matter: complete decomposition to carbon dioxide, conversion to refractory or labile DOM, or sedimentation of particulate matter in relatively unaltered form. The lengths of the vectors denote the relative importance of the respective fates under the four general conditions of decomposition. Large amounts of plant tissue are expected to stay in particulate form as a result of cold or anaerobic decomposition. Refractory DOM is produced especially under anaerobic conditions. The most conspicuous features of the results are the direct proportionalities of (a) decomposition of POM to DOM with temperature, and (b) decomposition of DOM to carbon dioxide with oxygen concentration. While both of these findings were anticipated from general knowledge of controls of decomposition of 96 Figure 8. Relative importance, with respect to rates and total accumulation, of the four possible fates of macrophytic tissue observed during decomposition under various conditions of temperature and oxygen concentration. See text for further explanation. (From Godshalk and Wetzel, l977a.) O—mOmm>z> 97 MMWM 002 i 002 v ROOM LDOM ROOM ‘1'. LDOM SEDIMENT SEDIMENT >18%3 ‘ ‘02+*02 + 002 <18C co2 RDOM LDOM ROOM LDOM SEDIMENT SEDIMENT COLD Figure 8 O—mommb 98 organic matter, they have not been evaluated previously for aquatic angiosperms. Decomposition in Lakes Temperature and Oxygen in Lakes The seasonal behavior of oxygen concentrations and tempera- ture with depth in lakes of various productivities is discussed in detail by Wetzel (l975:l26). Temperature and oxygen concentrations at two depths in the pelagial zone of Lawrence Lake (maximum depth l2.5 m) for the year 1975 are diagrammed in Figure 9. Data for the l2 m depth are indicative of environmental conditions at the pelagial sediment-water interface; temperatures at 3 m just above the sediments in the littoral zone were quite close to those measured biweekly in the pelagial zone, but littoral oxygen at this depth was probably less than pelagial concentrations in winter and greater than pelagial concentrations in summer (daylight) conditions (cf. Wetzel, l975:l34). Warm aerobic conditions exist for extended periods of time in temperate lakes only in the pelagial zone during summer. At other locations in the lake where temperatures are relatively high but where water is not subject to continual mixing, absolute oxygen con- centrations, already limited somewhat by lowered solubility at higher temperatures, are likely to be rapidly depleted. Among dense stands of plants in the littoral zone, oxygen consumption, particularly at night, is very high and because of the impeding effect of the plants to water circulation, there is little influx of oxygenated water to these areas. Thus, once initial littoral oxygen supplies are consumed, 99 .compmcmpaxm gmsuga+ Low pxm» mum .Lw>ocgzp Ppmm ucm mcwsam mcwczc mcowpwucou Postmzuomw so mvowgma mmumUwvcw mmmmuam smucmu co mewsupm; mgm>ou mow mo vowgma mmpocmu mmmwuam swan: co mcwgupm: .mmmp .mxmb wucmszmA mo acoN memmpma ms» cw 5 up ucm m we mzpqmu um :mmxxo can mgzumswaswp we cowuznwgpmwo .m wgsmwu 100 m «gnaw; Uwo >02 hUO mum 03¢ .=.=. 23.. ><2 an: ”.52 mm“. 24.. . . o 101 further input of this important oxidant is limited to that produced locally by photosynthesis until the next severe mixing of the epilim- nion. Little is known of the relative redox conditions of littoral waters and sediments in the microzones close to the sediment-water interface or of the effects of seasons, wind, plant density, and photosynthetic activity on littoral oxygen conditions. It is sus- pected that, except in the pelagial zone, warm aerobic decomposition occurs only minimally in temperate lakes, and the faster decomposition initially proceeds under these conditions the sooner oxygen will become limited and anaerobic decay processes will be established. Annual Cycle of Decomposition All combinations of temperature and oxygen simulated in the laboratory experiments of this study are found during one year in the different zones of this typical temperate, dimictic, mesotrophic lake. Decomposition of macrophytic tissue is proceeding under one or more of these situations at all times. How these conditions occur season- ally in a lake like Lawrence Lake, are depicted in Figure lOa-lOf, along with some important aspects of carbon metabolism in the ecosystem. In late summer and early fall (Figure lOa), the growing season for most annual macrophytes ends, and the plants begin to senesce. The actual beginning of decomposition is difficult to define, but certainly some plant parts remain viable while other parts begin to lose their integrity, lose dissolved organic matter (0tsuki and Wetzel, 1974), and begin to be colonized by microflora. If the plants collapse to the sediment-water interface when the water of the littoral zone has not yet greatly cooled and contains high dissolved oxygen Figure lO. 102 General diagrammatic representation of seasonal conditions of carbon metabolism of particulate and dissolved organic carbon of macrophytic origin in a typical temperate, dimictic lake of inter- mediate productivity. See text for explanation. (From Godshalk and Wetzel, l977a.) 103 sewsscem WARM co, MACROPHYTES AEROBIC knee» I PM pom DOM LDOM EPILIMN on WARM Nona-0R0. seomem ANAEROBIC PARTICULATE CROOM LDOMa HYPOLIMNION COLD (a) LATE SUMMER, ANAEROBIC EARLY FALL POM-.DOM / SEDIMENT co, “°°” ""‘ m” COARSE ' AEROBIC COARSE POM COLD O LDOM AEROBIC SEDIMENT ANAEROBIC CR00 LDOMA (b) FALL CIRCULATION WARM ANAEROBIC C02 ER FINE POM “3°”: 2 SE DIME NT (f) SUMMER STRATIFICATION RESIDUAL POM CO \ 2 CO: 7 "NE 9°” WARM ROOM ROOM COARSE P -EROBIC ) AEROBIC ) LDOM SEDI L DOM ".‘V ANAE ROBIC — — — __:-6Co— (E — AEROBI {(510054 . ANAEROBIC (e) LATE SPRING. EARLY SUMMER “WW AEROBIC- ) (c) WINTER ‘N‘ R ‘ ROOM STRATIFICATION ’°”"°°“ (Low) 'oM-ODO LDOM COLD AERO'BIC co2 ) L”! (a) SPRING ’°“ CIRCULATION SEDMN Figure 10 104 concentrations, decomposition will result in the rapid conversion of POM to DOM and of DOM to carbon dioxide. However, in most small temperate lakes the temperature of the water will already be signifi- cantly lowered at this time and, from the results of this study, slow degradation of macrophytic POM can be predicted. Boylen and Brock (l973) studied decomposition processes in lake sediments during winter and observed much reduced glucose uptake rates; the same bacteria isolated at 4°C grew better when the incubation temperature was raised to 25°C. Meanwhile, in the colder hypolimnion of the lake, which commonIy has, at least to some degree, become anoxic from decomposi- tion of organic materials associated with the bottom sediments, an accumulation of DOM has been taking place. Data from deep-water . samples of Lawrence Lake at this time of the year show an increase in absorbance of ultraviolet light and in fluorescence activity, implying an accumulation of refractory dissolved organic compounds of plant origin. Lack of oxygen in the hypolimnetic waters prevents rapid conversion of this DOM to carbon dioxide. It has been shown that DOM from ocean surface waters is relatively easily decomposed, but that from greater depths is quite resistant (Barber, 1968). The age of some resistant deep ocean DOM has been estimated by carbon dating to be 3400 years (Williams et al., 1969). At fall turnover (Figure 10b), mixing of the total lake volume accomplishes two things. First, the entire water body is aerated. which allows the DOM that had been accumulating as a result of anaerobic decomposition to be further oxidized to carbon dioxide and 105 water. Second, recently sedimented POM is resuspended. Particles that had previously been confined to the anaerobic conditions of the sediment-water interface are brought into contact with oxygenated water. While decomposition is slow because of low water temperatures, further conversion of POM to carbon dioxide is made possible. During the cold winter stratification (Figure lOc), decom- position continues both in the water and at the sediments of all depths. Depending on the types and amounts of organic matter present at the sediment-water interface, and the degree of oxygenation accomp- lished by fall circulation, the sediment surface often rapidly becomes anoxic at increasing water depths. Most POM lies at the sediment surface without being appreciably degraded; what decomposition does occur results in the production of DOM with further conversion to carbon dioxide being dependent on available dissolved oxygen. Dis- solved compounds that are produced at the sediment-water interface can escape that stratum by diffusion or in water currents and become part of the pool of potential substrates for many aquatic organisms (Sepers, l977). Spring turnover (Figure lOd) causes aeration of the water mass and resuspension of fine POM from the sediments again. At this time of the year the water is constantly warming and consequently, as long as dissolved oxygen is present, microbial conversion of the DOM which accumulated over winter and of the POM brought up from the sediments will be accelerated and be more complete than under winter conditions. 106 As the epilimnetic waters and littoral sediments begin to warm, more of the heavier, coarser, non-resuspended material may be degraded (Figure lOe). As the rates of decomposition increase because of higher temperatures, oxygen demand increases. By midsummer (Figure 10f), littoral sediments are commonly anaerobic, and complete oxida- tion of organic matter is greatly reduced. DOM is continually gen- erated from macrophytic detritus at these warmer temperatures, and as it diffuses or is flushed to oxygenated waters of the pelagial zone a greater conversion to carbon dioxide can result. The hypolimnion is in large part sealed off physically from oxygen renewal and becomes increasingly anaerobic, allowing an accumulation of DOM that is being degraded at rates less than those of inputs. Effects of the Decomposition Cycle The implications of the variety of conditions under which decomposition occurs in a lake are great. Influxes of readily metabolizable carbon into the system can be largely decomposed in the fall when many macrophytes senesce in the littoral zone, but lower water temperatures in autumn prevent rapid conversion of particulate organic materials to dissolved forms. Constantly low temperatures at the sediment-water interface where particulate matter comes to rest cause this material to be metabolized gradually. Periodic oxygenation of the entire lake allows accumulated labile and, more importantly, refractory dissolved organic matter produced at the sediment-water interface to be converted to carbon dioxide. Resistance to decomposition by refractory compounds displaces carbon metabolism in time. 107 The effect of seasonal mixing is to bring fine particulate material out of conditions of incomplete decomposition for further degradation while suspended periodically in oxic waters. Vallentyne (1962) points out that the influence of gravity "selects" for eventual decomposition of dissolved and particulate materials which are less dense than water by keeping them in or on top of the water column. As long as less dense POM remains suspended it has the potential of being dissolved and therefore the possibility of being acted upon as a microbial substrate. More dense particles eventually sink to the sediments where the liklihood of permanent preservation is higher because of colder and less oxygenated conditions. Many studies have demonstrated the importance of particle size to decomposition. In most cases decomposition of smaller particles is faster than that of larger particles. As particle size decreases, rate of weight loss, oxygen consumption, and numbers of microbes per unit weight of detritus all increase (0dum and de la Cruz, l967; Fenchel, 1970; Gosselink and Kirby, l974; Hargrave, 1972). During the course of decomposition of macrophyte tissue to DOM and/or carbon dioxide, the size of the macrophyte fragments will decrease. As particle size decreases, the surface area:volume ratio increases, providing greater area for microbial attack. At the same time, as the more labile constituents of the particles are utilized, the residual material becomes proportionately more resistant to further decay. These two processes have opposite effects on overall decom- position rates. In addition, the production of large amounts of fine particles may affect subsequent decomposition rates as the fine 108 particles will compact more densely, thus limiting diffusion of oxygen and waste products and thereby causing more severe reducing conditions (cf. Acharya, l935). Coarse, heavy particles are not resuspended and are not removed from the littoral zone where they are more effectively decomposed under warmer and more frequently oxygenated conditions. This provides that only the most refractory particulate organic materials will be permanently buried in the sediments of the basin. The extent of transport of particulate material of littoral origin to other regions of a lake is unknown. Thus, the metabolism of the large amounts of carbon that become available as senescent macrophytic tissue in the fall is delayed by intermittent decomposition of POM to DOM, and the conver- sion of this DOM to carbon dioxide is further buffered through time. Pulsed decomposition provides stable levels of continual carbon metabolism. Response of Decomposition to Eutrophication The most common perturbation to natural lacustrine ecosystems is eutrophication, the acceleration of nutrient input. The response of major groups of primary producers in lakes of increased fertility is explained in detail elsewhere (Wetzel and Hough, 1973; Wetzel, l975:4l6). Present data on decay of plant tissue allow general pre- dictions to be made regarding the response of decomposition in such systems to increased inputs of detrital carbon. Increased bacterial activity in response to higher concentra- tions of substrates can be expected immediately. In a comparison of 109 seven lakes of varying trophic state, Godlewska-Lipowa (l975) found increased bacterial numbers, biomass, and oxygen consumption in more eutrophic lakes. The oxygen consumption of lake water samples to which additional organic substrates were added, compared to controls without added substrate, was greater in samples from more eutrophic lakes, an indication of higher gross decomposition rates. However, this relationship does not mean that increased respiration will balance the increased photosynthesis. The amount of material that sediments to the bottom of the lake and becomes less likely to be decomposed increases as the amount of carbon available for decomposi- tion increases and as mean lake depth, or mixed-layer depth, decreases (Ohle, 1956; Hargrave, 1975). Hence, as primary production increases, absolute rates of decomposition also will increase, but efficiency of decomposition (i.e. decomposition/production) will decrease and accumulation of organic matter will be accelerated. Increased loading of sediments generally will increase the rate at which reducing redox conditions are establsihed, and the effect that this has on regeneration of nutrients has already been mentioned. Mixed-layer depth is important in this regard also and Olah (1975) has described the function of the metalimnion in isolating sources of nutrients, particularly phosphorus, from oxidation-induced chemical precipitation and promoting "self-accelerated eutrophication." The presence of organic carbon in the sediments does not necessarily imply strong reducing conditions or high oxygen consump- tion. The quality of that carbon, i.e. whether it is susceptible or resistant to microbial degradation controls the demand for oxidants. 110 In deeper oligotrophic systems (oceans, huge lakes) sedimented carbon is predominantly resistant and reducing conditions are weak, but in shallower, more productive systems (coastal waters, eutrophic lakes) more labile carbon reaches the sediments and oxidation demands are greater (cf. Rybak, l969; Pamatmat, l973; Bordovskiy, l974). Sedimentation of undecomposed biological material in lakes has long term effects on the filling of the basin. As emergent macrophytes dominate primary production in increasingly eutrophic situations, there will be a corresponding increased loading of the littoral sediments with greater amounts of tissue. Also, the tissue from these rigid, erect plants which contain greater amounts of structural tissue will be more resistant. Accumulating organic matter may cause filling of the basin by encroachment of the littoral zone toward the center of the lake. How fast this process occurs depends on the morphometry of the basin and where sediments accumu- late most rapidly (Lehman, l975). Comparison of sediment character- istics at different depths in shallow ponds has demonstrated that inorganic, and presumably organic, average particle size decreases at greater depths, probably as a result of the sieving effect of resuspension and subsequent settling of fine-grained materials (Boyd, l976). This finding lends support to the idea of coarser, bulkier pieces of macrophyte tissue remaining in the littoral. Increased littoral zone productivity in a hypereutrophic situation has been implicated as a cause for the very rapid extinction of the lake (Manny et al., 1977). SUMMARY The decomposition of aquatic macrophytes of the littoral zone is an important part of the total metabolism of carbon in a lake, especially in small lakes where littoral production is of similar or greater magnitude than pelagial planktonic production. Temperature and oxygen concentration are two environmental parameters that were found to strongly influence aspects of decom- position. Temperature primarily affected the rate of conversion of particulate tissue to dissolved organic matter. If oxygen was present, the dissolved detrital carbon was metabolized to carbon dioxide and water, but DOM accumulated, at least initially, under anaerobic con- ditions. The floating-leaved plant decomposed faster than sgpmersed P19!E§;#Whjch decomposed_faster than the emergept_plant, Decaykratgs were related to_in1tial tissue nitppgepfland fibergppptgpts, with high-nitrogen, low-fiber plants decomposing more rapidly than plants I with low initial nitrogen and high fiber. Under environmental con- xx} ditions more conducive to decomposition (i.e. warmer and more oxygen), resistance to decay was at least partially overcome. Hence, all species showed similar trends in decomposition, but the species were different in the conditions of temperature and oxygen that were required to promote those trends. 111 112 One class of products of decomposition is resistant organic compounds. These compounds are derived mostly from phenolic and lig- nin plant constituents. One of their roles in the aquatic ecosystem is as carbon substrates which are not readily assimilable by bacteria. The delayed metabolism of these energy sources represents a buffer- ing of the input of detrital organic matter to the lake ecosystem. 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Specific figures in the pages following the indices are referenced by the tabulated Appendix Figure numbers. 128 GUIDE TO APPENDIX TABLES Parameter ATP ........................ Carbohydrates (TNC), percent of initial content . . . . Carbohydrates (TNC), percent of recovered weight Carbon, dissolved organic (DOC) .......... Carbonznitrogen ratio, dissolved ......... Carbonznitrogen ratio, particulate ........ Carbon, total dissolved .............. Carbon, total particulate ............. Cellulose, percent of initial content ....... Cellulose, percent of recovered weight ...... Eh (Redox potential) ............... ETS ........................ Fluorescence ................... Hemicellulose, percent of initial content ..... Hemicellulose, percent of recovered weight . . . . Lignin, percent of initial content ........ Lignin, percent of recovered weight ........ Nitrogen, total dissolved ............. Nitrogen, total particulate ............ pH ........................ UV absorbance ................... Weight remaining ................. 129 Table H F G Page 137 135 136 131 139 138 139 138 135 136 130 137 133 135 136 135 136 139 138 130 132 134 vN wN NN ~N ON 0 MN .0~A0h04 o— mu 0 mu .0~A0hoa:¢ h— 0_ m~ fig n— U nN .o~40hoana10alo~A0ho¢ Nu —_ O~ 9 Q O on .o—nouod h o U 0— .oonuoan¢ nu Nu m ¢ 0 N u 0 Cu .o~46hoa:a10ulouaouo< Bauawomha> E:~_>390ho~oa mm~mxo~u aumafiuah0anflm usafioa haaaaz Sam—kfiaowhbz muaaz m5Ah~om msmhaom mac—Pmnzoo A um GOG .mhonfidz ohnwmh Hmvloma< no Novflm .m o—Aflb vanoamd 132 Nb —5 ON ow we 0 mN .ounouo< no 00 U nN .o~aouoafl< no #0 no No _o O nN .0~A0hoa:a10ulo«Aouo< 60 on On hm on U 0— .o~aouo< mm ¢m 0 O— .omaohoand mm Nm um Om ow o o— .O~A0hoa=o10ulomaoho< Eauamomhab E:—~b£&ouo~o£ cumulo—u mm—aumEAOuaum mausoa hanaaz E=~—>£Aomh>2 mafia: manhuom azahmom mzcuhmnzco A RA comaAhomaa >D .nhonaaz chammm Havfloaad no Nova“ .0 omaah Nuvnoam< 00 mo +@ no No 0 nN .o~nono< _o 00 0 MN .omA6hoa:< on we pm on mm 0 mN .om40hoafla10ulo~A0ho< ¢w mm Na #6 ON 0 On .o~40ho< on wk 0 o— .ouaouoand was .2. on mu 3.. 2. o 2 622251313 cocoa EdaomouuNP 8:—~>£AOA090£ mmuflwo—u mm—aflmahouaum Quezon haaasz Bu->fiaouhhz maaaz manhuow usnhmom mac—P_on0 A490hou04 .iiwmmwuo4u 04—an48h0445n .muufloRI. Lanna: Esmuhfinomhh: oaaaz manhuom mighuom mzc~B~ono 4 85445490ho~04 0444No—u OmnaflmahOunfiu auuaoa haflnaz Bun—54A04hhz aaanz uflAhuom Isahuom mzcnhnnzcu 4§Fzmznmmmxfl .uuHOHOQBoo Aoamu and IOthVhAOAhao no «floufloo ~04-fl4 «o anachom .Iuonflnz Ohflhmh N4VI0AQ< no Iowan .h 0441? I—vfloand 136 ONN NNN ONN mNN ONN head"! .4uh04u—4 .4 Hoonhuo~n43 ONN NNN 4NN ONN o—N Leann? .uauuanon .4 033.4304 O—N h—N O—N w—N v—N young? .4ah0444— .4 conch3m4 O4N N4N 44N OnN oON hofiaau .uau0444— .4 oouoh304 OON NON OON mON «ON 0 ON .o~40uo< NON NON 0 ON .o—aohoa=< ~ON OON oo— O04 pom O mN .044050ana10410440u04 OO— mo— #04 mo— N04 0 O— .0440ho< 404 Oo— 0 O4 .omaohoa=< 0&4 OO~ NO. 00— mO— O O— .omaohoanalo~10440ho< EnuaM04ua> 854—hdaououon @4—4N04u 344au48h044ul mauaoa ha4auz 354—bflnomaiz uaaaz nunhmom manhmom mZO~F~OZOU 4490h0u04 hummuo—u au—ud48A04460 oflafloa hfl4a=z Eng—kfinouhht unwaz udahmom ulnhmom QZO~F_OZOO 4 Bfl~—>4Oopouoa nmumxo~u 044afl48h04450 nuance nuanaz Eun~>4ao~hhz manna muahuow uaaauom OZOuhunZOO 4 8 1.0: I I I I l 0 10 25 SO 90 180 DAYS OF DECOMPOSITION : :pH o—————0Eh Appendix Figure 7. Decou oi Myriophyllum heterophyllum in loboroioru under onoerobic conditions oi 10°C. pH and Eh (millivolis) oi medio. <> <> ——0 m L 4 <3 / - ID 3 -N OOOOOOOOOOOOOOOOOOOOOOO 00000000....OOOOOOOOOOOOOOOOOOOOO.o c> 10 cu Io- ., c: c> In [D I I I I ‘I O 10 25 SO 90 180 DAYS OF DECOMPOSITION O :pH ‘fi th Appendix Figure 8. Decou oi Scirpus acutus in loboroiorg under aerobic condiiions oi 10°C. DH and Eh (millivolis) oi medio. Eh Eh 500 QC ”fig-u“ __________._ ——-—-—o L _—. 8 a: 4. nu 2El\a. ........................................................... no 0 a (D- D. O 0 ID ID I I I I | O 10 25 50 90 180 DQYS OF DECOMPOSITION Appendix Figure 9. Decou oi Scirpus subterminalis in Ioboroioru under oerobic condiiions oi 10°C. pH and Eh (millivolis) oi medio. O O in 0 1.0 'N E b.- ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo po 0 1.0 N m. . I O 0 ID ID i I I I l 0 10 25 50 90 180 DRYS OF DECOMPOSITION : :pH 0— — ——0Eh Appendix Figure 10. Deoou oi Nojos flexilis in Ioboroioru under aerobic condiiions oi 10°C. pH and Eh (millivolis) oi medio. Eh Eh 500 O a) y/D\\ 43 E 5" ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo .0 0 ID (0' J? O 53 ID I I f I I 0 10 25 50 90 180 DRYS 0F DECOMPOSITION Appendix Figure 11. Decou oi Myriophyllum heterophyllum in loboroiorg under aerobic condiiions oi 10°C. DH and Eh (millivolis) oi medio. 500 250 'O 0 II) N ‘0- D. O 0 ID ID I I I I 0 10 25 180 5'0 so onvs OF DECOMPOSITION : w‘pH % cEh Appendix Figure 12. Decou oi Nuphar variegatum in loboroioru under oerobic condiiions oi 10°C. DH and Eh (millivolis) oi medio. Eh Eh 500 O 1.0 I'I'M 00.000000000000000.00.000000; ccccccccccccccccccccccccc $4.051 —# - _._——-" v. VN—‘MM 8 (0" “1' o 0 ID ID I I I I I 0 IO 25 $0 90 180 DRYS OF DECOMPOSITION : :pH O :Eh Appendix Figure 13. Decoy oi Scirpus acutus in loboroioru under oerobic-io-onoerobic condiiions oi 25°C. pH and Eh (millivolis) oi medio. 500 250 0 :5 IO N (0' D. O 0 ID ID I I I I I 0 10 25 50 90 180 DRYS 0F DECOMPOSITION : :pH 5 fiEh Appendix Figure 14. Decog oi Scirpus subterminalis in Ioboroiorg under oerobic-io-onoerobic condiiions oi 25°C. DH and Eh (millivolis) oi medio. 500 250 0113 0 ID N I o 8 IDI I I I I 0 10 25 50 90 180 DRYS OF DECOMPOSITION Appendix Figure 15. Decou oi Najas flexilis in Ioboroiorg under oerobic-io-onoerobic condiiions oi 25°C. DH and Eh (millivolis) oi medio. 500 250 0 If! 0 U) m m. I | O 0 ID ID I I fi I I 0 10 25 50 90 180 DRYS OF DECOMPOSITION ; fipH 5 :Eh Appendix Figure 16. Decou oi Myriophyllum heterophyllum in loboroiorg under oerobic-io-onoerobio condiiions oi 25°C. DH and Eh (millivolis) oi medio. 500 250 O -250 -SOO o 10 23 so so oan OF DECOMPOSITION r :pH ? :Eh Appendix Figure 17. Decoy oi Nuphar voriegoium 180 Eh in loboroioru under oerobic-io-onoerobic condiiions oi 25°C. DH and Eh (millivolis) oi medio. 500 250 ”O 0 ID N m. D. O 0 ID ID I I I I I 0 10 25 180 50 90 DQYS OF DECOMPOSITION : :pH : flEh Appendix Figure 18. Decog oi Scirpus subterminalis in Ioboroiorg under onoerobic condiiions oi 25°C. DH and Eh (millivolis) oi medio. Eh $00 250 c: c: A (9' .. <> . 8 ID I I j I I 0 10 25 50 90 180 DAYS OF DECOMPOSITION Appendix Figure 19. Decog oi Myriophyllum heterophyllum in Ioboroioru under anaerobic condiiions oi 25°C. DH and Eh (millivolis) oi medio. c: c: a) _. _-—o— -— —— —— ——.. ___.m Ii5¢:::::::”‘_TT=::-~44_E —TT 1" c> ID or nu E 5.! ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo .0 c: 8 ‘DJ PI c: c: 10 ID I I I I O 10 25 180 5'0 so DRYS 0F DECOMPOSITION : :pH : :Eh Appendix Figure 20. Decoy oi Scirpus acutus in Ioboroioru under oerobic condiiions oi 25°C. DH and Eh (millivolis) oi medio. Eh Eh $00 03* __...- —_ _:_. ._.._.. z: -: / 8 or flu E “I! 00000000000000000000000000000000000000000000000000000000000 .o c: 8 (0' ., c> 8 ID I r I I ‘l 0 10 25 SO 90 180 DAYS OF DECOMPOSITION Appendix Figure 21. Decog oi Scirpus subterminalis in loboroiorg under oerobic condiiions oi 25°C. pH and Eh (millivolis) oi medio. c> c> ID C) In «I g but ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo .0 C) In n1 (0' ., c: c> ID ID I I I I I I 0 10 25 SO 90 180 DAYS OF DECOMPOSITION ; :pH ‘fi :Eh Appendix Figure 22. Decoy oi Nojos ilexilis in loboroiorg under aerobic condiiions oi 25°C. pH and Eh (millivolis) oi medio. Eh Eh 500 m - L 4"— - —- +- r / 0 ID N 'N E “I! o ooooooooooooooooooooooooooooooooooooooooooooooooooooooooo .o 53 “,1 .0 O 0 ID ID I I I I 0 10 25 50 90 180 DRYS 0F DECOMPOSITION ; :pH T :Eh Appendix Figure 23. Decoy oi Myriophyllum heterophyllum in Ioboroioru under oerobic condiiions oi 25°C. DH and Eh (millivolis) oi medio. O O a) __ - run T _ — O V/ 0 ID Q 'N E h. P D O OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO .0 0 ID N (0" ’ I O 0 ID ID I F I I 0 10 25 50 90 180 DAYS OF DECOMPOSITION 5 :pH : :Eh Appendix Figure 24. Decou oi Nuphar variegatum in loboroiorg under oerobic condiiions oi 25°C. DH and Eh (millivolis) oi medio. Eh Eh 150 200 DOC OI I I I I O 10 25 50 90 ISO DQYS OF DECOMPOSITION ; :03 .._ — —-PM30 °- -- -°PM10 - - — — — -UM2 -----------UMOS Appendix Figure 25. Decog ai Scirpus acutus in laboraiorg under oerobic-io-anaerobic condiiions oi 10°C. Dissolved organic carbon (mg/I/g iniiial AFDW) in various molecular ueighi irociions oi DOM. 200 OI—l I '— 0 10 25 50 90 180 DQYS OF DECOMPOSITION ; :03 ; :PM30 ~—- -—— ——~PM10 — — — - — -UM2 - --------- -UMOS Appendix Figure 26. Decou oi Scirpus subterminalis in laboroioru under oerobic-io-onaerabic condiiions oi 10°C. Dissolved organic carbon (mg/I/g iniiial AFDW) in various molecular ueighi iraciions oi DOM. 0 EL 0 235% O o. m --.._.-"‘-': CT I I I I 0 IO 25 50 90 180 DQYS OF DECOMPOSITION = <63 -— — -—oPM30 — -— —-oPM10 - - — - — «0M2 - --------- ounos Appendix Figure 27. Decau oi Najas flexilis in laboroioru under oerobic-io-onoerobic condiiions oi 10°C. Dissolved organic carbon (mg/I/g iniiial AFDW) in various molecular ueighi iraciions oi DOM. ZOO 150 . DOC 0 1'0 2'5 so so 180 onvs 0F DECOMPOSITION -— - - - — «UMP. - --------- ouMos Appendix Figure 28. Decou oi Myriophyllum heterophyllum in lobaroiorg under oerobic-io-anoerobic condiiions oi 10°C. Dissolved organic carbon (mg/l/g iniiial AFDN) in various molecular ueighi iraciions oi DOM. 200 DOC O I I I I I 0 10 25 50 90 180 DRYS OF DECOMPOSITION .4 :93 .__. —— ——-PM30 — -- -—°Pm° -— - - — — oune - --------- -UM05 Appendix Figure 29. Decau oi Nuphar variegatum in laboroioru under oerobic-io-onoerobic condiiions oi 10°C. Dissolved organic carbon (mg/l/g iniiial AFDW) in various molecular ueighi iraciions oi DOM. 800 DOC 50 90 DAYS OF DECOMPOSITION 2 :os .__ —— —-PM30 .__ -—- -—-PM10 ._ — — - — ~UM2 - --------- «OM05 Appendix Figure 30. Decoy oi Scirpus subterminalis in laboraioru under anaerobic condiiions oi 10°C. Dissolved organic carbon (mg/i/g iniiial AFDW) in various molecular ueighi iraciions oi DOM. 200 ISO DOC O I I I 0 IO 25 5 90 ISO DDYS OF DECOMPOSITION : ‘ :08 o— — —0PM3O = =PMIO ._ — -— — — -UM2 - --------- -UMos Appendix Figure 31. Decag oi Myriophyllum heterophyllum in laboraioru under anaerobic condiiions oi 10°C. Dissolved organic carbon (mg/I/g iniiial AFDH) in various molecular ueighi iraciions oi DOM. 200 DOC 50 90 DQYS OF DECOMPOSITION :- - - - — «0M2 - --------- «UMos Appendix Figure 32. Decag oi Scirpus acutus in laboroioru under aerobic condiiions ai 10°C. Dissolved organic carbon (mg/i/g iniiial AFDW) in various molecular ueighi iraciions oi DOM. 200 c: m. F. c: 8 3- c: c: 10 c: 0 10 25 50 90 180 DAYS OF DECOMPOSITION , :03 ~—— — —oPM30 °-— — —'°P|‘I10 - — — — — «0M2 - --------- «UMos Appendix Figure 33. Decou oi Scirpus subterminalis in laboraioru under aerobic condiiions oi 10°C. Dissolved organic carbon (mg/l/g iniiial AFDW) in various molecular ueighi iraciions oi DOM. O O N 0 EL 0 8 S- O O m- “‘4 \ £?-»——.m;:::;;::; _ O I I 0 10 25 50 90 180 DQYS OF DECOMPOSITION , :93 ~———-———--—~PM30 -- -—- -—*PM1° '- — — — — ‘UME " --------- °UM05 Appendix Figure 34. Decou oi Najas flexilis in laboraioru under aerobic condiiions oi 10°C. Dissolved organic carbon (mg/I/g iniiial AFDW) in various molecular ueighi iraciions oi DOM. 200 150 DOC 100 50 O u 0 10 2'5 so so 180 DAYS OF DECOMPOSITION ~ :65 -— -— —-PMso ._ — -—-PMIo - — — — - «UM2 - --------- «UMos Appendix Figure 35. Decau oi Myriophyllum heterophyllum in laboroioru under aerobic condiiions oi C. Dissolved organic carbon (mg/i/g iniiial AFDW) in various molecular ueighi iraciions oi DOM. 200 50 90 DAYS OF DECOMPOSITION ‘ -£GS -—- ----*PM30 -— -—- -—~PM10 ... _ — — -— .UMZ 0- -------- ‘UMOS Appendix Figure 36. Decou oi Nuphar variegatum in laboraiorg under aerobic condiiions ai 10°C. Dissolved organic carbon (mg/I/g iniiial AFDN) in various molecular ueighi iraciions oi DOM. 200 DOC O I I I U O 10 25 50 90 130 DQYS OF DECOMPOSITION .— _. _ — —- oUMB 0' --------- "UMOS Qppendix Figure 37. Decou oi Scirpus acutus in laboraiaru under aerabic-io-onoerobic condiiions 01 25°C. Dissolved organic carbon (mg/O/g initial QFDN) in various molecular weight iraciions oi DOM. 200 1:50 DOC 50 90 DRYS OF DECOMPOSITION i :03 ; :PM30 ~—- -—- -—~PM10 :- — — — — ‘UM2 .. --------- «UMOS appendix Figure 38. Decay oi Scirpus subterminalis in laboratory under aerobic-io-anoerobic condi1ions 01 25°C. Dissolved organic carbon (mg/o/g iniiial RFDN) in various molecular weight iraciions oi DOM. 200 DOC SO 90 DAYS OF DECOMPOSITION - :03 ~——--——— -—~PM30 ~—- -- -*PM10 :- — — - - «UM2 .. --------- oUMos Appendix Figure 39. Decag oi Najas ilexilis in loboratorg under oerobic-io-onoerobic conditions at 25°C. Dissolved organic carbon (mg/o/g iniiial AFDN) in various molecular ueighi iraciions oi DOM. 100 1 50 200 DOC 50 O I I I I ' --:}4 0 10 25 50 90 180 DAYS OF DECOMPOSITION Afi :GS : 3PM30 ‘—‘ — —‘PM10 ._ _ _. _ _ .una .. --------- oUMOS Appendix Figure 40. Decou oi Myriophyllum heterophyllum in laboroioru under oerobic-io-onoerobic conditions at 25°C. Dissolved organic carbon (mg/I/g iniiial AFDN) in various molecular weight iraciions oi DOM. 50 90 DAYS OF DECOMPOSITION - =03 o-———-oPM30 — —- —~Pmo Z. _ ._ _ _ «UM2 .. --------- oUMOS Appendix Figure 41. Decau oi Nuphar variegatum in laboratoru under oerobic-io-anaerobic conditions at 25°C. Dissolved organic carbon (mg/i/g iniiial AFDN) in various molecular weight iraciions oi DOM. 200 150 DOC 50 90 DQYS OF DECOMPOSITION : :GS : =PM30 ’— — —°PM10 - - - — - iUME - --------- «umos Appendix Figure 42. Decou oi Scirpus subterminalis in laboraioru under anaerobic conditions at 25°C. Dissolved organic carbon (mg/D/g iniiial AFDH) in various molecular weight iraciions oi DOM. 200 DOC ~ :08 -— — -—-PM30 ._ — ——-PMIo ._ — — - — «uma ~ --------- oUMos Appendix Figure 43. Decag oi Myriophyllum heterophyllum in laboraiorg under anaerobic conditions at 25°C. Dissolved organic carbon (mg/o/g iniiial AFDN) in various molecular weight iraciions oi DOM. O o N O a. O 8 9.- O O mq c’o 10 25 so 180 onvs OF DECOMPOSITION - :GS .__ — —0PM3O ._ — —-Pmo ._ — — - — oume ~ --------- oumos Appendix Figure 44. Decay oi Scirpus acutus in laboraiorg under aerobic condiiions at 25°C. Dissolved organic carbon (mg/O/g iniiial AFDN) in various molecular ueighi iraciions oi DOM. 200 0 EL 0 8 2- o O m. c>£%-‘ - 45:4T7:F:==:-3::eiéi..:::—n::;.——~—n;:..;;}é 0 IO 25 50 90 180 DAYS OF DECOMPOSITION " " _ — - ‘UM‘? * --------- «UMos Appendix Figure 45. Decou oi Scirpus subterminalis in laboratoru under aerobic conditions at 25°C. Dissolved organic carbon (mg/O/g initial AFDN) in various molecular weight iractions oi DOM. O O N 0 EL 0 8 S- O 0 ml m -- ._ ' nfi—-a-._-v. nun--fi.&-.='._---u ‘ o . . -. -_ ,- 0 IO 25 50 90 180 DAYS OF DECOMPOSITION -- — — - - oUM2 o- --------- .umos Appendix Figure 46. Decau oi Najas ilexilis in laboratoru under aerobic conditions at 25°C. Dissolved organic carbon (mg/i/g initial AFDN) in various molecular weight iractions oi DOM. 200 150 DOC O o 10 25 so so 180 DAYS OF DECOMPOSITION - :68 ~—— — —-°PM30 — — —-PM10 —- — — — — «UM2 ~ --------- «OM05 Appendix Figure 47. Decau oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 25°C. Dissolved organic carbon (mg/i/g initial AFDN) in various molecular weight iractions oi DOM. c: c: as C) EL c> 8 2- c: c> mi 0 0 10 25 50 90 180 DAYS OF DECOMPOSITION :7 :GS ~___.___.;_~pM30 ~—- -—— -—~PM10 .- _ — — — «UMB 0- --------- ‘UMOS Appendix Figure 48. Decau oi Nuphar variegatum in laboratoru under aerobic condiiions at 25°C. Dissolved organic carbon (mg/i/g initial AFDN) in various molecular weight iractions oi DOM. o_.4 o.s j UV ABSORBANCE 0.2 0. c5- _____. ..._... <3 <3 5 90 DAYS OF DECOMPOSITION : :93 s~ :PM3O -- -- -—*PM1° - — — — - oUM2 .. --------- oumos Appendix Figure 49. Decay oi Scirpus acutus in laboratory under aerobic-to-onaerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. “3 O “I o. w ‘2’“! S c- (K I, nun-fl” 8 # u—I"""' m of" /. c: «I” ,,. - / / S a-r’ / / o— —— _. ____. / hnfinnnnnnnfissnznz—Sn—o so so 180 DAYS OF DECOMPOSITION ‘ 403 ? :PMSO *—- -- -*PM10 :- — - — -- oUMa .. --------- «UMos Appendix Figure 50. Decay oi Scirpus subterminalis in laboratory under aerobic-to-onaerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial nFDN. “3 O V 64 I.” .‘z’ "2 S 0. Di 8 0a g O ‘/ > D '1 - T s ‘2 -e--_~--_.=--:::--:::-:-':-':-"‘-:'-:'-':-:'-:'-=-=-=:3 O I I I I I 0 IO 25 50 90 180 DAYS OF DECOMPOSITION -— — — — — «UM2 ~ --------- .uMos Appendix Figure 51. Decoy oi Najas ilexilis in laboratory under oerobic-to-anaerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. "3 O “I o. "J ‘2’ "a EEC» 05 8 a: 8 o // > _. _____ ___...... ._——-—v o :>'3 __1:;r_=h’___‘__=g:__:_- -__ -_- ._~ 0 0" O -:..-:..-=..-.=..-I:MJII—-I—-I-‘=“-3-‘5-1-"3 <5 ' . ' 0 9° 180 DAYS OF DECOMPOSITION - :63 % fi-mulgo __ _ —"*PM10 ;- - — — — .uMa ~ --------- oUMos Appendix Figure 52. Decay oi Myriophyllum heterophyllum in laboratory under oerobic-to-anoerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. “2 c: ‘E 0‘ ul 3"! So- m fl: 8“: Egc> s .. _:..:" O. «o O -—.————=-*-"”—-P.‘ c> O 90 180 DAYS OF DECOMPOSITION s :08 — —— -—oPM30 ._ —- ——~PM10 .- _ _ — — OUME 0- ------- ’UMOS Appendix Figure 53. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. “3 O “I 0. LI] 3 "Z S o- m 8 a: >. "" ° 3 '2' O ‘3 O I I I I 0 IO 25 50 90 180 DAYS OF DECOMPOSITION : :GS : 4PM30 *— — —‘PMIO ._ — - — - «UM2 ~ --------- oUMos Appendix Figure 54. Decoy oi Scirpus subterminalis in laboratory under anaerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. "3 c> “I o- u: 3“! So- :2 530: a: . Co. /o—~_._____-_—_ >' \\\ - ‘-’,,’ '“‘:;=a DH fi#/ fr ; —"-"'_—f_ __ _ fl 5 \ ..... .... ,- I.. _,_...._ a ‘3 ,, '~~—~—~*-4=4=-:L::::;:::.:;::::J:.. .......... . O I I I T" O 10 25 50 90 180 DAYS OF DECOMPOSITION if #433 r— spnao ~—- -—— -—~PM10 --——-——«UM2 ~ --------- ‘UMos Appendix Figure 85. Decay ai Myriophyllum heterophyllum in laboratory under anaerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per g initial AFDN. 9.4 0.5 3 UV ABSORBANCE 0. 0 ~ . I. O 10 25 50 90 180 DAYS OF DECOMPOSITION : 44:68 = ssPMBO *—- -- -—*PM10 - — — - — ~UM2 - --------- «UMos Appendix Figure 56. Decay oi Scirpus acutus in laboratory under aerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. "i O V 64 I.” ‘2’ “2 s o- m _.___A EEC? - En“ 0' -. > o 7" "I 0 °. 0 '1 ’ ' ’ T- I 0 10 25 50 90 180 DAYS OF DECOMPOSITION P =GS = =PM30 ~—- -—— -—*PM10 ._ — — — -— «UMa ~ --------- oUMos Appendix Figure 57. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. 0.4 0.5 UV ABSORBANCE o 10 as So so 180 DAYS OF DECOMPOSITION = =68 = =Pr-13O -— — -——~PM10 - — — — — «ume .. --------- «Umos Appendix Figure 58. Decoy oi Najas ilexilis in laboratory under aerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per g initial AFDH. UV ABSORBANCE 0.0 0.1 50 90 DAYS OF DECOMPOSITION L :63 : =PM30 ‘—"’ _ "—‘PM10 l- — — — — iUM2 ~ --------- oUMos Appendix Figure 59. Decay oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per g initial AFDN. "2 or V. 0 LI] 2 “3 SE 0 ’ O! 8 a: Ego' \\ > \ :"I \\ °“-.~ I __s o / "—-——__ q ___......-—-—---=-— -. O \‘e‘f'fiea-‘s—V-t-='-':'-.'_'-T.'1‘:-T- ~~~~~~~~~ 0 O I I r I I TTTTTT T’- O 10 25 50 90 180 DAYS OF DECOMPOSITION : :93 : :PM30 -- -—- -*PN10 "' '- — - — 4'UME? 0- --------- ‘UMOS Appendix Figure 60. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 10°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per g initial AFDN. 0.4 0.5 .3 UV ABSORBANCE O o I I‘ 0 IO 25 50 90 180 DAYS OF DECOMPOSITION F’ :63 =‘ =PM30 0—— -' -—*PMIO ~— — — — — «UMP. ~ --------- .uMos Appendix Figure 61. Decay oi Scirpus acutus in laboratory under aerobic-to-anaerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per g initial AFDH. "f C) __.s. ‘E 0. ll] fz’ “2 E§Ci O! 8 a: g§c> >. 3 '1 O 0. h"-¢£---*n__--.._-_~.?-8‘:_‘='-'=.'—'—'P—v—-—*Pu-t—-«-~——--~-O c) I ' ' W -m 0 IO 25 50 30 180 DAYS OF DECOMPOSITION : :GS 0—— —- —°PM30 “'— — ——‘PM10 .- _ — — — OUME 0- ------- ‘UMOS Appendix Figure 62. Decay oi Scirpus subterminalis in laboratory under aerobic—to~anaerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDH. "2 c: v 64 u: E’ "3 s o- I: c: a) a: a: >~ :> 50 90 DAYS OF DECOMPOSITION : secs : :PMSO ~—- -—— ——~PM10 - — — — — oUM2 - --------- «UMOS Appendix Figure 63. Decay oi Najas ilexilis in laboratory under aerobic-to-anaerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. "2 (3, ‘E c> u: ‘z’ "2 g§c> a: 8 a: g§c> >, -'-" ".' c> ‘2 01 I I I O 10 25 50 180 DAYS OF DECOMPOSITION : :GS ~———-———--—~PM30 ~—- ~—— -—~PM10 - -— — - — -UM2 ~ --------- iUMOS Appendix Figure 64. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. UV ABSORBANCE 0 1b as so so ISO DAYS OF DECOMPOSITION .9 :03 .9 :Pmso —— — ——-PMlO «— — — — - «UM2 - --------- «umos Appendix Figure 65. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per g initial AFDN. "3 O ‘5 o. LIJ 0 2 CI: m (K o (D a: CI: > D "I 0 °. 0 I I I I I O 10 25 50 90 180 DAYS OF DECOMPOSITION ._ - — — — .UMe .. --------- oUMos Appendix Figure 66. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. 0.2 0.3 0.4 0.5 UV ABSORBANCE 0.0 0.1 0 1'0 2'5 5'0 so 180 DAYS OF DECOMPOSITION : =68 ._ — ——-PM30 -— — ——-PMIO ._ - — - - *UM2 ~ --------- oUMos Appendix Figure 67. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per g initial AFDN. 0.4 0.5 UV ABSORBANCE <3 0 10 25 50 90 180 DAYS OF DECOMPOSITION : :33 : :PMBO *- -- -—*PM1° - — — - — «UM2 ~ --------- «UMos Appendix Figure 68. Decay oi Scirpus acutus in laboratory under aerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDH. "3 O “I 0‘ N I.“ / / x x ‘5 ‘2) m f... .— "‘""' .‘\ x “a Cl: .I / \- x O! K g 8“: // o:€” > // :pwq c5 :6’! o. . a—Oc—u —— _. — — o .- -"'-.- -"'-"°'..--'—.--'~=t--- - --._ — - — 0 10 25 50 90 180 DAYS OF DECOMPOSITION - — — - —- «uM2 - --------- oUMos - Appendix Figure 69. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. ”3 O V dd I.” 3 "2 s o- m 8 a: 3 o‘ > D "I o q o ' ' W O 10 25 50 90 180 DAYS OF DECOMPOSITION - - — — - «UMe - --------- «OM05 Appendix Figure 70. Decay oi Najas ilexilis in laboratory under aerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. 0.4 0.5 UJ £3“? So- “ a... 80 > A 3,: N. __ __ _VM_. 0 0. ch-=::-——-.----.:-:-:-: h—t—‘—'§J‘a-——_“ o I 50 9 180 DAYS OF DECOMPOSITION - :GS «—-————«PMSO «— — ——«PMIO L- — — — — «UM2 «- --------- «UMos Appendix Figure 71. Decay oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. 0.4 0.5 0.3 UV ABSORBANCE 0.2 0.0 0.1 0 IO 25 so so 180 DAYS OF DECOMPOSITION rd yrs ,___.___.__spmao ~—- -—— -—~PM10 - - - - — iUM2 0- --------- oUMOS Appendix Figure 72. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 25°C. Absorbance oi UV light (250 nm) by various molecular weight iractions oi DOM, per 9 initial AFDN. FLUORESCENCE «H _E W“""— I—~— f. “a I ... s KP ulur L) a) 3:1 cl 3 v .I u. c> ‘- ‘T“‘c“‘*~~-— ‘ , '—' TT N M .—_— —- —" ’/;‘\‘S\.~ h ------ -. o 10 as so SC 180 DAYS OF DECOMPOSITION ; :63 s -—«PM30 -— — —*PM10 ._ ._ _ _ .. ‘UME «- --------- oUMOS Appendix Figure 79. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 10°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per g initial AFDN. 100 i FLUORESCENCE \ - — ~ - * — _ _ -.~~-fi'—‘:-'—"= ----------- ‘--~u--—:_:—:==M- - h I I o I I 0 IO 25 50 90 180 DAYS OF DECOMPOSITION = 463 = sPMSO «—— — ——«PMIO — — — - — «UM2 « --------- «(ms 1 Appendix Figure 80. Decay oi Scirpus acutus in laboratory under aerobic conditions at 10°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. 100 O m. LII D Z 0 DJ (0' 8 3 0 Egg- _l LL 0 N a 1'0 25 5'0 so 180 DAYS OF DECOMPOSITION : =GS ~———--——--——~PM3O ~—— -—- -—aPMlO - — — — — «UM2 ~ --------- «UMos Appendix Figure 81. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 10°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. 100 FLUORESCENCE 20 #* *’ *‘ #fl .50—--o..c_-u---4_-:-=-_'=.--=--:_‘='a O 0 10 25 SO 90 180 DAYS OF DECOMPOSITION : =68 = spMso «— — —-«PM10 -— - — — — «UM2 - --------- «UMos Appendix Figure 82. Decay oi Najas ilexilis in laboratory under aerobic conditions at 10°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per g initial AFDN. I I {II ir‘lllllll l I 100 8. ll] 0 z O LIJ (0' O (D 35 o S .- e .J LL 0 N o I I 1 I I -_-=.3—’!?- 0 IO 25 50 90 ISO DAYS OF DECOMPOSITION : sGS o——-— -— —~PM3O o—— -— --°PMIO «— - — — — «UM2 «- --------- «UMos Appendix Figure 83. Decay oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 10°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. 100 FLUORESCENCE SO 90 DAYS OF DECOMPOSITION l— — - — — «UM2 «- --------- «UMos Appendix Figure 84. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 10°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. FLUORESCENCE o r I r O 10 25 50 90 180 DAYS OF DECOMPOSITION ._. .... — — -— OUME 0' -------- ‘UMOS Appendix Figure 85. Decay oi Scirpus acutus in laboratory under aerobic-to-anaerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. O 3 O m. LI] 0 2 od LL] (9 o 0) [U m 0 D .J ll. / / “ r - OI I I I I o 10 as so so 180 DAYS OF DECOMPOSITION *- — —- — — .UME ~ --------- .UMOS Appendix Figure 86. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. 100 O m. I.” o z O I.” ‘9' Q (0 N o S «I .J u. ._‘:.:''---..._':-----.._-.-~—--._--..-'--.: 8% / O ,«sz'ZSZLTII ..... s-_-_.-:.:.:::.:.T.:::::=3L 0 IO 25 50 90 180 DAYS OF DECOMPOSITION : :33 —- —— —-oPM30 ~—- - —°PN10 ’- — '- — — ’UME? " --------- ‘UMOS Appendix Figure 87. Decay oi Najas ilexilis in laboratory under aerobic-to-anoerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 548 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. 100 FLUORESCENCE OI I I 0 IO 25 5'0 9 DAYS OF DECOMPOSITION L 303 : —oPM30 0— — —°PMIO :- - — — — «UM2 ~ --------- «UMos Appendix Figure 88. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDH. 100 0 mi I.“ o 5 8- 8 1:: ‘0‘? o s. 3 / .. LI. ’ f O \ ’ .- ’T N \ ’ 4" ’,,..c-"'. \ ,0 ‘--" - ______ : \’<:‘O"'-v o I I I I O 10 25 50 90 180 DAYS OF DECOMPOSITION : :GS «— — —«PM30 «-— — —«PMIo «— - - — - «UM2 «- --------- «UMos Appendix Figure 89. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDH. 100 80 5.0 40 FLUORESCENCE 20 O I I 0 IO 25 50 90 180 DAYS OF DECOMPOSITION «— - - — — «UM2 «- --------- «UMos Appendix Figure 90. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. 100 O m. DJ 0 z 0‘ LU (O O (O s : s :- 4 LI. 0 N () IO 25 «— — — — — «UM2 ~ --------- «UMos Appendix Figure 91. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. 100 60 so FLUORESCENCE 40 20 So so DAYS OF DECOMPOSITION : :G 3 —°PM30 ’— _ —.PM10 - - - - — «UMa «- -------- -«UMos Appendix Figure 92. Decay oi Scirpus acutus in laboratory under aerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. 100 O m. “J D Z O LIJ (0‘ O (D 33 o S .- .3 LI. 0 N O I 0 10 25 50 90 180 DAYS OF DECOMPOSITION : :98 : 3PM30 O—- — «—°PM10 «— - - - — «OMS ~ --------- «UMos Appendix Figure 93. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. 100 FLUORESCENCE O u 0 10 25 50 90 180 DAYS OF DECOMPOSITION : SSS «— — —«PMSO «—- -— —-«PMIo «- — — — — «UM2 «- --------- «UMos Appendix Figure 94. Decay oi Najas ilexilis in laboratory under aerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. 100 so 50 4o FLUORESCENCE 20 .... 0 To 25 5'0 9' 180 DAYS OF DECOMPOSITION «- — - — - «OM2 ~ --------- «OM05 Appendix Figure 95. Decay oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. O 2 53.4 m 0 2 LL! 0 (I) 3 Ms 0 __ ‘- ___;__ _.___ __ _,-_—.-—_::-"8 2) ...I u. ‘--*fl:'_.:v:."". -------------------- 0 5'0 9' 180 DAYS OF DECOMPOSITION I :03 ,___.___ ——~PM30 ~—- -—— ——~PM10 l- - - — — «OM2 ~ --------- «OM05 Appendix Figure 96. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 25°C. Fluorescence activity (activation 365 nm, emmission 545 nm), in relative iluorometer units, oi various molecular weight iractions oi DOM, per 9 initial AFDN. ID 0 H “'77 o (D c-o O 2: HO 5 .9. 8% At .A SZEE In .A -.~ 058‘ A A'OQ so it e “’1 w 3 LL<>: (3" a: v": Lo 3 h- : fig 5 8!: O C) 1 <3 £5 I <2 0' 0 TI I T r o 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 97. Decay oi Scirpus acutus in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). LO 0 H N O (D H o 2 H O 2 O A H H A A .— EI .A 5:35 a:&% 'cSEg 3: o t: ‘3 m. m 8 LL 0 o. 0 CI: V. .o a. '— S 5 g. o o O 35 ------------------- C: a- o 1 I ----“ -------------- I o 0 IO 25 so 90 180 DAYS OF DECOMPOSITION FUNC ............. COEFF A A A QCTUQL Appendix Figure 98. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). U) 0 F4 m o (9" <> 2: H O E. 2 S S '2 LIJ o ' Log m m. I'(D Q 3'. 8- E c: C) U: o 8. ° a:v4 "DEE *’ ul 5 84 0 ‘9 c: as ................................. q o- o I I I I TTTTTTTTTTTTTTTTTTTTTTTTTT ’0 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 99. Decay oi Najas ilexilis in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID 0 H m e (9" <3 :2 H O z:c> H H l- S s ,2; LIJ o 9 H aid) ’c>¢; "1 8 S ‘3 c: u.<> . ggca a:v* “ zsnag; *- 8 a 53..“ o o N.“ o {5 .......... <2 0. o ' ' I T'm--- o 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 100. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID 0 H m 7 o (9" <3 2 H O E 3 S 25 L” o L o H o: m“ 0 Q o H z¥<> it ca‘o' fig 40 3° Cl: <1" I'0 g '— 13. If. a. S F’ c: 8 <2 Q o i r O 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 101. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). L0 0 H m ,, o 0 fl '0 2 H O E. 2 C! O E Z "" LIJ LL] 0 ° H I” u .2. #°S 3 LI... .5 8- Q o U) Q “:¢> ‘3 a v. .0 E *- Pu 5 P..- o 32 c> w 5‘ ...... ~-~ o. 0" o I I W.-- T- I o 0 IO 35 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 102. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 10°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). u: o H m a (3" <3 2: H O z:c> H H t- S 2 .5 LIJ 0 ° H (rib ’C>c> 13:3, E} cg .A c3 u.c> :3" a:v* ALC’SE - 8 S s- : 32 .-_- <3 u1 _________________ <3 0. I ' I ------- $3M‘ o 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF .A A .A ACTUAL Appendix Figure 103. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 10°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). In 0 H N o (9" <3 2: H O E. 9. G o 5 L211 0 '2' DJ Aid) 'c323 :i .A LL . 0 LL ca‘o' A. E: . lnca “:¢> ‘3 a:g“ 'C’SE ,_ 8 E 8- o 32 <3 OI ‘ ___________________ <3 Q. 0 I I I TT w ----- T O 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 104. Decay oi Scirpus acutus in laboratory under aerobic conditions at 10°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). LO 0 H ‘3 <5 ‘2’ A H O s s S ° ’2 H LIJ LL! 0 . H M m. ’0 0 :Egg, E5 ‘3 c: S. o 3. ° a:v* "32E .- C.) if. 0. 2i 0 m (DATA 0F DAYS 2 AND TO EXCLUDED FROM FUNCTION) 0 3‘1 .................... 8 0" O I I I TTTTTTTTTT I. ----------------------- —_ ------ I 'O O 10 25 SO 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 105. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 10°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). L0 0 H m 7 O (D "I 0 2 H O 5. 2 a: (322 LZIJ o ": LU O! a)" ’0 8 13:3. E5 ‘3 HIE; Ll- A o °<>. . '>- azv- <3:I r- 8 S a. o 8 ---- ° In T ------------------------ <3 0' O I I I I TTTTTTTTTTTTTTT .o 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 106. Decay oi Najas ilexilis in laboratory under aerobic conditions at 10°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). In 0 H N A o (9" <3 :2 H O z:c> H c-o ._ 0: 8' A “o 8 33 8« A ”:5 C3 A c: u: o “ A 8 o ¢£ (3" a: vfi jar-o E \ 4A c: E x “‘ I.” 8‘ \s o g x“ o u: “‘ ----- c3 0' o I I I ----- -- U o 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ................ COEFF A A A ACTUAL Appendix Figure 108. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 10°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). In 0 H any . (9" ‘3 2: H O E 2 g ° 5 "in: LL! 0 ’ H m m. A ’0 Q 3: O A ll: :3‘9‘ A E: u: o 8. ° a:v‘ 'C’EE ,. 8 a a- 0 c: c: 3‘, _________________ ‘2 O. O ' I I “m' o 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ................ COEFF A A A ACTUAL Appendix Figure 109. Decay oi Scirpus acutus in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID <> w. my 0 (9" <> 2: H O z:c» H H '_ g 2 as a:&% 'C;23 :g IL :5 8- ‘g‘ o m o “z o ‘3 a:vJ -'C’EE (3 go 77 8 NI 2 ~ ....... o u: ________________________________ t? 0' o I I I I --- w .... " O 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 110. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). u) 0 H N, o (9" ‘3 2: HO 22 " i- mo°o «58 ° {2 :3 58 ‘3‘ .co 3" a:v- 'Cigg h- A E} E38 1 o 32 c> w <2 0'0 I IO 50 9 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 111. Decay oi Najas flexilis in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID 0 H N O (9" <> 2: H O E. 2 ¢ 0 E z: "ul LIJ ° H m 8 "O 0 ° [2 :3 as 8 mic? “'c> ‘3‘) a:v- ’C>EE ,_ 8 EEE: 4A ll c3 32 c: w °. a. I I I ' o O 10 25 50 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 112. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). I!) O H N ,7 . (9" <3 Z FHO a 9.. E o 5 05 (p b0 0 ‘5 8 E C’ c: m. o 3. ° a:v- LC’EE ,_ 8 O 35 .-_ <3 0' o I I TOE I ' I O O 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 113. Decay oi Nuphar variegatum in laboratory under aerobic—to-anaerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). In 0 H N O (9" C) 2: #00 E S g 2 5% LI] ’ H a:§§ 'C>c3 :5‘34 E5 9 «2 m o u. (’c’ (I? 8. $6 E *- 5 a- g c) c: a; ________________________ c> a. , , """ : """"" 1--‘““““"_"“"VC; ““ 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ................ com: A A A ACTUAL Appendix Figure 114. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID 0 H N o (9" c> 2: H O ZICD H H '- o: 8 is a "o 8 E :3 c: u.o Ego: a:v- «32; I'- A i 8 E 8 o c) <3 {5 <3 0' O I I Ti- I r I o. 0 10 25 SO 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 115. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID 0 H N ,4 o (9" C) 2: H O E. 2 s o '2 LLI o F: I.” lzcn (:23 H :3 u. :5 8 A . "’c: “:c, ‘9 a:v- (>3; ,_ 8 5 8 D 32 c: m ‘2 O. I I I O O 10 25 50 80 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 116. Decay oi Scirpus acutus in laboratory under aerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). c> 53 any . (9" <3 2: H O 5. 2 (I O '— 5 o A '2 5 a: m. '0 8 3?:3. is c: c: m. o 3 ° a v1 ’0 E g... {‘3 8‘ ‘5' ‘9 <> % 0. n.c, rc> 0 10 25 CO 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 117. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID 0 H m i o (9" <9 2 H O z. 2 .— E 3 E. L” o 0 H (K 0)‘ b0 0 . H 7: 0 Lu: ca‘o‘ g; u: o 3. ° a:v‘ "DIE ,_ 8 E 8- D 32 C) m <2 0' o I I I I-0 O 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 118. Decay oi Najas ilexilis in laboratory under aerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). o ‘3 n1, . (3" <3 :2 H0 52 9:! °5 LIJo ":LIJ 0=a> .c,z; 3-8 E C) <3 ":0 8,0 a:v- N32; ,.. 8 58 o 32 <3 tn ‘1‘? 0.0 IO 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 119. Decay oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID 0 H N . <3" <> 2 H O E 2 E o ’2' "" LIJ OJ C . H trip bom . H 2 LI. ea:8 in? “'c> ‘3‘, a:v* "32; g... 0 2 o , A A “0" L11 (‘1‘ \ O \\ O 33 x. C: 0. o I I -THI— I ‘O 0 10 25 SO 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 120. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 25°C. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID 0 H m , o (9" <3 2: H O E. 2 a: h- a o A fié m ml A Do 2 :;<> ‘3 32 em' ng a. 0 <2 ° azvd "32E *- 8 E. g. o C’ <3 as .............. q 0.. O ' ' “‘m r O O 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 121. Decay oi Scirpus acutus in Lawrence Lake littoral zone during spring and summer. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). in O H m o (3" ‘3 2: H O as .— EE YA ESE} DJ 0 ° H a m‘ '0 o :i u. a 8- Q . "’c) “z o ‘2 azv" <32; '- 8 58. o 3: <3 u! ‘3 0' I r-o 0 10 23 50 90 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 122. Decay oi Scirpus subterminalis in Lawrence Lake littoral zone during spring and summer. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). Appendix Figure 123. Decay oi Najas ilexilis in Lawrence Lake littoral zone during spring and summer. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). Appendix Figure 124. Decay oi Myriophyllum heterophyllum in Lawrence Lake littoral zone during spring and summer. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). o 3 m 77 e (D "" , ° 2 I H O ’ .2. 2 I g I” o .2 a "" LIJ LU o I 0 H 01 m‘ I. .o O o .I. H "= 8- E o I t; g 8 0 O. I II . )- a:v- , ’ 0<1: I- ,/’ 8 E 8. u‘dl’. o 0 ' O a: In .A {‘3 0' o f I I I I O 0 IO 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL ID 0 H N o (3" <> 2: H O E. 2 g o E UJ<> '753 m ml .0 o . H :3 u. a 8- a . l”<3 u. ‘A <3 ' O‘ I o )- a:g' "<: ,_ u‘i EEEB <3 32 c: w ‘2 0' O I #0 O 10 25 SO 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL ID 0 v-C o 9: o 2 H 0 Z O H 1". .- 0: 8' ’o 8 3' u. . 0 IL 9 ‘°‘ u, 8 u- o b o. O (i‘T‘ \‘H\ 'C>EE i- ‘~\\A 8 2 o ~‘~ o 8 N‘ 4 as ~~~~~~~~~~ a ........... l8. 0' O I I I I‘ ------ o 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 125. Decay oi Nuphar variegatum in Lawrence Lake littoral zone during spring and summer. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID 0 F. N . C9 "‘ O 2 H O E. 21 9.5 ° 5 as o. A A A -'-' E" a) ‘3‘? . A E Z é‘°°‘ .33 u.<> ‘3‘) ‘£.¢J 'c>3§ ._ 8 E g. (FUNCTION COULD NOT BE FIT) ‘3 32 8 LL! . 0" O I I I O o 10 as so 90 180 DAYS OF DECOMPOSITION FUNC ................ COEFF A A ACTUAL Appendix Figure 126. Decay oi Scirpus acutus in Lawrence Lake littoral zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID 0 H m , o (9" C’ 2: H O E. 2 A E3 .A 535? I“ o o E O! a)“ A A '0 O . H z o t: A ‘0‘ 3 mi 0 3. ° a:qa "DE; .— 5 g. 3 <2 <3 35 .--, o a - ------- . a O 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A ACTUAL Appendix Figure 127. Decay oi Scirpus subterminalis in Lawrence Lake littoral zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). to O H N . (3" <3 2: H O E. 5?. g ° '5 A "' Lu NJ 0 ° H (K m. A .0 O . A E "3 8- It. ‘3 c: a:v* "DIE ,.. 8 5 8- o 8 ”x o w “~-..__ 9 0' I T-” T I O 0 10 25 0 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 128. Decay oi Najas ilexilis in Lawrence Lake littoral zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). o 3 N O (9" ‘3 :2 H O E 2 2 ° 5 H NJ I.” 0 ° H “E °°‘ A A ‘° 2 1': 8- A E e '” 8 U: o, 9 a:g' "35; .- 8 a a. 0 U ”\‘ 0 IT] ““9_-~- 0. 0' O I7 I -m-jwr ' o 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ................ COEFF A A A ACTUAL Appendix Figure 129. Decay oi Myriophyllum heterophyllum in Lawrence Lake littoral zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). In <> «o N O (9" <3 2: H O z. 2 9.5 ° '2 O! a) .0 O . H "o 8 E“: C’ c: u.<> E;CJ GIV' "DEE ,_ Pu E 8 0 32 C) m °. a. I «a O 10 25 SO 80 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 130. Decay oi Nuphar variegatum in Lawrence Lake littoral zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). o ‘2 n1, . (9" <3 2: H O E. 5?. EE .A ‘32; A Fin: LI] 0 — ‘ H O! m' A '0 Q o H “o 8. E ‘3 <3 U: o 8. ° a:v‘ "32; P- n ‘9 . u: a g. -. o 32 " 0 w <2 0. o l‘ 1 'U r O O 10 25 SO 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 131. Decay oi Scirpus acutus in Lawrence Lake pelagial zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID 0 H “I, . (D F. 0 2 H O E. 2 a: <>*- El 0 A A A F: £29. 0: m‘ "0 Q :0 U. c553“ A tote? u. o ‘3 ° a:v‘ "DIE ,_ 8 Z o Q g at" (FUNCTION COULD NOT BE FIT) a: 8 m o O. O ' ' ' I O O 10 25 50 30 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 132. Decay oi Scirpus subterminalis in Lawrence Lake pelagial zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). o 59. m , o (9" ‘3 2 H O E 2 a! A ° '5 m mi A Do 0 "- 8- E" ‘3 c: u: o 3 ° 0: v‘ 'o E *- 8 5 a- o C’ c: g “- ~~~~~ o, 0' O I I'M-‘W r o 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 133. Decay oi Najas ilexilis in Lawrence Lake pelagial zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). ID O F! N . (9" ‘3 2 H 0 Z O H H l- s 2 a LL] 0 " H a: m' .0 O .i A u“ o. g. A L‘s . l0 8 U: o ‘3 a:g“ "DIE .. \ a g 8. °\\ 0 \ O 5 ~~ . ° 0. O r 3%“.- r ' O. 0 10 25 0 90 180 DAYS OF DECOMPOSITION FUNC ................ COEFF A A A ACTUAL Appendix Figure 134. Decay oi Myriophyllum heterophyllum in Lawrence Lake pelagial zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). 100 120 l T— PERCENT A.F.D.N. REMAINING 20 49 5:0 so D 50 DAYS OF DECOMPOSITION FUNC ---------------- COEFF .A A Appendix Figure 135. Decay oi Nuphar variegatum 180 in Lawrence Lake pelagial zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). 0.05 0.10 0.15 DECAY COEFFICIENT 0.00 A ACTUAL ID 0 H N . (9" <> 2 H O E. 2 .— g s: 5, g on A . H on A — O 8 :i u. c5 8‘ é o m o “z o ‘3 a:v“ "DIE O F' In .2. a- o g . o w ‘~‘ ..... o. 0. o-fl‘ I l O 0 10 25 50 30 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ncwnn. Appendix Figure 136. Decay oi Scirpus acutus in Nintergreen Lake littoral zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). 0.15 100 120 h t D D D 0.10 0.05 (FUNCTION COULD NOT BE FIT) PERCENT A.F.D.H. REMAINING 0 so 40 so so DECAY COEFFICIENT 0.00 '_ <> fb éE §5 so 180 onvs OF DECOMPOSITION FUNC ................ COEFF A A A ACTUAL Appendix Figure 137. Decay oi Scirpus subterminalis in Nintergreen Lake littoral zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). 100 120 I D 0.15 PERCENT A.F.D.N. REMAINING so 40 so so DECAY COEFFICIENT Q so so DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 133. Decay oi Najas ilexilis in Nintergreen Lake littoral zone during iall and winter. Percent oi initial ash—iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). u: 0 H N _ o (9" <3 5 o E 2 91‘. 2 ’5’, I.I.| ’ H acfig 'C>c> =2 0 t ‘2 m to g m. o °. ° cut!"I Nag; *’ u: E s« o " c> as t _________________________ q 0" O I I I ---‘: --------- fl ---- m.- F0 0 10 25 50 90 180 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 139. Decay oi Myriophyllum heterophyllum in Nintergreen Lake littoral zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). U) 0 H m 7 o (9" c: 2: H O 2:c> H H .— g 2 5 «8 68 :g u. c5 8 g o m 0 “:c> c3 a:g' 'c>55 *- 8 E58} :3 F’ c: 95 <2 °-<> c> 50 30 DAYS OF DECOMPOSITION FUNC ---------------- COEFF A A A ACTUAL Appendix Figure 140. Decay oi Nuphar variegatum in Wintergreen Lake littoral zone during iall and winter. Percent oi initial ash-iree dry weight remaining; actual data, values predicted by exponential iunction (FUNC), and decay coeiiicient oi the iunction (COEFF). 300 CK LL] 3 LI. .SJ on] 2: 1‘ F— .J S :8 2". H LI. 0 N o I I 0 10 25 50 90 180 DAYS OF DECOMPOSITION : :7. TNC 0— _ —*./o HEM °_-_-—../' CEL ._———-—.°/. LIG Appendix Figure 141. Decay oi Scirpus acutus in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 200 z 0F INITIAL TNC. FIBER 0 10 25 SO 90 180 DAYS OF DECOMPOSITION : Ax TNC :7 :x HEM ~——--——-——~Z CEL .____....y, LIG Appendix Figure 142. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 200 2 OF INITIAL TNC. FIBER 100 o I I I 0 IO 25 SO 90 180 DAYS OF DECOMPOSITION A :7, TNC ._..—— ._.°/, HEM ~—--—--‘—°'/- CEL o—-——-‘°/. LIG Appendix Figure 143. Decay oi Najas ilexilis in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. O O m a LIJ 2 U. (3 Z .— .J S L," 5. LI. 0 x OI I I I I 0 IO 25 50 90 180 DAYS OF DECOMPOSITION = <7. TNC 0— — —°°/. HEM °—-—---—'°'/. CEL ~—————o'/. LIG Appendix Figure 144. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 2 OF INITIAL TNC. FIBER ID as so so . 180 DAYS OF DECOMPOSITION r? =x TNC —-—--———-——»z HEM ~—---——--—ax CEL ————-muo Appendix Figure 145. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi initial content, on ash-iree dry weight basis, 0i total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. <3 <3 (p In n: In H u'o .<> CIGP z: .— .1 55:. F'c» HH. I‘WI.‘ IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII #9..." ccccccc g :rhq‘g: u. c: N O I I O 10 25 50 90 180 DAYS OF DECOMPOSITION = FSZ TNC r~* -% HEM = — - =Z CEL ....____.°/, LIG Appendix Figure 146. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 10°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 200 X OF INITIAL TNC. FIBER 8 " ‘ A 2.. "1‘ o N oooooooooo ’0’. ..... n---.;..;.;;o:_: ooooooo x j...— ‘°‘~.~ N -. ~ .. \#-—--‘--— 2.72:? .. o I T I I T O 10 25 50 90 180 DAYS OF DECOMPOSITION 3 t7. TNC — —— —-°'/. HEM '—-— - —°'/. CEL —————4Lm Appendix Figure 147. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 10°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG) in tissue. O O m I a: I. w E’. I u'c> l .0 2“" _____ - h- | ‘," ————— _' / So ' "\ // Zflunfz. ooooooooooooooooooooooooooooooooooooooooooooooooooooo H ' I*§--§ ____ ___ _..—-o “. ~.‘__' _____.-—-——-—-—-—‘ O x r o. ' 1 ' AW 0 10 25 50 90 180 DAYS OF DECOMPOSITION . :7. TNC = "/o HEM °—-—‘—°°/° CEL .————-uzus Appendix Figure 148. Decay oi Scirpus acutus in laboratory under aerobic conditions at 10°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG) in tissue. 300 200 2 OF INITIAL TNC. FIBER 100 O u 0 10 25 50 90 180 DAYS OF DECOMPOSITION : :7. TNC ———z HEM o——-—-—~°/. CEL .—————.'/. LIG Appendix Figure 149. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 10°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG) in tissue. 300 2 OF INITIAL TNC. FIBER o I I I O 10 25 50 SO 180 DAYS OF DECOMPOSITION , fly, TNC .___——.°/. HEM °—-—--—°'/o CEL —-———mLm Appendix Figure 150. Decay oi Najas ilexilis in laboratory under aerobic conditions at 10°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), Cellulose (CEL), and lignin (LIG) in tissue. 2 OF INITIAL TNC. FIBER 0' I I 1 - A 0 10 25 50 90 180 DAYS OF DECOMPOSITION : :7. TNC -——— —-'/. HEM °--—-—-°'/- CEL ~————mLm Appendix Figure 151. Decay oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 10°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG) in tissue. O O m a: DJ (D H “'0 .O c>nr Z r. .1 CI: ”*<> :2 00.0—000—00TOHO?00—00"0“nfi 2 H LI. 0 _..._.-===_"8 N o '—V 0 10 25 50 80 180 DAYS OF DECOMPOSITION e :7. TNC : H7. HEM ---—---°°/o CEL o——-- -‘°/. LIG Appendix Figure 152. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 10°C. Percent oi initial content, on ashriree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG) in tissue. 300 a: u: a: H “'c> .<> can” 2: '— .1 a: H<> :2 2: H u. c: N OI I I O 10 25 50 90 180 DAYS OF DECOMPOSITION : :x TNC = :z HEM ~—---——-—-—*% CEL o—————‘°/. LIG Appendix Figure 153. Decay oi Scirpus acutus in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 200 100 2 OF INITIAL TNC. FIBER O I I I 0 10 25 50 SO 130 DAYS OF DECOMPOSITION = :2 TNC E =2 HEM -—--—---—-*Z CEL ~————mLm Appendix Figure 154. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 I: u: a: H “'c» .<> £30? 2: .— .J :1 "c: :2 E u. c: 8 CI I I I 010 25 50 90 180 DAYS OF DECOMPOSITION : :°/. TNC —- — -—-°/. HEM o——-—-—-o‘/. CEL ...____.°/, LIG Appendix Figure 155. Decay oi Najas ilexilis in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG) in tissue. 300 200 100 2 OF INITIAL TNC. FIBER OI I I T O 10 25 50 90 180 DAYS OF DECOMPOSITION = ‘4 TNC = :2 HEM *—---—---——*Z CEL -— - — - — ox LIG Appendix Figure 156. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG) in tissue. 300 200 2 OF INITIAL TNC. FIBER 100 O 0 10 25 SO 90 180 DAYS OF DECOMPOSITION 2 :7, TNC —— _°./o HEM .__——-—o'/, CEL Appendix Figure 157. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. O O m a: U1 m H “.0 .o c>0r Z .— .J ‘5‘. S ~§-o r-s rz-oH ..‘.........../ ..................................... H LI. 0 x -~ZI“"—--o OI I I I I EL 0 10 25 50 90 180 DAYS OF DECOMPOSITION . -2 TNC ~————-% HEM °—-—'—°"- CEL —————«Lm Appendix Figure 158. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, 0i total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 a: u: 93 “'c> .<> ca“? 2: P— .1 SE :8 ... ———————— ° 2" 000.00.00.00; ooooooooooo /o o‘- "a ooooooooooooooooooooooo H / I“CL! \/ \;/\ x -‘\.\“,v’ '~._.———-———--——--—- ~:—--—‘—.- - O 9 180 DAYS OF DECOMPOSITION : :y, TNC .____..°/, HEM °—-—-—-°'/- CEL -——-—.°/. LIG Appendix Figure 159. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. O O m 0! U1 2 |"LCD .<:>d on! 2 F- l\. ’”\. .1 I \o” \\\ (I I \N. _____ 0 Ho «.. ————— *'<> HH‘N ........................................................ 5 \\ as $“"¢‘=:-~._. sN‘:-—_~_fi N “”M-:: OI I ' ' I fl‘ 0 10 25 50 90 180 DAYS OF DECOMPOSITION ; :7, TNC .__ —— —.°/, HEM .__..__-—..'/, CEL --———o°/. LlG Appendix Figure 160. Decay oi Scirpus acutus in laboratory under aerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, ai total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 \ a: / \ 36 / \ \ E / \ .53 / \'\. o N. / \ \ 55 / ‘ .J / E. o / :0 ..... thmz ........................................... z:" ‘~ H tlo"- ¥ x ——-— «nun—.— “—O— x _ .... — ———— —;—_—- -"-—":"‘ :-:.:-.---__—-——-~ 0. 22””: ——==_.._: 0 10 25 50 90 180 DAYS OF DECOMPOSITION 3 :y, TNC .____.y, HEM .—-—-—-°/. CEL ~————mLm Appendix Figure 161. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 200 300 z OF INITIAL TNC. FIBER 100 50 90 180 DAYS OF DECOMPOSITION : :7, TNC : =7. HEM 0— - -— - ——°./o CEL .—————~xuc Appendix Figure 162. Decay oi Najas ilexilis in laboratory under aerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG) in tissue. 300 35 a: \ "t \ " \ ‘ \ E2 ‘\ I" \ _| \ S \ t: /\ 55 ......................................................... u. o h x -~—--—-:":.::* ' 9" 180 DAYS OF DECOMPOSITION : E-y, TNC .____..°/, HEM .__-__..__.°/, CEL -——-—o'/. LIG Appendix Figure 163. Decay oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. c> c> a) a: in a: H u'c> .<> can? 2: .— .1 a: No ,,- _._, :2 l‘oooo}o“o..: 000000000000 T 0:0?0hfiugo: 0000000000000000000 E I ~~~~-h.~. :3 ‘=r‘*" ’"*'-*""—— -——. x ‘°‘--*-*--——--—-..__«..;:2._;:;i:;wg:::~j:::: OI ' ' . w 0 10 25 50 90 180 DAYS OF DECOMPOSITION : :2 TNC :, =2 HEM -------—*% CEL ._ - - — — .y, LIG Appendix Figure 164. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 25°C. Percent oi initial content, on ash-iree dry weight basis, 0i total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 200 X OF INITIAL TNC. FIBER 100 O 010 as so so 180 onvs OF DECOMPOSITION : 4y. me ————x HEM ~—-—-—o'/. CEL ~————.x LlG Appendix Figure 165. Decay oi Scirpus acutus in Lawrence Lake littoral zone during spring and summer. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (L1G) in tissue. 300 200 100 2 OF INITIAL TNC. FIBER o I I I 0 IO 25 SO 30 180 DQYS OF DECOMPOSITION ; :x TNC 5* :z HEM ~—---—---*% CEL o———-—«'/. LIG Appendix Figure 166. Decay oi Scirpus subterminalis in Lawrence Lake littoral zone during spring and summer. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 a: u1 «1 H u’c> .c: C)OV z: .— .1 S r-€>’ HH 2: H u. c: x 50 90 DAYS OF DECOMPOSITION : :7, TNC ._— — _.°/, HEM .._-_-__.°/, CEL o—-———.°/. LIG Appendix Figure 167. Decay oi Najas ilexilis in Lawrence Lake littoral zone during spring and summer. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. <3 c: a) a: u1 «1 H LI’8 /\ 6m“ \ / \ Z " \ é \ :8 OOOIIOOOOOOOOOO\’OO OOOOOOOOOOOOOOOOOOOO O OOOOOOOOOOOOOOOOOOOO 2H H % \\\‘\. x s\‘, O' I ' 1 I‘m 0 10 25 50 90 180 DAYS OF DECOMPOSITION = :% TNC >e =2 HEM ~—---——-—-—~% CEL ---——.°/. LIG Appendix Figure 168. Decay oi Myriophyllum heterophyllum in Lawrence Lake littoral zone during spring and summer. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 0! DJ in H I'I'O .O can“ 2 .— _l S. *8 2“ .4‘.N.;.;:. ......................................... lL \—-"\ ——————————— O x .TT"' —17;—---------—=1?L:T=1;:fir:;::fi; o f ; T M O 10 25 50 90 180 DAYS OF DECOMPOSITION - 47. TNC - :7. HEM ._-_-__.-/, CEL .-————.-/. LIG Appendix Figure 169. Decay oi Nuphar variegatum in Lawrence Lake littoral zone during spring and summer. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 200 z OF INITIAL TNC. FIBER 100 ISO 50 90 DAYS OF DECOMPOSITION = 4% TNC = :2 HEM ~—---——-———~% CEL ~-———mLm Appendix Figure 170. Decay oi Scirpus acutus in Lawrence Lake littoral zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 tr u1 «1 H u'c> .<> c10r Z *- § :8 EH u. c: X o I I I I 0 10 25 50 90 180 DAYS OF DECOMPOSITION : :7, TNC .——————-—-°/. HEM .._..._-.._.°/. CEL -————.°/. LIG Appendix Figure 171. Decay oi Scirpus subterminalis in Lawrence Lake littoral zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 200 100 u i 3 :t St 31 2 OF INITIAL TNC. FIBER o I I I I 0 10 25 SO 90 180 DAYS OF DECOMPOSITION : 47, TNC : 47. HEM h.-_-—../o CEL -——-—.'/. LIG Appendix Figure 172. Decay oi Najas ilexilis in Lawrence Lake littoral zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 200 100 x OF INITIAL TNC. FIBER o I I r r O 10 25 50 90 180 DAYS OF DECOMPOSITION : :7, TNC 0—— —— -—°./o HEM °—'_"—°./' CEL -——--«°/. LIG Appendix Figure 173. Decay oi Myriophyllum heterophyllum in Lawrence Lake littoral zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, Oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG) in tissue. O O m a: I.” 3 “'0 .0 c1“? 2 .— .J C Ho *~—. :0 g .5 00000000 .35....mI-I’ “0.70:0:07 00000000000000000000000000 E f" ‘9 -_—-__'-———-—__ c: --~.‘~ x Afi_ 0" I I 4 0 10 25 50 90 180 DAYS OF DECOMPOSITION es :2 TNC t -*Z HEM ----—-'--—*% CEL .-———--v/. LIG Appendix Figure 174. Decay oi Nuphar variegatum in Lawrence Lake littoral zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 0! DJ 29. “.0 .8. ‘2’ i\ i- I\ a’ , x..- Ho - —————————— _. .".'.° ., ............................ 53" ..;:T:;: ll. 0 N O'I| I I I O 10 25 50 90 180 DAYS OF DECOMPOSITION : =7. TNC 0—- -— --°'/. HEM ._-—-——.°/, CEL 0-—-———‘°/. LIG Appendix Figure 175. Decay oi Scirpus acutus in Lawrence Lake pelagial zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. c: O (D E .9. ,'\ Ll'8 1‘ 661' \ z: '— .1 So 52 2: H u. c: :« OI I I I I 010 25 50 90 180 DAYS OF DECOMPOSITION > :7. TNC -—- — —-°/. HEM o—-—-—°'/. CEL -—-——.~/. L16 Appendix Figure 176. Decay Oi Scirpus subterminalis in Lawrence Lake pelagial zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 DC I.“ S “-0 .0 L10“ 2 '— .J so 52 5 U. o N o I I I I 010 25 50 90 180 DAYS OF DECOMPOSITION -. :7. TNC ‘-—-' -— —°.°/. HEM ‘—-—-—-°°/. CEL -__.__.-/, L16 Appendix Figure 177. Decay oi Najas ilexilis in Lawrence Lake pelagial zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. c: c> a) 1: u1 S “'c> .<> on! 2: I‘- .1 S :8 zI-I I-O LL :3 N o I I I I 010 25 50 90 180 DAYS OF DECOMPOSITION .. :2 TNC es -—~% HEM ~—---——-——~% CEL ---——o°/. LlG Appendix Figure 178. Decay oi Myriophyllum heterophyllum in Lawrence Lake pelagial zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG) in tissue. 300 a: LIJ 2 “'0 .O LIOP 2 .u— .1 S :8 ______ z“ oooooooooooooooo “~o~o*oo-_o‘ ooooooooooooooooo ‘35 -\-r‘ "“‘----.._.-_______: R - so ' 180 DAYS OF DECOMPOSITION : :7. TNC .-————.°/. HEM .-—-—-—-°/. CEL -————.z L16 Appendix Figure 179. Decay oi Nuphar variegatum in Lawrence Lake pelagial zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM). cellulose (CEL), and lignin (LIC) in tissue. 300 200 2 OF INITIAL TNC. FIBER 100 o I I I I 0 IO 85 50 90 180 DAYS OF DECOMPOSITION L :7, TNC ,____..,, HEM ~—-—-—o'/. CEL .————-uzuc Appendix Figure 180. Decay oi Scirpus acutus in Wintergreen Lake littoral zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 2 OF INITIAL TNC. FIBER o I I W I 0 IO 25 50 90 130 DAYS OF DECOMPOSITION ; :y. TNC ._____..y, HEM -—--——---'/- CEL .. - — — — «7. L16 Appendix Figure 181. Decay oi Scirpus subterminalis in Nintergreen Lake littoral zone during iall and winter. Percent oi initial content, on ash-tree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 goo \ / / 2 OF INITIAL TNC. FIBER 100 O I r i I 0 10 25 50 30 180 DAYS OF DECOMPOSITION = :z TNC ?’ -—*% HEM ----—-‘--—*% CEL .- - — — — ax. L16 Appendix Figure 182. Decay oi Najas ilexilis in Nintergreen Lake littoral zone during iall and winter. Percent oi initial content, on ash-tree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. . 300 200 100 2 OF INITIAL TNC. FIBER O I I I 0 10 25 50 90 180 DAYS OF DECOMPOSITION ; 47. TNC ~—-——-°% HEM ~—-—"—°°/° CEL o—----—*°/. LIG Appendix Figure 183. Decay oi Myriophyllum heterophyllum in Nintergreen Lake littoral zone during iall and winter. Percent oi initial content, on ash-iree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 300 200 100 10 E. ‘. / : 2 OF INITIAL TNC. FIBER 180 50 80 DAYS OF DECOMPOSITION r :2 TNC = 4% HEM ~—---——-——~% CEL --———.°/. L16 Appendix Figure 184. Decay oi Nuphar variegatum in Nintergreen Lake littoral zone during iall and winter. Percent oi initial content, on ash-tree dry weight basis, oi total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG) in tissue. 0 n1 8 (D *— Z I.“ U) f tnzz H. five a ‘z’ ‘8 F' C) .— 22 a: m “J o m a H m LL “- r- ID‘ 2 DJ 0 a: I.” O. 90 DAYS OF DECOMPOSITION ;. :z TNC - -*% HEN *-'-‘——”"‘“” CEL o——-——¢'/. LIG Appendix Figure 185. Decay oi Scirpus acutus in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 60 O N 1. \ / .1 PERCENT TNC PERCENT FIBER COMPONENTS so 80 DAYS OF DECOMPOSITION - :7. mo . =7. HEM -—— - —— - —-'/. CEL I:———-uzue Appendix Figure 186. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 2O 60 m .— z In m‘é’ Ha PVC ‘9 E z: c: I- ! 0 F0. o—. O EI'IA -‘\\\ '0185 Q I \ - 2 E Vmflflxfi “-___~. ml fl.”IO--.__~-~ ..t£‘% /..-v o———- a l’ 3: OI I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION ; :‘I. TNC — -— —0./. HEM .—--—"—../o CEL .- - - — — .7. L16 Appendix Figure 187. Decay oi Najas ilexilis in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). O O N (D (D .— Z 'i’ a. '8 O o 0. Z 5 F' C) r- L.,C>ag E ”g E /. LI. a. In)- «/" 'Tifi / .- -‘ fibu- __ \ CI. 8 O. o I I I I I O O 10 25 50 90 180 DAYS OF DECOMPOSITION : fly. TNC 3 £7. HEM 0'— - — - —-°°/. CEL — — - - — «7. L16 Appendix Figure 188. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi ash-tree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG). 60 20 15 5 PERCENT TNC s 10 50 PERCENT FIBER COMPONENTS 0 IO 25 50 ~ 90 180 DAYS OF DECOMPOSITION : :7, TNC : £2 HEM .— " _ "' —°./o CEL ~————mLm . Appendix Figure 188. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). O O N (.0 (D .— 2 E! 52. 4a,: 23 ‘~\~ __ SE l-O K ’.“~ “hwy-'- on: ZI-c“ / .. 'mm In I “'~-.. «I o ~N————-—-——-—'—-O H E} lL 0- F- U). H5 0 0! LL! -___._____;/ a O I— O 10 25 50 90 180 DAYS OF DECOMPOSITION e. Hex TNC .; =2 HEM ~—-—-——-——~% CEL ~——-—«Lm Appendix Figure 180. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 10°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 ID ID v-O .v 0 Z *— D—O Z". D m ('0 O a: m 0' U) 5 0 PERCENT FIBER COMPONENTS ”6 1'0 55 5'0 9'0 180" DAYS OF DECOMPOSITION ————o°/. TNC ————-.-/. HEM .———-—.-/. CEL .— — — — — .7, L16 Qppendix Figure 191. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 10° Percent oi ash- iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 9 O (D '— Z Li‘ 9 -‘<’r’o ° % Z __._.__, D l- V—wywr: fih... . 0 ho v/ ‘~—"-——-_-_~__ 0 Est, mm 0 93. E? u. m 49.5 '0———_ LU I ” ---- -° 0 _o—_ ’f” fi ‘0- — _- 0. 0' l I I l U 0 10 25 50 90 180 DQYS OF DECOMPOSITION ~——-—°°/. TNC 0— —— —°'/. HEM 0-—-—-—0°/. CEL ~—————«°/. LIG Qppendix Figure 192. Decay oi Scirpus acutus in laboratory under aerobic conditions at 10°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 (D *- z m m‘é’ v-o‘ 'v8 0 / 0 ES __,...» ~--.._ \fim 0 ‘~ 0 m H LU ll. 0. .— ID 42:: LIJ 0 01 ll] 0. ~“flfih---—~I— {/40 <> ,- o 10 as so so 180 DRYS 0F DECOMPOSITION : =7. TNC ~——-—o°/. HEM .—-—-——~'/. CEL ~-——-mLm Qppendix Figure 193. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 10°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL). and lignin (LIG). 20 60 PERCENT TNC PERCENT FIBER COMPONENTS OI I I I I O O 10 25 SO 90 180 DRYS OF DECOMPOSITION ;, :2 TNC : :x HEM ~—---——-——~% CEL .. — — — -— 0?. LIG nppendix Figure 194. Decay oi Najas ilexilis in laboratory under aerobic conditions at 10°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 (D '— z LIJ ‘2- .95 o O. z 5 F’ c: h-C) <3 2"! 5mm ‘6‘ E El fiat-"fl". LL 0. 35 g I.” ha“ o “J O. ' O 90 180 DQYS OF DECOMPOSITION ; :7. TNC -———-——~°/. HEM .—-—--—-'/. CEL ~————«Lm Qppendix Figure 195. Decay oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 10°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). O _O N (O (D '— 2 g 22. 9° g E E 8 {153' “8% C) 12 ..—-- u :{;:-___.p,|gtz- -———.___,___‘ tn 0 0! DJ 0. O I I O 010 25 50 90 180 DRYS OF DECOMPOSITION ; :7, TNC o— —— ——o'/, HEM 0—--—-—°./o CEL ...._.___.°/, LIG Qppendix Figure 196. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 10°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 5 5 co F- 2: g d (2" ’V'Ef z 5 *' c: F" . "fin—open: Ei u. a. £5 OJ L) ____r—~~f El —' (L <3 50 90 180 DQYS OF DECOMPOSITION t <7. TNC h— —- —°'/. HEM o-—-—-—°'/. CEL —————mLm Qppendix Figure 197. Decay oi Scirpus acutus in laboratory under aerobic—to-anaerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (L16). 0 N 60 5 J PERCENT FIBER COMPONENTS PERCENT TNC 50 90 DRYS 0F DECOMPOSITION S Sax TNC : E12 HEM ~———-——-—-—~% CEL o——-—--*°/. LIG appendix Figure 198. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL). and lignin (LIG). 8 8 U) I- E R .S E O. ‘73 s P-€> <3 5 fl. \ hm % 8 2 [LI LI. 0- 'a\ r- ID‘ V!" -\ PH El 0* “N ./ ~~\- — —-- — — — 3 [LI 0. O I I F O O 10 25 50 90 180 DQYS 0F DECOMPOSITION E :y, TNC ._______.°/, HEM -—--—-——o°/. CEL ~————mLm Qppendix Figure 199. Decay oi Najas ilexilis in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). c: c: n: (D a) .— z: E 52. .gigz " z: E 8 P—C) ‘3‘! 2 H. hm S E-‘i 3} IL 0- ID!— .H 2 u: C) a: u: a. no 50 90 180 DQYS OF DECOMPOSITION = :‘l. TNC .-—-—-—-°'/. HEM °--------—-°°/. CEL ~————mLm Rppendix Figure 200. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 CD .— 5 In. 1.02 o" "'8 Z 5 8 h-C> ‘3 Z". lmm 3 E E} IL 0. ID.- h'v--IZ DJ O at LI] 0.. OI'I I I 'O 0 10 25 50 90 180 DRYS 0F DECOMPOSITION :7 :2 TNC f :2 HEM ~—---——--—*Z CEL o——-——.-/. LIG nppendix Figure 201. Decoy oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG). O O N (D (D .n- 2 w a. .3 g ‘2’ ’\ E .- K‘\\ /.\ 8 .— 2 ho I! t \: ‘\~\ ”g {5 -.-,___._____,_,..____ IL ml “-5-“..pd z 0— — \ 8 se’ ------ ~~ g —=L““‘ ~._;; "" ‘\~ a. fi—T‘T} I I o 0 10 25 50 S 180 DQYS OF DECOMPOSITION ‘r 3% TNC 3 47. HEM *— - -— - —-°°/. CEL —————mLm prendix Figure 202. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 8 8 a) '— Z “J Le. .95 3 % +- 8 "2'2- ~83, 8 A 2 E} //’ ‘\\\ ‘__'._ _,, u. a. \ / ****** .g-u—qu I‘- ll) / //\_ _____...__—--- HE! \‘ l ,.__.-—-_—-—.—-—-.—o o \x‘w'Ifi-’ 83 T. O. 0' § '- A0 50 90 180 DRYS OF DECOMPOSITION g :7, TNC _ _ —-°/. HEM ~—-—-—-°/. CEL ~-——-0°/. LIG nppendix Figure 203. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). O O N (O (O '- Z .0 mg w" *g-ca c: ,A*\\ £5 2 K .- yo/ \ 8 ZI-I' \~ hhfi .03” u: ‘-- ‘“ d) 8 ‘-~_--.l—— ’. H -h- - LL E .. ...... ._. .. ID I,” ’v-ILZ“ “-90,”. —————— r 3 UJ // a. OI I I I I o 0 10 25 50 90 180 DRYS OF DECOMPOSITION E 4&2 TNC : :2 HEM ~—---—---~% CEL ———-—mLm prendix Figure 204. Decay oi Scirpus acutus in laboratory under aerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 a) ’- E5 (0 m2 '4 bq-o c: (L z: 2% F' co r—c: C’ 2". pm“ 3 ii {5 II a. ID 4352 In C) I! u: a. c: N: 0 10 25 50 90 180 DAYS OF DECOMPOSITION ;, :2 TNC : :2 HEM ~—---——--—~% CEL o——--—«'/. LIG Appendix Figure 205. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 60 20 is PERCENT TNC 5 f5 0 PERCENT FIBER COMPONENTS o I I I I o O 10 25 50 90 180 DQYS OF DECOMPOSITION >7 =% TNC 3 :% HEM *—---—---*% CEL —--——mLm Appendix Figure 206. Decay oi Najas ilexilis in laboratory under aerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 8 8 (D .— 2 DJ EB- Pv-E; o O. E x ————— 5 h- /J/ "° C) 2 ’(O m 3 ”3' E; u. .u #- / 'I-O Z m£.:.___. g 0: —- I.” 0. f. ' _ f o 50 90 180 DAYS OF DECOMPOSITION ; :‘I. TNC o—— —— —-o'/. HEM — - — - —°./o CEL ———-—«Lm Appendix Figure 207. Decoy oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). O O N (0 CD '— z E :9.- ‘9 P g E P 8 F-EL bc’OC r m as O: '\ — '- "“" ‘- fi .- ‘t I: 0- "7’; -- _...- -———-—- r 8 1 3 ~ 5 (L O I I 1 I o 0 IO 25 50 90 180 DQYS OF DECOMPOSITION 3 3% TNC 3 3% HEM 3 -‘ - 3% CEL .———--uzuc Appendix Figure 208. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 25°C. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 (O .— I?! ID. [02 —0 PV'Ez U ‘h-“ z I-O 2". .8“ w LIJ o m m H w LI. 0. ID?- ID ”—02 [LI 0 0! U1 0. o 10 as so 90 180 ° DAYS OF DECOMPOSITION T 3<% TNC 3 4% HEM *—---—---—*X CEL ~————4Lm Appendix Figure 209. Decay oi Scirpus acutus in Lawrence Lake littoral zone during spring and summer. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). O O N (D (D *— 5% ID Z '4‘ iv 8 g2 z: .— O O I'- O a 'P E Q m m H LIJ LL 0. '— 42:: LU D (Z LL! 0. so 90 180 DAYS OF DECOMPOSITION ;. =z TNC : :z HEM ----—---—~x CEL ~————mLm Appendix Figure 210. Decay oi Scirpus subterminalis in Lawrence Lake littoral zone during spring and summer. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 SO (D .— 5 '2. .S E g E P 8 E 2. '85. 59‘ .9. LIJ LI. 0. A m.\ V— DIR. g LIJ 0. O F I I I " 0 10 25 50 90 180 DAYS OF DECOMPOSITION : :7, TNC — —- ——O°/. HEM 0—— " "'— - —"./o CEL —————mLm Appendix Figure 211. Decay oi Najas ilexilis in Lawrence Lake littoral zone during spring and summer. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). O O N (.0 (I) .— Z ‘é’ *" 43¢: 0 % z: c: F’ C) PO O: 2".- hm 25' 0‘9 g g; "K’II '” IL ‘x. JD)- ID )\. HE D 0: LI] 0.. o I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION ; :‘l, TNC % 47. HEM *— " — " —°'/. CEL - -- - - - 37. L10 Appendix Figure 212. Decay oi Myriophyllum heterophyllum in Lawrence Lake littoral zone during spring and summer. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 15 (D .— Z In m‘é’ v-c“ 'q-o o O. 2 2‘3 .- Q F-C) c) z—c' Dma" 23 In M o-c M LI. 0.. i- Z In 0 (Z Lu 0. O ' I r0 0 10 25 50 90 180 DAYS OF DECOMPOSITION ? 37. TNC 3— —- —3°/. HEM *— - —- - -—°'/. CEL —————¢Lm Appendix Figure 213. Decay oi Nuphar variegatum in Lawrence Lake littoral zone during spring and summer. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). c> c: n: (o a) P- z: u: 9- P93 5 g:: o. ‘2) >-:-_--——.-____fi__=_-___. g F- Tl ”T" C’ h-C) (z z: . no S " E E; IL aor- ID H E L) I: r~ E O I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION ; =7. TNC 3 .,O HEM _ - — - ——-'/. CEL -————-xuo Appendix Figure 214. Decay oi Scirpus acutus in Lawrence Lake littoral zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 8 8 (D .—- 2 LL] d IDZ I-O PVC 0 ,_ 95 E _—_-.-—_-——~——_—-——~. 8 "i-un...‘ 52‘ .v -""'"-—_.-_ “N .36 E? IL m. .fl’z‘ LL! 0 m. c. __ #7:: LL] I \.—-_ —————— a- O I I I o O 10 25 50 90 180 DAYS OF DECOMPOSITION r :2 TNC 3* :2 HEM ~—--——---——*% CEL ~-——-—«'/. LIG Appendix Figure 215. Decay oi Scirpus subterminalis in Lawrence Lake littoral zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG). o, O N (.0 (D '- Z Li‘ 3 338 " 1: E I ”SI-u..- : 8 ggd\-_.I/ M-.‘—'--—. ngfi g; Ins. 53 u] / \,____~. u. 'D ,,._f:72—-r "”EE pK~.——‘-“"--—- g LL! 0. O I I I I o 010 25 50 90 180 DAYS OF DECOMPOSITION 3 3% TNC 33' 3:2 HEM *—---—---—*% CEL -- — - —.'/. LIG Appendix Figure 216. Decay oi Najas ilexilis in Lawrence Lake littoral zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 15 20 ED is PERCENT TNC Io \\7 I So PERCENT FIBER COMPONENTS o ' I ' I I o 10 as so so 180° DAYS OF DECOMPOSITION s :2 TNC o————-°/. HEM -—--—-——.°/. CEL ~————muo Appendix Figure 217. Decay oi Myriophyllum heterophyllum in Lawrence Lake littoral zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). O O N (.0 m .— Z .9 S H. bvo o O. 2: E5 *’ c2 *’ 53:2 35 ‘”l” O 3 I! -M' ...—-""'""" ”~‘fi ’c-IZ LU 0 0: DJ 0. I» c: 50 9 180 DAYS OF DECOMPOSITION : 4.7, TNC : 3% HEM “"""" "’ _ " —"'./' CEL —————mLm Appendix Figure 218. Decay oi Nuphar variegatum in Lawrence Lake littoral zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (L16). 8 8 (D .— z to m‘i‘ OH. Ive .- 2 PO 2"! hm“ B E E, D. ID #332 LU Q 0! —————— U1 0.. O I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION ; :7. TNC —— —-o°/. HEM -—-—-——-°/. CEL o——-—-.'/. LlG Appendix Figure 219. Decay oi Scirpus acutus in Lawrence Lake pelagial zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). O O N (O 0') .u— 2 m‘i' "d nvo 2 L...» E .— fl‘hW-fl’fl—T 8 52. ,....--—--———--------° mg g \/ a 3: " “- I0‘ 4222 \ 8 / a: ... "- ------ __..__ — :1 m on ___ 0. CI I I I I O O 10 25 50 90 180 DAYS OF DECOMPOSITION ; =7. TNC 3 =7. HEM ~—-——--—°’/. CEL --——--—.°/. LlG Appendix Figure 220. Decay oi Scirpus subterminalis in Lawrence Lake pelagial zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 U) I- Z E‘ b9& 0 Z 5 8 I- on: 2 'm ‘6‘ *é.‘ E? IL Int /\ ~___ -35 ’ \ x, ——————— O 8 r 5 0.. O I I I I O O 10 25 50 90 180 DAYS OF DECOMPOSITION r :7. TNC °-—— —— —-°'/. HEM ---—--——0'/. CEL --———-¢'/. LIG Appendix Figure 221. Decay oi Najas ilexilis in Lawrence Lake pelagial zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). O O N (.0 (O .— 2 E‘ 3- I've g E ,_ 8 PO 0: ZH' pm 23 E-‘é E? IL -‘25 DJ 0 a: DJ 0. OI I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION 3 3% TNC 3 3% HEM ~—---——--—*Z CEL °-——--3'/. LIG Appendix Figure 222. Decay oi Myriophyllum heterophyllum in Lawrence Lake pelagial zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 (D I'- 2 DJ ID 2 H. EVE ‘z’ s F' c: F-C) C’ 2". 5mm 35 IL 0- ’*-—-—--—...——-_.r--".__":-:...’: '9'- ID #1,...”- d PHI-Z” ~—-"‘-— ‘--~—; 0 \I " 35 ‘s” a. OI I i I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION :3 3% TNC 3 3% HEM '~—---—---—*% CEL -—-—-uxuc Appendix Figure 223. Decay oi Nuphar variegatum in Lawrence Lake pelagial zone during iall and winter. Percent oi ash—iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 H. Iv- D Z r- F- c: E5 0 m LIJ 0. ,l0 H S PERCENT FIBER COMPONENTS O I I I I I O 0 IO 25 50 9 180 DAYS OF DECOMPOSITION 3 3°/. TNC 3—- — —-°'/. HEM 0— - — - -—°°/. CEL ~—--—4Lm Appendix Figure 224. Decay oi Scirpus acutus in Hintergreen Lake littoral zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 20 60 is PERCENT TNC é PERCENT FIBER COMPONENTS OI i I I I O 10 as so 90 180° DAYS OF DECOMPOSITION . =7. TNC -———z HEM ~—--—-—~z CEL —————mLm Appendix Figure 225. Decay oi Scirpus subterminalis in Nintergreen Lake littoral zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LlG). 20 60 (O I'- 2 u:%! Ivo Q 0. Z Z I- O O .- Om D ES ‘PIu Q m O! H LIJ ll. 0. ID.- -v-Cz DJ 0 0! DJ 0. O I I I I O 0 IO 25 50 90 180 DAYS OF DECOMPOSITION ; :7, TNC : £7. HEM 0'"— - _ " —../o CEL —————mLm Appendix Figure 226. Decay oi Najas ilexilis in Nintergreen Lake littoral zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). 8 8 ID. [D H ’V O z .- .— E 2' b8 0 tr LIJ 0. ID O 50 90 180 DAYS OF DECOMPOSITION : o—————0'/. HEM o-—-—--—°°/. CEL ~————mLm Appendix Figure 227. Decay oi Myriophyllum heterophyllum in Nintergreen Lake littoral zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). O O N (.0 ID ID 0".- IV 0 Z '— h-cn .C’ s. 3 P Q (X LU “- In m. .fl I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION 3 3 47. HEM 3'— - -- - -—3°/. CEL ————-mLm Appendix Figure 228. Decay oi Nuphar variegatum in Nintergreen Lake littoral zone during iall and winter. Percent oi ash-iree dry weight oi plant material as total nonstructural carbohydrate (TNC), hemicellulose (HEM), cellulose (CEL), and lignin (LIG). PERCENT FIBER COMPONENTS PERCENT FIBER COMPONENTS 50 800 O. .\ O V x O x D ./ T‘x ‘° 8- \ g; / \ .8 :2 cr. 0 \ T m m- / \ / \' 8 o“ *m O Fry/[IX I I 4 i O 0 10 25 50 90 180 DAYS OF DECOMPOSITION :3 3ATP -—--——— -—-ETS Appendix Figure 229. Decay oi Scirpus acutus in laboratory under aerobic—to-anaerobic conditions at 10°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. 800 50 40 \ / <1 \ 400 600 ATP ETS o <" ‘~, / \ 200 O 0 DAYS OF DECOMPOSITION e: cATP = =ETS 180 Appendix Figure 230. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 10°C. ATP content (Mg ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. 800 8 I / "D o. .‘E .. /,/ -§ :2 c :3. ’\\ a,zr “1 // \\\ ,I" c: «2” _c> <3.l N °o IO 2"; ' ' 180° 50 90 DAYS OF DECOMPOSITION c :ATP Appendix Figure 231. -— — -—oETS Decay oi Najas ilexilis in laboratory under aerobic-to-anaerobic conditions at 10°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O 8 / 8 O v. // .8 O mi a. ///’ $30) I- 'V .— °:c> // u: N. l/ c: O O 'N H- O f I I I O 0 1 25 50 90 180 DAYS OF DECOMPOSITION . SATP —— — —oETS Appendix Figure 232. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerobic conditions at 10°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O 8 8 O O ’(O O E O O I'(‘J O I I I I r 3 O 0 IO 25 50 90 180 DAYS OF DECOMPOSITION ' .3 :ATP ~--- — --oETS Appendix Figure 233. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 10°C. ATP content (Do ATP) and ETS activity (relative absorbance units) per g ash—iree dry weight oi plant tissue. O O O U) (I) v. 8 .(D O .\ ('0' / \ O a. ‘*- c>09 P- ,// T“~ 'v-F- \ I K O I I I I O 0 IO 25 50 90 180 DAYS OF DECOMPOSITION :— SATP -——— — —-ETS Appendix Figure 234. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 10°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. 50 800 600 400 ATP ETS 0 / t L / 500 '8 *\v’,r3 A : %< O I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION e :ATP —— — -—~ETS Appendix Figure 235. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 10° C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash- iree dry weight oi plant tissue. 50 800 ATP O I I I I O 50 90 DAYS OF DECOMPOSITION : :ATP -— — —-ETS Appendix Figure 236. Decay oi Scirpus acutus in laboratory under aerobic conditions at 10°C. ATP content (pg ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. 800 O O '(D O O. O (D E T E O O 'N O r r I I O 0 IO 25 50 90 180 DAYS OF DECOMPOSITION E :ATP .3 =ETS Appendix Figure 237. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 10°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. 50 800 ATP 50 90 DAYS OF DECOMPOSITION : =ATP .__ —— -—+ETS Appendix Figure 238. Decay oi Najas ilexilis in laboratory under aerobic conditions at 10°C. ATP content (Mg ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O O O u, ’g."‘- "". (D an!” \ x / o. / \ ”flu- O at / a. 53 r- ’V' (rig-l z// c: an ‘33 O T I I I o 0 10 25 180 50 90 DAYS OF DECOMPOSITION ~——--——— -—~ETS Appendix Figure 239. in laboratory under aerobic conditions at 10°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. Decay oi Myriophyllum heterophyllum c: c: c: In fi> ”’1; (n f \ o \ / \ V" I \v 8 no cad I “’ c: a. c: '- Pv (I‘D‘V “- c> <> <> “U H. g -: I I 1 o 0 10 25 180 so so onvs 0F DECOMPOSITION s~ eaeTP = :ETS Appendix Figure 240. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 10°C. ATP content units) per g ash-iree dry weight oi plant tissue. (pg ATP) and ETS activity (relative absorbance ETS ETS 400 600 800 ATP ETS 200 O. I I I 0 ID as so so 130° DAYS OF DECOMPOSITION % 4ATP —— — —ETs Appendix Figure 241. Decay oi Scirpus acutus in laboratory under aerobic-to-anaerobic conditions at 25°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. 800 / éoo O A- O 0‘) E \ V E \ O “a O I I I O 0 10 25 180 sb so DAYS OF DECOMPOSITION : esATP = =ETS Appendix Figure 242. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 25°C. ATP content (pg ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O O O m f 1'11”.” I \ / .m 8- V 9: I -§ 2 CE 0 LU NI 8 c5 Nu O I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION rs :ATP r :ETS Appendix Figure 243. Decay oi Najas ilexilis in laboratory under aerobic-to—anaerobic conditions at 25°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O O O In \ I m I ‘\ / w 3 1 “° 0. O 0) t- 'q- i— C! O I.“ N. O PO 0 (U fi'M ./ O —I I I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION = :ATP — — —oETS Appendix Figure 244. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerabic conditions at 25°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. 800 WWfi __ ____ --—... v \ / \ F8 3- V \ a \ 3 a O \o v N- O O O"l 'N O f I fl I O 0 IO 25 180 : :ATP Appendix Figure 245. 50 90 DAYS OF DECOMPOSITION ~——— -———-——~ETs Decay oi Nuphar variegatum ETS in laboratory under aerobic-to-anaerobic conditions at 25°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. 50 800 ‘\ ~<::’ /// / 400 600 2: - 23 Cl: I.“ g. \. c: c: 0. g. 'N O I r I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION e :ATP -— — —~ETS Appendix Figure 246. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 25°C. ATP content (”9 ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O a s - s s I \ I \ O V’" \ \ 8 / \.'P O .J \ a / 3 C a. \ O O EH 'nI O I I IF :0 0 10 25 50 90 180 DAYS OF DECOMPOSITION : =ATP ~—————-ETS Appendix Figure 247. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 25°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash—iree dry weight oi plant tissue. 50 800 4. nun-II." 600 ATP 400 ETS o / / n F.‘ \'-—- “-— / -..____ W, O I I I I TO 0 IO 25 50 90 ' 180 DQYS OF DECOMPOSITION : =ATP = 2:513 Appendix Figure 248. Decay oi Scirpus acutus in laboratory under aerobic conditions at 25°C. ATP content (Do ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. ETS 1 so 600 800 ATP 400 ETS 200 O I I I I O 0 10 25 50 90 180 OQYS OF DECOMPOSITION : :ATP —— — -—oETS Appendix Figure 249. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 25°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. 50 800 4. soo ATP 400 ETS 200 0 so so 180 DAYS OF DECOMPOSITION s :ATP — —— -—-oETS Appendix Figure 250. Decay oi Najas ilexilis in laboratory under aerobic conditions at 25°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. 50 800 8-1 3 b (.0 O O. om P- - P- c: ~ =ETS Appendix Figure 251. Decay oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 25°C. ATP content (Do ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O O O O O (D O 0.. Om 5E q'Ei O O N O I I I I O 0 IO 25 '50 90 180 DQYS OF DECOMPOSITION : :ATP = :ETS Appendix Figure 252. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 25°C. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. s 4% 3‘ \ 8 ’(D O 00* \ / O a. / .2 G O / cu' \ ,/" \z / \ / / '8 24 / N A! /_. O I W I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION :* eenTP ———--——— ——~ETS Appendix Figure 253. Decay oi Scirpus acutus in Lawrence Lake littoral zone during spring and summer. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O O O I!) m e- 3 “‘0 g. P 8 l- 'v c:<> Nd 5‘ T_ "—T'c> O <3. 'Gl O I I I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION s: =ATP re + ml 0. 53 a w <> m. c> c> n: g. /\ ' / \ o ' ' '7 1 o 10 25 so so 180 ° DAYS OF DECOMPOSITION :+ :ATP = =ETS Appendix Figure 255. Decay oi Noios ilexilis in Lawrence Lake littoral zone during spring and summer. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O O O ID O O .- is ‘0 O ma . \ s l- 'v a: o \ N. O O <3. "U \ O I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION : cATP : =ETS Appendix Figure 256. Decay oi Myriophyllum heterophyllum in Lawrence Lake littoral zone during spring and summer. ATP content (pg ATP) and ETS activity (relative absorbance units) per g ash—iree dry weight oi plant tissue. ETS ETS 0 800 In-F-j' A 2.; \ g 8.1 \ o g »8 L / \ \ \ H‘ / \ / / O I i I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION :: =ATP ~——--—-—'-—~ETS Appendix Figure 257. Decay oi Nuphar variegatum in Lawrence Lake littoral zone during spring and summer. ATP content (pg ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O O 00 O O ’(O a. $3 0- Ma- C O O 'N O I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION = ssnTP = SETS Appendix Figure 258. Decay oi Scirpus acutus in Lawrence Lake littoral zone during iall and winter. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. ETS ETS 50 800 O.I O " <3 ’(0 8- o O. P- _c>gg v (I 0 DJ m. ”—— A“ \ / -'-I-I- -—-_. “— __ _ . 8 o / .N H. I I 5 O I I O 10 as o 9 180° DAYS OF DECOMPOSITION : =ATP ~— —— —-ETS Appendix Figure 259. Decay oi Scirpus subterminalis in Lawrence Lake littoral zone during iall and winter. ATP content (”9 ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O O O ID (I) 8- 3 ND 5; 9: .§ 93 CI: O NJ N. O O o Pm v-o“ _ '4:— -—-— —-— -—- —"“"-=-—. O I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION : imp .__ — —-I-:Ts Appendix Figure 260. Decay oi Najas ilexilis in Lawrence Lake littoral zone during iall and winter. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. c: c> m 8 on c: v- _c, (O 8.. O 9'- /\ n8 {’3 G O N tu' /' \\\ \ o -‘_-“ 4% 2‘ / \ A - \ :2 O I I I I O 0 IO 25 50 90 180 DAYS OF DECOMPOSITION ? =ATP 0-— -— —-°ETS Appendix Figure 261. Decay oi Myriophyllum heterophyllum in Lawrence Lake littoral zone during iall and winter. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O O O ID a) 8- g (O 3% a. 8 m P- mei— CI: O LIJ NI 8 c: "U H. O I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION f 4ATP 0— —— —-°ETS Appendix Figure 262. Decay oi Nuphar variegatum in Lawrence Lake littoral zone during iall and winter. ATP content (pg ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O 3 - i 8 o \ g“ g% S- \- O & \ .gfe Clio. \ m N O 0 \‘xx b8 g. N “'3 O I " ' I I O 0 10 25 50 90 ISO DAYS OF DECOMPOSITION : :STP ———---— -—~ETS Appendix Figure 263. Decay oi Scirpus acutus in Lawrence Lake pelagial zone during iall and winter. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. O O O In (D 84 8 HO O m. .0.- / f" .§ 3 LU \\\_',,. E; c5 ' "U H /\\ O I I I I O 0 10 25 5 90 180 0 DAYS OF DECOMPOSITION es SATP = SETS Appendix Figure 264. Decay oi Scirpus subterminalis in Lawrence Lake pelagial zone during iall and winter. ATP content (n9 ATP) and ETS activity (relative absorbance units) per g ash—iree dry weight oi plant tissue. 50 800 8- g ’(0 8. °- 8 l- Pv- “<> Nd O O c5 nu M.,—x h — —— -—. O I j I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION ‘ s++ — N" O. M DN 0 —I I I F o 0 10 25 50 90 180 DAYS OF DECOMPOSITION :— =ATP .._._ — ——oETS Appendix Figure 269. Decay oi Scirpus subterminalis in Nintergreen Lake littoral zone during iall and winter. ATP content (pg ATP) and ETS activity (relative absorbance units) per g ash—iree dry weight oi plant tissue. O O O ID in 8- g ’(0 a; 9: .§ Cl:<> N. F O O O “’V 'N v-O‘ .--— __ _ _ __ __. O I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION . :ATP —— — -—oETS Appendix Figure 270. Decay oi Najas ilexilis in Nintergreen Lake littoral zone during iall and winter. ATP content (ug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. ETS ETS O 53 E; O v. O :3“ ‘//\\\- c: .I— ' ~ -—~—. Dv .- ‘:<> 1/ u: N. O O O I'(IJ ". O I 1 I O 0 IO 25 180 so so DAYS OF DECOMPOSITION :2 :ATP s~ :ETS Appendix Figure 271. Decay oi Myriophyllum heterophyllum in Nintergreen Lake littoral zone during iall and winter. ATP content (pg ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. <> c: c: In ,P a) /// 8- / g /// no :3. f\ /,/ a / \ / .892 °:c> \/’ q'us cO- // O O <3. y 4—4 "U " ’//’/”,,r O I F I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION e. sATP ~——--——— ——~ETS Appendix Figure 272. Decay oi Nuphar variegatum in Nintergreen Lake littoral zone during ial] and winter. ATP content tug ATP) and ETS activity (relative absorbance units) per g ash-iree dry weight oi plant tissue. 60 in O l---l.t).l ”q- EV' *h-—_- """"—'---—-o g m2 °-<> ,__ ‘T‘ 22 .m 8 O 0! F! "V 5 E (KID oo—-—--._.-._________. H an % -~ 0 I I I O 0 IO 25 50 90 180 DAYS OF DECOMPOSITION L :CgN e—————o'/,C o—--——-—-o°/,N Appendix Figure 273. Decay oi Scirpus acutus in laboratory under aerobic-to-anaerobic conditions at 10°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 ID ° L Em- I luv 32 z: u: ________ ________._‘-o> 0.0 2"— p.2— .0) :3 F’ tr H —:'N 5 -______________ E MID "" H 2: .... O O 50 90 180 DAYS OF DECOMPOSITION : cogN : :ZC o————-——-———o‘/,N Appendix Figure 274. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 10°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 5 "V 45 5 I t I [I i It PERCENT N C:N RATIO. PERCENT C 30 "N ID H OI I 1 I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION ; :CgN o-————0°/.C 0---—-—°./oN Appendix Figure 275. Decay oi Najas ilexilis in laboratory under aerobic-to-anaerobic conditions at 10°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 in O i—ln. ”q- EV 3; :2 BO “’5 .TD‘ In O __-a——-“'--'—. g H _________,.._—-o---‘" ___..——o—"-.DN «In ZIE. ‘\~/ - - '_F. O OI I I I I O 010 25 50 90 180 DAYS OF DECOMPOSITION A: :CIN : :ZC I———-—-e°/,N Appendix Figure 276. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerobic conditions at 10°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 in ’%—-———-—-—O—-_——-——-—— --0 ° / l-ln. I ‘__.'V’ g* g” 4~~flfl Z {5 I\.v<7( ”GDP. 0'8: I E o “,4 O 53 I nuifi E; (L mm E" :~ 0 'fi 2 OI I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION .fi FCIN .—————o°/,c o-—--—-—°./oN Appendix Figure 277. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 10°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O . O ID 0 I-In‘ w 5" _, g A—u—_____. ”ca—fl; z u: ,,/’ “-"-“‘ ND,_ “:84 \/ E. 90 O - Lug : W‘ LIJ E /.——-—_--O-"—--—---—- 0.. M2 r’\‘/’ E I ”—0 O OI I I I I O 0 IO 25 50 90 180 DAYS OF DECOMPOSITION : :CgN r :'/,C o———--—o°/,N Appendix Figure 278. in laboratory under anaerobic conditions at 10°C. Decay oi Scirpus subterminalis Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 in O PU). ”V a? O 3‘: -m °-<> om. O + -—-..-.—- : \A—‘rz-m-—:—--—-—-- MW 0: ‘V’ MID A~ s" v T as" O OI I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION : =CzN ~—-——--°/.c -—-—-—°°/-N Appendix Figure 279. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 10°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O (D ID 0 I'm ”V Ev N My” -—. o w m w ”m °-<> .O)‘ E: -“. 5? --—'—'_"_° N m£.\ ,"/T Z “w, 'H O O I I II 1 O 010 25 50 90 180 DAYS OF DECOMPOSITION r flC8N °——————"/°C ‘—"‘—" 'y'N Appendix Figure 280. Decay oi Scirpus acutus in laboratory under aerobic conditions at 10°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. PERCENT N PERCENT N 60 if) Q i-m ”q- E“ O m I.” °-<> .m O H '— C MU) EH 0 OI I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION : 4C3N o——-————o°/,C 0-—-—--—0./,N Appendix Figure 281. in laboratory under aerobic conditions at 10°C. Decay oi Scirpus subterminalis Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O ‘D ID 0 Es. v LIJ O M LIJ ”(0 0.8 0—-—-.______-_-.~~ o" 0-——-o———7/-‘——-——-—o—-—:':.=_ - :__.. i2 z N O KID EH v__ c #"H O OI I I I I'O 0 IO 25 50 90 180 DAYS OF DECOMPOSITION : ecm = ='/.C o—-——-——»°/.N Appendix Figure 282. Decay oi Najas ilexilis in laboratory under aerobic conditions at 10°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. PERCENT N PERCENT N 60 in O l-ln ”q- E" O E 0 ”m £34 o—‘fi’" “-~---“” :5 _.¢:1___. - .___ ____. E V7 -~ I mm E" s~~ O - T' - OI I I I O 0 IO 25 50 90 180 . DAYS OF DECOMPOSITION 5 :CgN % :ZC o——-———-—O./,N Appendix Figure 283. in laboratory under aerobic conditions at 10°C. Decay oi Myriophyllum heterophyllum Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O (0 ID 0 /s EQ- ' \‘\ ....- "W Lu / s ’#-#- 2 \ ,,,,.. "T' “J \ “’o'm 0'8. Q/ ; \x.#‘____,..——— 5% P\‘“’E‘. Lm .- CI our). EH\_—_\ ”H c: - *— ‘ T I I I O 0 ID 25 50 90 180 DAYS OF DECOMPOSITION r PCIN : :ZC o—————-———-o°/,N Appendix Figure 284. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 10°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. PERCENT N PERCENT N 60 in O I-ln "' E." 0.0 5 am 8 5’ tr H Fm E E “I”.l ‘95" ”H O O I r I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION ; =C:N = 4x0 -—--—-——o'/.N Appendix Figure 285. Decay oi Scirpus ocutus in laboratory under aerobic-to-anaerobic conditions at 25°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O (0 ID 0 P- “V 2 DJ 32 2: U1 ”('0 0- E ' '6’ c: :2 H ”W E 33 Of. IE .4 O OI I I I I O 0 IO 25 50 90 180 DAYS OF DECOMPOSITION : :CgN : :‘l, C o————--—o'/, N Appendix Figure 286. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 25°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 5 O f-lnd 'e- EV 32 2: In I "N 'm 0. ”‘5: ’- ‘8“‘4 K“ "—4-. E C) I ~.\~__:::::==~._=;:::::' c: H / ~..~EI E; a. MID EH r 5 {- A'I-I 0 WV OI I I I I o O 10 25 50 90 180 DAYS OF DECOMPOSITION :_ ;C:N o—————0°/.C 0—-—-—°./oN Appendix Figure 287. Decay oi Nojos ilexilis in laboratory under aerobic—to-anaerobic conditions at 25°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O (D [D O l-m Pv- EV 82 . z 3.’ ,/ \ ~m,_ .8i / x... 5 Cl: Oh. MID E" - A PM 0 OF I F I I O 010 25 50 90 180 DAYS OF DECOMPOSITION :77 ”PC8N E =% C *--"——“"—*x N Appendix Figure 288. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anaerobic conditions at 25°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 5 ' ‘\. ,”‘~ 0 / ~/ ~\ :z-utg :\/'P’——~\:———-—-——'~—'"—_’:v “-c> ' 0,5? .m 8 O M hm“ 33 EI-Oa\ A ; E :F. O ..—— O I I I I O 010 25 50 90 180 DAYS OF DECOMPOSITION :# FCIN I———-—I°/,C o——-—-———o°/,N Appendix Figure 289. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 25°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 5 0 t-m. I'v- EV lg” \ \ "DZ 9'. ~ ”#.~-—-—-_-—-.. g |- l ‘\.—f" mm Cl: / __ —s 0' “m \ \; -: Z" i." O OI I I I I O 0 IO 25 5O 90 ISO DAYS OF DECOMPOSITION : =C:N .2 :zc o-—-—-—.°/.N Appendix Figure 290. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 25°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 in L) . T—In ”v- EV E .,,= “S- -—-. E . -u—fl"- ”N.,..- ‘—-. 2 ‘¢#A~\-w-flo—P’fl’fl .mg L. ‘ ‘~*—--———-——- ———--—--——~ In a 0.. can: H a 'f t ‘r -.'-. c) _s OI I I I I O O 10 25 50 90 180 DAYS OF DECOMPOSITION : :CgN : ;'/,C o———-—I'/,N Appendix Figure 291. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 25°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. <3 (p c: E? u: fig :2 “S E o‘ 2 ”‘ In F’ a. a: azug E" I E., (J O I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION : fiC;N % 12C o———-—-—o'/.N Appendix Figure 292. Decay oi Scirpus acutus in laboratory under aerobic conditions at 25°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 in O i-u) by- El" 0 as 1.. °-<> .09 2 “~'—.¢O———.__ hm .- \——-—-—-—o~__~ hh—o a ‘5... mm + HM a" 4 ~—. 0 O I I I I ‘0 0 10 25 50 90 180 DAYS OF DECOMPOSITION : :CzN 0-——-—°'/.C *—-—'——°'/'N Appendix Figure 293. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 25°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O - (0 ID 0 l-m. iv- EV 8 ’Nu llJ \ hm 0.0-If".- ‘ “fl“ om. \ #:J’K-:M_ O 5" tug...“ “In. H a“ ”N I- 4 ”*0 Cl: (KID. _4 E... L/ —; v." O O I I I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION ; {C:N : 47, C o--—-—---—o'/, N Appendix Figure 294. Decay oi Najas ilexilis in laboratory under aerobic conditions at 25°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. PERCENT N PERCENT N 60 in O F-u) -q' a? 32 w an“. -w’fiikfi pm “‘8. ’ "‘"“"" . ‘“~-.... 0. ’5“. if “4“... r: w “Ohm G fill).I H E k k ,,_, c9 ' ; ~ ' O I I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION e =CzN ~————-'/.c o-—-—-—-o'/.N Appendix Figure 295. in laboratory under aerobic conditions at 25°C. Decay oi Myriophyllum heterophyllum Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O ‘9 l0 0 "V E8. [\s f 8 f‘}\ /'/" LIJ J \\ ,a”, ..,.—--""""'°"('0 0.8 \‘u. - ..-—--I""" g . '- N G “ID §H v A 7 A ___;"I-O 0 CI I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION :~ ~4C3N > :2 C «—---——--—~Z N Appendix Figure 296. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 25°C. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. PERCENT N PERCENT N 60 45 C:N RATIO. PERCENT C 30 .‘2- \ ..—»—- O.\.’#..O—‘"- b O I I I I O 10 25 SO 90 180 DQYS OF DECOMPOSITION :1 :CgN o———'/,c o—-——-—o’/,N Appendix Figure 297. Decay oi Scirpus acutus in Lawrence Lake littoral zone during spring and summer. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 C:N RATIO. PERCENT C DAYS OF DECOMPOSITION :— :CzN = :2 C *—"'—"'——*x N Appendix Figure 298. Decay oi Scirpus subterminalis in Lawrence Lake littoral zone during spring and summer. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O I I I o 0 IO 25 50 90 180 F! O PERCENT N PERCENT N 60 ID 0 l-m. "q- EV g .m2 mod/M‘\ E .m »\ \I- 8 O / ———_._.____._________ a: H .. “M.=.—-—-——____PN E -/ \- - :11 “In. ”H...“ I". -~. a ----.-.__.-_.._, o o I I I o 0 10 25 50 180 DAYS OF DECOMPOSITION : cC:N 3 JAG 0—-—-—../0N Appendix Figure 299. Decay oi Najas ilexilis in Lawrence Lake littoral zone during spring and summer. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio at plant tissue. O (D in O i-m. ”v EV F., .m2 0.8% g a /°~‘- O o \ / ~- EE """"'--*—.. __::4=_‘fnl§§ “I”. "'-._.~ EH \-‘—--~H O I I I I ”o 0 10 25 50 180 DAYS OF DECOMPOSITION = =c.~ = ='/.c -—-——-—~°/.N Appendix Figure 300. Decay oi Myriophyllum heterophyllum in Lawrence Lake littoral zone during spring and summer. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 5 Q l-u) "q- 2?“ fig ‘//"’\\ w \VI\ \ '60 0'0 \ h—h-‘T‘x‘ 6m.\ \.-—-"*\ \‘x H ’ s\~ \\ Pm '— Ny- T" C! - ~--— mm.’\/\/ W~- H a - o O I r I I O 010 25 50 90 180 DAYS OF DECOMPOSITION : :C3N o———-—o'/.C °—"—'_"./°N Appendix Figure 301. Decay oi Nuphar variegatum in Lawrence Lake littoral zone during spring and summer. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O (D in o .- ml ~O—t «ha—g .V O a w ”W °-<> . (0 2 In .- N Cl: m m u-o‘ L a H O O I I r I a O 0 IO 25 50 90 180 DAYS OF DECOMPOSITION : :C3N : :°/, C o——- - — — —o°/, N Appendix Figure 302. Decay oi Scirpus acutus in Lawrence Lake littoral zone during iall and winter. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. PERCENT N PERCENT N 60 in 0 0-10‘ ”V EV O 5 ”fl .m "2.9,./" --_.......——- 9., P- r“. a mm a" '" Ll OI I I I I O 010 25 50 90 180 DAYS OF DECOMPOSITION .2 :cm -————-o'/.c ~—-—-—~%N Appendix Figure 303. Decay oi Scirpus subterminalis in Lawrence Lake littoral zone during iall and winter. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. 60 i0 0 l-tn. ' I'V’ EV O 5 m m8./\.\ é /‘—‘~\~.~---~-~ —‘ IN MID-"‘0‘.“ - “TN H r v a -... 0 O I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION 5 cogN : :7- C 3 " " :7, N Appendix Figure 304. Decay oi Najas ilexilis in Lawrence Lake littoral zone during iall and winter. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. PERCENT N PERCENT N 60 S Q h-u) ‘V' EV O m LU '0') 0.8;‘ ‘,A\ c5 “\~,__~ ____.____ .2 <“‘~- ‘flofl’fl ”N G "T—T “LO-I‘A s. —~ m o O r I I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION : ;C;N o————O'/.C 0—-——-—‘./oN Appendix Figure 305. Decay oi Myriophyllum heterophyllum in Lawrence Lake littoral zone during iall and winter. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O _ (D l0 0 “v 39" ’\ o: / """*¢::~-.._ _ ¢L<>1/ \\' "=”"*-—~ .03 9. . ._ N ¢ “In. Zfi\/_ ‘ b” o O I I I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION . =C:N : =°/.c -—-—--—°'/oN Appendix Figure 306. Decay oi Nuphar variegatum in Lawrence Lake littoral zone during iall and winter. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. PERCENT N PERCENT N 60 5 Q '2 "V “J “1"." 4* ‘ ——-—- —— _ _. O 35 L«u a. £5 . .— N C O! a -- O O I I I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION :. —4C:N - - --'-‘% C ~——--—--——~Z N Appendix Figure 307. Decay oi Scirpus acutus in Lawrence Lake pelagial zone during iall and winter. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O (D ID 0 TV 3 N E! ,/T ~——--———-————.___..__..__. No .:%.——/ 53 \\\> .m‘ o 40‘ H ‘, ”N '- """'—. T‘~ gm/ fiTI“-~ ". 5 -~ 0 O I I I I o 010 25 50 90 180 DAYS OF DECOMPOSITION y 4cm . _.y.c ~—--—-—o’/.N Appendix Figure 312. Decay oi Scirpus acutus in Nintergreen Lake littoral zone during iall and winter. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. PERCENT N PERCENT N 60 5 O l-ID Pv- Ev g ofH-Mfih ,. 8,, -~-——--—.. m .m "K. 0 ‘-~—— :3 / -_--—---_""—"-——~o ”N Cl: - , azu) v— ' z EH ”H 0 CI I I I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION 5 :CgN o———-—¢°/.C 0—-—-—°°/oN Appendix Figure 313. Decay oi Scirpus subterminalis in Wintergreen Lake littoral zone during iall and winter. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. O (D 'ID 0 l-m ”q- LZUV 32 ‘//~ ~.‘_~___‘___.___- ‘“ I/' ’---——-—-——-.£:?2.::::;:: ”at 0'0 / .CD‘ ’g” 2 ' ~ r- r/ “i C «B‘\ E ' : "' O . o I I I I ‘0 O 10 25 50 90 180 DAYS OF DECOMPOSITION : :CgN : 42C ._-—-—../0N Appendix Figure 314. Decay oi Najas ilexilis in Nintergreen Lake littoral zone during iall and winter. Carbon and nitrogen, as percent oi total dry weight, and C:N ratio oi plant tissue. PERCENT N PERCENT N o (D in o F-UD "q- EV O ..—-o g -n—fl‘”"—~.‘ hm “-c> .»—-"“‘ ‘5‘D}/$;§= , ...———--——--—-'--"—“"—‘ r: "" CE mm. EHN ; DH o ——3 o I I I o 0 10 25 SO 90 180 DAYS OF DECOMPOSITION : :C:N o———-——-O'/.C .'_"'—""—../0N Appendix Figure 315. in Nintergreen Lake littoral zone during Carbon and nitrogen, as percent oi total C:N ratio oi plant tissue. Decau oi Myriophyllum heterophyllum iall and winter. dry weight, and O (.0 ID 0 ”9”"...“0 km. f/‘\~w-_p—v" ‘~.. ”V E” [KM—w—fl'fifi o a m I Pm “-c> .m a n '— N C “In a“ ;_ = : ”H 0 CI I I I o 0 10 25 50 90 180 DQYS 0F DECOMPOSITION : :CgN o————-—°'/.C ”—‘_-—../°N Appendix Figure 316. in Nintergreen Lake littoral zone during Carbon and nitrogen, as percent oi total C:N ratio oi plant tissue. Decay oi Nuphar variegatum iall and winter. dry weight, and PERCENT N PERCENT N 50 vs in 00 p-V‘ 'V’ Z ‘6’ 9.58- . z a. tug; - 8 Do a: Hm. hm 5 iii 3 22" __————""'—'.'v-¢ 8 al.-u- _A _‘ __A...—--'—"""" I -—-_-I-.-_-—-—-—-—."O 0 10 25 SO 90 180 DAYS OF DECOMPOSITION : <4C3N ~——--———--—~% C ~—---—---*% N Appendix Figure 317. Decau oi Scirpus acutus in laboratoru under aerobic-to-anaerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) luophilized media. O - ID ID 00 h-v‘ 'V’ Z 8 ass. .002 0- E . 8 Do i: Finn Wu 5 E a: I :553 —r*"'"~ '——‘ "“'wa O \.__-_-—--.— I I I I I -_-——-—-—fl'o 0 10 25 50 90 180 DAYS OF DECOMPOSITION :#7 ‘sC3N -—--———'-—*% C ~—---——-———~% N Appendix Figure 318. Decau oi Scirpus subterminalis in laboratoru under aerobic-to-anaerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 pm) lgophilized media. 50 f ID 00 h-V” 'V’ 2 DJ ég- - z a. “’5 - 8 C>c> (2 H041 ”N E 33 0: as e/ fiN—m'fi 0 0r . :“'—'_4-F=H-¥“'“ “‘"”’"'—-—. o 0 10 25 50 90 180 DAYS OF DECOMPOSITION _% PCIN ~———————o°/,C .—-—-—_../0N Appendix Figure 319. Decau oi Najas ilexilis in laboratoru under aerobic-to-anaerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) luophilized media. 0 ID ID 00 h-v“ ’V' z 3 9.38 «.2 0- E ' 8 Do in m EN NE a A ——-—O 53 “z“ ‘ z —— .._, Q \O-c—-_____-.—-—-—-____. OI I I 1 I o 0 10 25 50 9 180 DAYS OF DECOMPOSITION : flogN : CZC 0—-—-—‘°./0N Appendix Figure 320. Decau oi Myriophyllum heterophyllum in laboratoru under aerobic-to-anaerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 pm) luophilized media. 50 T f in 00 I-V' her 2 '6’ 58- - z a. ing; . LU 28 ..____._ ng E3 ”H O \ ‘¥——_-___..__-___,_________. OI I I I I o 0 10 25 50 180 DAYS OF DECOMPOSITION 3 4cm .___—_.y.c -—-——---°/.N Appendix Figure 321. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue at iiltered (pore size 0.2 um) lyophilized media. 0 ID in 00 h-v‘ “v Z ‘6‘ fig- .03- 0- '2' - 8 (3:) a: ”N. ”N 5 E M E3 ...__..._._——-—-—-*—- ————-~.. 0 #‘fl—‘bfi‘fi— \-——o———-—-—¢""- -“‘-'—-—-—_. OI I I I ”O 010 25 50 9 180 DAYS OF DECOMPOSITION : :CgN e————o°/.C 0-—-—'—°./oN Appendix Figure 322. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. $0 ' in 00 g—v‘ Mr 2 I.“ O 58- we 0. EEO-I i- h»“‘ “I g Mfiflfl-‘hh—a E2 # .Pv-o O o. ' '-~-_'""—’—"—-——1—1a=a—_J.° 0 10 25 50 90 180 DAYS OF DECOMPOSITION :_ 4C;N o————-—O'/.C .——-—-——../0N Appendix Figure 323. Decay oi Myriophyllum heterophyllum in laboratory under anaerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. to O l- by- Z I.l.l O O: l.l.l ”m 0.. g . ._ OJ Cl: 0: E _.__...___ p... 0 ‘.———-~ 0“.- —-—' ———-I _.—_ - —: 5'0 9'0 180 DAYS OF DECOMPOSITION :_ 403N r :%C O-—-_"—../0N Appendix Figure 324. Decay oi Scirpus acutus in laboratory under aerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. PERCENT N PERCENT N 50 - in "c> h-V‘ 'v- § 353. . z a. ing; ,5 8 C’ a: H N ”N a a: a: . a 3 -~ c) O? I I no 0 10 25 50 90 180 DAYS OF DECOMPOSITION % =CxN '———'°'/vc ""’_‘—"'/°N Appendix Figure 325. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. <3 - ID ID "<> .— V‘ f? :z ‘8 5. s- -. z a "z' . L 8 c: «r "i tn 5 E a: 7.: ~~ c) I I I O O 10 25 SO 9 180 DAYS OF DECOMPOSITION : ~403N : 47, C o—- - ———o°/, N Appendix Figure 326. Decay oi Najas ilexilis in laboratory under aerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. 50 U) 0 O .— V‘ "V Z LIJ O 35 8- ma 0.. g" o ._ N "N (I: a: e 3 " M O ——__2 01 O 0 50 90 180 DAYS OF DECOMPOSITION - sC:N - - --'-*z C ”—"‘--"'—‘Z N Appendix Figure 327. Decay oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 pm) lyophilized media. 50 in OOJ b g—V’ v 2 LL! 0 MO lucn' no 0. 93° . h-“l ‘“ 5 A a2 \ ”H OI I I I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION :_ PCSN ._____.'/.c _-_‘—.ZN Appendix Figure 328. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 10°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. PERCENT N PERCENT N 50 in O O t- ?” Fu- 2 ‘6’ 0- ’2' ~ 8 O o a: p. m ”m E E! a: a 3 ~— 0 o I I O O 10 25 50 90 180 DAYS OF DECOMPOSITION : :CgN o-— —— -—O'/. C .—-_-—../o N Appendix Figure 329. Decay oi Scirpus acutus in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. 50 ID 0 O '— V‘ "V Z 8 as 8« m. z 0- '2 ' ‘6‘ EEEI *nlfii c O. O! E 2 ”—0 Q I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION ; ¢C3N : :7. C *— - -— - —'*./o N Appendix Figure 330. Decay oi Scirpus subterminalis in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. 50 5 00d i—v .v 2 8 358- «.2 0' '2 . 3 O __. :38? *— “nag? &. ’ N zzc> .r” \\‘. «H N ____...H 0 \~_————""——"' \ -~--—n‘—_—__.—--—-—-—-—--O OI r I I I o 010 25 50 90 180 DAYS OF DECOMPOSITION : ;CIN ————O./,C o————-——.°/.N Appendix Figure 331. Decay oi Najas ilexilis in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. 0 ID ID 00 i—V‘ ”v z 3 5.8- «.2 ‘L '2 ' ‘6‘ Egan . 1: EN N33 “0 .—-o-"“"""-.\ EH ~.. 0 (As\’/o--—""—' OI I 1 fl I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION ; ;C3N : 4°], C ‘—-—"_../o N Appendix Figure 332. Decay oi Myriophyllum heterophyllum in laboratory under aerobic-to-anoerobic conditions at 25°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. ID in 00 I-V iv 2 8 $8 - z a. (0!; . IJJ ea mg 22 // “\. n. a: \ '_ T as F\ \\ .———--'—"'.'H o I \ /’h~--"'-—:.:__:-:—-——--—-"—’—. i/ ' 0' I I I I o 010 25 50 90 180 DAYS OF DECOMPOSITION ? ccsN ~——-———o°/.c ~—--—-—-o‘/.N Appendix Figure 333. Decay oi Nuphar variegatum in laboratory under aerobic-to-anaerobic conditions at 25°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. O to ID 00 h—V' *v 2 3 fig‘ 'mz 0- E . 3 Do _‘ m HN‘ - N 5 z 33 a: a3 s — —--°~~ O .2 - — -——--—--o OI I I I I O 0 10 25 50 90 180 DAYS OF DECOMPOSITION % 403N : :7, C .—'-—-‘_'../o N Appendix Figure 334. Decay oi Scirpus subterminalis in laboratory under anaerobic conditions at 25°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. 50 in 00 l—v' ”v z LU 0 53.. m 0. 6° - ‘2‘“. ‘\\\.PN c m as %~——____.___.TH ‘3 ,_/--~-—o———-______._______,..__--—--—--o OI I I I o 0 10 25 50 90 180 DAYS OF DECOMPOSITION : =C:N °-———-‘°/-C """'—"—"7'N Appendix Figure 335. in laboratory under anaerobic conditions at 25°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. Decay oi Myriophyllum heterophyllum 0 ID ID 00 p—V‘ ”V 5 c) ”\x 5.8- / ~ .., 0. I \\ ég‘ / \\ hm / \ z:c’i. ~ ~.. (SI-0f ‘ ”#74. h _ %. \----/ \ OI I I I I O 0 10 25 50 9 180 DAYS OF DECOMPOSITION L 4cm ..__._—.y.c ~—-—-—~'/.N Appendix Figure 336. Decay oi Scirpus acutus in laboratory under aerobic conditions at 25°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 pm) lyophilized media. PERCENT N PERCENT N 50 5 o O p.v" ‘v- z 8 mo mm‘ .0, 0. Sign .— C a: ggfi O 50 90 DAYS OF DECOMPOSITION : ‘nN —-————o°/,C o——--—-—o°/,N Appendix Figure 337. Decay oi Scirpus subterminalis in laboratory under aerobic conditions at 25°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. 8 .o O y—S‘ N- 2 U1 8o ”(OJ ”('0 Q. §8i m C (z 553 .___.. _____.--~ 0 T—h—T—I—‘T—I' \o-____._-____-_.___--_-—_____. <> fb éE so Ob 180 DAYS OF DECOMPOSITION : :CIN o—————O'/.C 0—-—-—‘./0N Appendix Figure 338. Decay oi Najas ilexilis in laboratory under aerobic conditions at 25°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. PERCENT N PERCENT N 50 S O I-V‘ ”q- 2 [LI 0 ase- m, 0. saga. cu a.“ v- E ‘ / \-N~~ 1: I “‘--—..___ 22 . -‘-~‘~~~bfl (3 Pi ~'~~o———--——-- t _____=__ —: I I I I I O O 10 25 50 90 180 DAYS OF DECOMPOSITION r =CzN = sex C ~—---——--—~% N Appendix Figure 339. Decay oi Myriophyllum heterophyllum in laboratory under aerobic conditions at 25° C. Percent carbon and nitrogen and C: N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. 50 m 00 I. l-V' q- 2 UJ O a: LU m 0. a '— 0.1 CI: m 2 ”fl 0 50 90 DAYS OF DECOMPOSITION e =C:N .2 ——o°/.c ~—-—-—-°/oN Appendix Figure 340. Decay oi Nuphar variegatum in laboratory under aerobic conditions at 25°C. Percent carbon and nitrogen and C:N ratio oi residue oi iiltered (pore size 0.2 um) lyophilized media. PERCENT N PERCENT N CH GAN STATE UNIV. LIBRARIES 32lllgll Ill 0ll llll lll lllllllllll