m m. . NH,AV . . O. H m M 0 M .0 .w... pa . . _ n .. . ‘ . _ u‘ -..—.a.u - v”- w w w m m u u “ ,. . w LMWS . W . . These 5,. mom e . .1 5.2.5.? 2 $3., .....M$V£,...m&m% I! ‘3‘. w , .r. u\: :0. f 9:... J: 5. 19:4. . .1 ll! “' \\\\\\\\\\\\\\\\\\\\\\\\\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ 3 1293 10454 3099 LIBRARY " Michigan State UniverSIW if _ ”12‘0"” L“ ' This is to certify that the thesis entitled Role of Ca lcium Carbonate Prec ipitat ion in Lake Metabol ism presented by W. Sedgefield White has been accepted towards fulfillment of the requirements for __JEh‘.D..__degree in _Bgtéfly_ 24.14,wa Major pressor Robert G. Wetzel Date n worm! 0-7639 - \ V' anemone "MB 8: SONS' 800K BlNDERY INC. mam, BiNoEBs .i _-. _— .s afllfll- ABSTRACT ROLE OF CALCIUM CARBONATE PRECIPITATION IN LAKE METABOLISM By W. Sedgefield White During a two year period analyses were made every other week on seston collected at three depths in a small hardawater lake in south- ‘western MiChigan. The seston was analyzed for total dry weight, organic material, calcium carbonate, and ash content. During the second year seasonal changes in sestonic particulate organic carbon, Kjeldahl nitrogen, and total phosphorus were assayed. Organic material and ash content of the seston was similar both years, but the calcium carbonate content was five times greater in the second year than in the first. The dissimilarity in calcium carbonate precipitation between the two years was related to degree of vernal circulation and calcium ion concentration in the water column.when the ice broke up. During the study an improved sediment trap was designed and constructed. The trap had replicated, discrete upper and lower sec- tions, which permitted correction for attached and non-sedimenting matter. Investigation of calcium ion concentration by flame atomic absorption and a calcium ion electrode revealed an average of 36.7 mg 1'1 of colloidal calcium was suspended in the lake during 1973. ‘ \ W. Sedgefield White Measurements on total phosphorus content in the seston showed there was a marked displacement of phosphorus out of the epilimnion into the metalimnion during July and August. The dis- placement of phosphorus, among other factors, stimulated algal growth in the metalimnion. Laboratory experiments suggested the availability of iron and vitamin 312 to algae were related to the precipitation of calcium carbonate in hard-water lakes. Iron was not adsorbed directly onto particulate calcium carbonate; instead, the availability of iron may be regulated as calcium carbonate precipitates natural Chelator compounds from the trophogenic zone. In contrast, a significant proportion of available vitamin B12 was removed in association with the precipitating calcium carbonate. ROLE OF CALCIUM CARBONATE PRECIPITATION IN LAKE METABOLISM By W. Sedgefield White A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Botany and Plant Pathology 1974 AC KNOWLE DGMENTS I thank my committee, Dr. Robert G. Wetzel (Chairman), Dr. Boyd G. Ellis, Dr. Brian Moss, and Dr. Stephen N. Stephenson fOr their understanding and constructive advice during my study and researdh. I owe special thanks to Dr. Wetzel for providing an out- standing field and laboratory experience during a summer Limnology course that stimulated my initial interest in this field. I sincerely appreciate the time, encouragement, criticism, and excellent advice Dr. wetzel generously provided during my program. Dr. Ellis willingly gave constructive advice and help in the x-ray diffraction analyses, thermal analysis, surface area determin- ations, and calcium electrode determinations. Stimulating discussions with Dr. R. Anton HOugh, Dr. Midhael J. Klug, Dr. Bruce A. Manny, John Molongoski, Kelton R. Mckinley, Dr..Akira Otsuki, Amelia Ward, and Gordon Godshalk yielded valuable information and suggestions. I thank Karen E. Hogg, Jane Holt, Jayashree Sonnad, and Janet Stralley for their skilled help. The valuable technical advice and help of Madeleine J. Hewitt is gratefully acknowledged. Drs. George H. Lauff and R. G. Wetzel were most helpfhl in making financial support available during my researCh. Financial support was provided by subventions from.ABC grant AT(ll-l)-1599, ii COO-1599, NSF grant GB-15665, and a Graduate Tuition Scholarship from Michigan State University. I wish to recognize the valuable support of my wife, Betty, who has been most understanding and resourceful during this period. iii LIST OF TABLES _ LIST OF Chapter I. II. III. FIGURES INTRODUCTION . . . . TABLE OF CONTENTS A. Sedimentation in Lakes ............. B. Sedimentation of Calcium Carbonate in Hard—Water Lakes ............... C. Description of Lawrence Lake . . . ...... . D. Objectives of Study ............... MATERIALS AND METHODS ............. A. Sampling Schedule. ............... B. Sediment Traps ................ . C. Physicochemical Characterization of Seston. . .................. D. Physicochemical Characterization of Lake Water .................. E. Biological Data ................. ANNUAL VARIATIONS IN SEDIMENTATION AWDNG THE SESTON COMPONENTS .............. A. Introduction .................. B. Total Particulate Seston ....... . . . . . C- Organic Matter . . .............. . D. Calcium Carbonate. . .............. l. Solubility of Calcium Carbonate . ............... 2. X-ray Diffraction Analysis of Seston ................ 3. Calcium Carbonate Content of Seston . . . ............. 4. Causes of Calcium Carbonate Precipitation . . . . .......... iv \)\1 12 19 21 63 69 70 70 5. Supersaturation with Calcium Carbonate . . . . . . . . . . 6. SEM Photographs of Calcite Crystals ........... E. ASH. . . . . ........... IV. SEDIMENIATION OF METABOLICALLY IMPORTANT PARTICULATE MATERIAL FROM THE TROPHOGENIC ZONE . . . . . . . . .......... A. Particulate Organic Carbon . . . . B. Kjeldahl Nitrogen ........ C. Total Phosphorus . . . . . . . . . V. ASSOCIATION OF IRON AND VITAMIN B12 WITH CALCIUM CARBONATE ......... A. Iron Experiments ......... 1. Introduction ......... 2. General Procedures ...... 3. Results . . . . . . . . . . . B. Experiments with B O O O O O O 0 VI. VII. LIST OF REFERENCES , . DISCUSSION , , . , A. B. C. SUWIARY AND CONCLUSIONS, 12 0 I O O O 000000000 1. Introduction. . . ........... 2. General Procedures. . . . . . . . . . . . . 3. Results . . ................ Sedimentation of Seston Components . Significance of Suspended CaCO3, , , Carbon, Nitrogen, and Phosphorus Ratios ..... Page 79 85 94 94 98 101 103 103 103 104 105 107 107 108 110 117 117 120 123 132 135 Table LIST OF TABLES Sedimentation Rate of Total Seston Collected During 1972 - 1974 in Lawrence Lake. Quantity is Expressed as mg m“2 day‘l . . . . . . . . Sedimentation Rates of Components of Seston Collected During 1972 - 1974. Quantity is Expressed as mg m'2 day‘l . ..... Sedimentation Rates of Particulate Organic Carbon (POC), Kjeldahl Nitrogen, and Total PhOSphorus in the Seston of Lawrence Lake During 1973 - 1974. Particulate Organic Carbon and Nitrogen are Expressed as mg mfz day’l. Phosphorus is Expressed as pg mfz day‘1 . . Amount of Iron and Calcium Carbonate Precipitated as pH is Increased . . . . ..... Loss of Vitamin B and Calcium Ion From Lake Water as Ca 03 Precipitated. . . ..... . . . . Interaction Between B and CaCO When the pH was Raised Rapid}? With 0.23M NazCO3 . . . . . Analysis of Variance Table of Data on Vitamin B12 Content in Lake Water.After pH was Raised Rapidly From pH 8.30 to pH 9.50. The Data is Given for Two Concentrations of Vitamin B12. . Analysis of Variance Table of Data on Vitamin B Content on Filters.After the pH was Raised Rapidly from pH 8.30 to pH 9.50. The Data is Given for Two Concentration Levels of Vitamin B 12 12 . . . vi Page 32 33 97 106 111 112 114 115 LIST OF FIGURES Figure l. iMorphometric MBp of Lawrence Lake, Barry County, Michigan. Sediment Traps Were Located at Station A .................... 2. Diagram of Sediment Traps Showing Construction and Method of Attachment ................ 3. Differential Thermal Analysis Curve Showing Decomposition of Seston From the 10 m Sediment Trap in Lawrence Lake. Decomposition Took Place in Air and Arrows Indicate Changes in Recording Resistance .................. 4. Differential Thermal Analysis Curve Showing Decomposition of Sediment From the Lake Bottom in Lawrence Lake. The Decomposition Took Place in Air and Arrows Indicate Changes in Recording Resistance . ...................... 5. Isotherms of Temperature (0C) at Station A in Lawrence Lake, 1972. Opaque Areas at the Surface Represent Ice Cover ....... . ....... 6. Isotherms of Temperature (0C) at Station A in Lawrence Lake, 1973. Opaque Areas at the Surface Represent Ice Cover. . . . . . . . . . ..... 7. Seasonal Variations in Total Dry weight of Seston (g m‘2 day‘ ) Collected in Sediment Traps Suspended at 2, 6, and 10 Meter Depths. Traps Were Located at Station A in Lawrence Lake From 8 January 1972 to 8 January 1973. Bars Equal i S.E. Where no Bars Appear, the S.E. was Less Than the Thickness of the Line ...... 8. Seasonal variations in Total Dry Weight of Seston (g m-Z day‘l) Collected in Sediment Traps Suspended at 2, 6, and 10 Meter Depths. Traps Were Located at Station A in Lawrence Lake From 8 January 1973 to 8 January 1974 ...... vii Page 11 15 17 24 26 29 31 Figure 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. Isopleths of Oxygen Concentration (mg 1'1) at Station A in Lawrence Lake, 1972 ........... Isopleths of Oxygen Concentration (mg 1‘1) at Station A in Lawrence Lake, 1973 ........ Isopleths of Alkalinity (meq 1'1) at Station .A in Lawrence Lake, 1972 ........ . . Isopleths of Alkalinity (meq 1'1) at Station .A in Lawrence Lake, 1973 .............. Isopleths of pH at Station A in Lawrence Lake, 1972. . . . . . . . . . . . . ........... Isopleths of pH at Station A in Lawrence Lake, 1973. . . ...................... ISOpIeths of Ca2+ Concentration (mg 1'1) at Station A in Lawrence Lake, 1972. ........ IsoPleths of Ca2+ Concentration (mg 1-1) at Station A in Lawrence Lake, 1973 .......... Relative Percentage Composition of Calcium Carbonate, Organic Matter, and Ash in Seston Collected From 8 January 1972 to 8 January 1974 in Lawrence Lake ................... Scanning B1ectron.Micrographs of Seston Caught in Sediment Traps During August 1973 and Filtered onto 8 u Nuclepore Filters. a: Material Collected in Sediment Traps Suspended in the Epilimmion, 2 Meters (ZOOX). b: Material Collected in Sediment'Traps SuSpended in the Metalimnion, 6 Meters (ZOOX) . . . . Scanning Electron Micrographs of Seston Collected During August 1973. a: Seston Collected From 10 Meters Showing the Fine Particulate Material and Gelatinous Organic .Matrix (SOOX). b: Enlargement of Detritus Showing Crystals of Calcite and Fragments of Diatom Frustules in an Organic.Matrix (SOOOX) . . . . viii Page 37 39 41 45 47 49 51 53 56 58 Figure 20. 21. 22. 23. 24. 25. 26. 27. Seasonal Changss in the Organic Component of Seston (g m day‘l) Collected in Traps at 2, 6, and 10 Meter Depths. Traps Were Located at Station A in Lawrence Lake from 8 January 1972 to 8 January 1973. Bars Equal i S.E. The S.E. was Less Than the Thickness of the Line Where No Bars Appear. ........ Seasonal Changes in the Organic Component of Seston (g m 2day 1) Collected in Traps at 2, 6, and 10 Meter Depths. Traps Were Located at Station A in Lawrence Lake From 8 January 1973 to 8 January 1974 ...... ISOpleths of Corrected ChlorOphyll 3 (ug 1’1) at Station A in Lawrence Lake 1972 ...... Isopleths of Corrected ChlorOphyll a (pg 1.1) at Station A in Lawrence Lake 1973 ..... Seasonal Changes in Calcium Carbonate Content of Seston (g m Zday 1) Collected at Station A.in Lawrence Lake. Traps were Located at 2, 6, and 10 Meter Depths From 8 January 1972 to 8 January 1973. Bars Equal+ S. E. Where No Bars Appear the S. E. was Less Than the Thickness of the Line . . . .............. . . Seasonal Changes in Calcium Carbonate Content of Seston (g m 2 day 1) Collected at Station A in Lawrence Lake. Traps were Located at 2,6, and 10 Meter Depths From 8 January 1973 to 8 January 1974.. . . Seasonal variation in Total Phosphorus Content (mg m'2 day‘i) of Seston Collected at Station A in Lawrence Lake. Traps were Located at 2, 6, and 10 Meter Depths From 8 January 1973 to 8 January 1974. ............... Variations in Colloidal Calcium (mg Ca2+ 1‘ Suspended in Lawrence Lake at Station A. Quantity of Suspended Calcium is Given for 2, 6, and 10 Meter Depths . . . . . . . . ...... ix Page 60 62 65 67 72 74 78 81 J... ..I. I .. M Figure 28. 29. 30. 31. 32. 33. 34. 3S. Scanning Electron Micrographs of Material Collected From Lawrence Lake.. a: Calcite Crystals Filtered Onto a 0.4 u Nuclepore Filter From Water Collected at 6 Meters, May 1973 (ZOOOX). b: Seston Collected From 10 Meters Showing Bacteria in the Foreground With Calcite Crystals Embedded in an Organic Matrix in the Background (2000K). . . . ..... Seasonal Variation in Ash Content (g m‘2 day‘l) of Seston Collected at Station A in Lawrence Lake. Traps Were Located at 2, 6, and 10 Meter Depths From 8 January 1972 to 8 January 1973 . Seasonal Variation in Ash Content (g m"2 day'l) of Seston Collected at Station A in Lawrence Lake. Traps Were Located at 2, 6, and 10 Meter Depths From 8 January 1973 to 8 January 1974. Isopleths of 8102 (mg 1'1) at Station A in Lawrence Lake, 1972. . . ..... Isopleths of SiO e(mg 1 l) at Station A in Lawrence L e, 1973. . . . . . . Seasonal Variation in Particulate Organic Carbon (g POC m 2 day l) of Seston Collected at Station A in Lawrence Lake. Traps were Located at 2, 6, and 10 Meter Depths From 8 January 1973 to 8 January 1974.. . . ..... Seasonal Variation in Kjeldahl Nitrogen (g m 2 day i) of Seston Collected at Station A in Lawrence Lake. Traps Were Located at 2,6, and 10 Meter Depths From 8 January 1973 to 8 January 1974.. . . . . . . . . . . . Seasonal Changes in CarbonzNitrogen:Phosphorus Ratios (by weight) of Seston Collected at Station A in Lawrence Lake. Traps were Located at 2, 6, and 10.Meter Depths From 8 January 1973 to 8 January 1974. Particulate Organicl Carbon and Nitrogen are Expressed as daymg m dayl Phosphorus is Expressed as pg m ..... Page 84 87 89 91 93 96 125 Jr'— wm- Aw Figure Page 36. Seasonal Changes in CarbonzNitrogen Ratio (mg m'2 day'l) of Seston Collected at Station A in Lawrence Lake. Traps Were Located at 2, 6, and 10 Meter Depths From 8 January 1973 to 8 January 1974 ...................... 129 37 - Seasonal Changes in CarbonzPhosphorus Ratio by Weight (X10 ) of Seston Collected at Station A in Lawrence Lake. Traps Were Located at 2, 6, and 10 Meter Depths From 8 January 1973 to 8 Janua 1974. Particulate Organic Carbon is Expressed as mg m‘ day‘l; whereas, Phosphorus is Expressed as ug m'2 day 1 ....................... 131 xi a... I. INTRODUCTION A. Sedimentation in Lakes Initial investigations on lake sediments by Heim (1900) stimulated a more detailed consideration of this topic, and a number of studies were undertaken after Nipkow (1920) disclosed and success- fully reconstructed conditions that led to stratified sediments in Zurichsee. These studies have provided valuable information on the physicochemical quality, as well as the quantity of seston reaching the bottom of lakes (Reissinger, 1932; Scott and Miner, 1936; Wilson, 1936; Rossolimo, 1937; Pechlaner, 1956; HOhne and Olrich, 1966; Ludlan, 1967; Heinemann, Rausch and Campbell, 1968; Emery, 1973). Rates of seston mineralization and nutrient release from the sediment has received attention (Mortimer, 1941-1942; Kleerekoper, 1953; Hayes, 1964; among others). Biological investigations of the sedimenting seston and sediment have given attention to both algae (e.g. Conger, 1942; Jarnefelt, 1955; Tutin, 1955) and zooplankton (e.g. Frey, 1960). Although the resulting profusion of ecological information deduced from seston and sediment core analysis has revealed valuable information about past production rates, close study has not been accorded factors controlling contemporary production. In contrast, Thomas (1950, 1951, 1955a, 1955b, 1956) used a specially designed sediment pan to collect and investigate sedimenting / seston during short periods of time. His investigations demonstrated phytoplankton mineralization rates, settling rates of particulate matter, and the removal of nutrients from the trOphogenic zone influenced the productivity of lakes. These studies inferred seston can function in a regulatory manner in the total operation of an aquatic ecosystem. When a detrital food chain was proposed (Odum, 1962, 1963; Odum and de la Cruz, 1963), additional importance of detritus in the structure and function of an ecosystem was implied. Many limnologists were already aware of seasonal variations in the quantity and quality of dissolved and particulate organic detritus in lakes, and studies on seston expressed this awareness (e. g. Lawacz, 1969, 1970; Moss, 1970). The wealth of new information about dissolved and particulate organic detritus in seston prompted an IBP-UNESCO symposium on detritus in Pallanza, Italy during 1971. Although considerable diversity existed among the data presented at this meeting, there was general agreement on two major points. First, there is an important detritus pathway, parallel to the grazing pathway, in which energy from dead animal and plant material is transferred to microorganisms. Second, energy partition in an aquatic ecosystem can be influenced and/or regulated by the detritus component of seston. Sedimentation is the major mechanism for transport of detrital Organic matter; accordingly, sedimentation determines the distribution of metabolism within the aquatic system, and is one method by which the Comrponents of the aquatic ecosystem can be influenced and/or regulated. Sedimentation rates of particular seston components are explored in the present work. The sedimentation of calcium carbonate is especially important here, since it is a major fraction of the inorganic component of seston in hard-water lakes. Detrital organic compounds and metabolically important nutrients in the seston can be absorbed and coprecipitated with calcium carbonate as it precipitates from the trophogenic zone. B. Sedimentation of Calcium Carbonate in Hard-Water Lakes Investigations by Ohle (1934) on hard-water lakes in northern Gemany, have demonstrated that concentrations of calcium and bicarbonate in the epilirmiion exceed what would be anticipated at equilibrium and normal atmospheric partial pressures of carbon dioxide. This apparent supersaturation with calcium carbonate exists in Lawrence Lake, a small hard-water lake of southwestern Michigan, and has been I‘ep<:>rted in other studies as well (Steidtmann, 1935; Brunskill, 1969; Wetzel, 1973). Special significance is assigned to the particulate and Colloidal carbonate when supersaturation exists, since biochemical reactivity and adsorptive capacity is a function of surface area. One "11.151; acknowledge coprecipitation and adsorption both proceed in a ColTlplicated manner; nevertheless, calcium carbonate sedimentation can coprecipitate important nutrients e. g. iron, phosphorus (Otsuki and Wetzel, 1972; Wetzel, 1972) and adsorb dissolved organic compounds e-g. lipids, yellow humic acids, amino acids (Suess, 1968, 1970; Meyers and Quinn, 1971; Wetzel and Allen, 1972; Otsuki and Wetzel, 1973)- Hard-water lakes are well buffered at pH 8.0-8.4 and alkalinity varies between 2 - 5 meq liter-l. Concentrations of metabolically important nutrients such as iron and phosphorus, are markedly low in hard-water lakes; however organic and inorganic nitrogen may occur at high levels (Manny, 1971). Indirect evidence would indicate (Schelske, 1962) that the low levels of naturally occurring chelating agents e.g. dissolved organic matter, in marl lakes may be one factor limiting productivity. Wetzel (1965, 1966a, 1966b, 1968, 1972, 1973) has given evidence that particulate and colloidal calcium carbonate can effec- tively inactivate certain labile organic compounds, reducing bacterial metabolism and subsequently disrupting the regeneration of organic and inorganic material which ultimately results in reduced productivity. The high concentration of calcium carbonate in the sedimenting seston 0f Lawrence Lake (Rich, 1970a; Miller, 1972; Wetzel _e_t_ 31., 1972) Offered the opportunity to investigate the alleged relationship with sedimenting seston, and to determine the temporal sequence in which nutrients are utilized by the phytoplankton and/or precipitated from the trophogenic zone . C. Description of Lawrence Lake Lawrence Lake is situated along the southern boundary of Barry County in southwestern Michigan and is located about 2.1 km east of HiCkory Corners. The local topography that is part of the southern outwash apron 0f the Kalamazoo moraine (Leverett and Taylor, 1915) and the moI‘phometry of the lake basin indicate that Lawrence Lake is a kettle lake. Lawrence Lake is a small (4.96 ha), deep (12.6 m), hard-water -.b . .... .A. . _.s Ff. De .- o ,p. . - \.. lake surromded by a watershed roughly 7 times larger than the surface area of the lake. Glacial deposits upon the outwash apron contain deposits rich in limestone, thus calcium is the predominate cation in the drainage to the lake. TWO small spring-fed brooks and several submerged springs along the shoreline supply drainage to the lake. A single outlet is located in the south by southwest corner of the lake and drains through a marsh into Augusta Creek. Lawrence Lake has a mean depth of 5.89 m, a volume of 292,000 m3, and a shore development of 1.29. An extensive marl bench exists along the littoral zone, and has been dredged in the past for lime kiln and agricultural use (Rich, 1970b). The lake water is well buffered at a pH of 8.0 to 8.5 by the C02 - HCOS- - C032‘ equilibrium system. Divalent cation concentrations are high, especially calcium ion, which varies between 50 to 90 mg liter'l. In contrast, monovalent cation concentrations are very low. The alkalinity ranges from 2 to 5 meq liter‘l, and the specific conductance Varies between 300 and 600 umhos cm'l (25C) . PhytOplankton production rates are moderate to low, indicating the relative oligotrophic state of Lawrence Lake (_c_f_. Wetzel, e_t__ a_1_., 1972). D. Objectives of Study Elementary goals in this study were to establish seasonal Variations in the quantity and precipitation rates of organic matter, Calcimn carbonate, and ash during a two year period. The investigation of calcium carbonate precipitation rates included a determination of Colloidal calcium carbonate, measured by differences between dissolved . 0"‘I'- I ran-6‘. 0‘ POAN‘ ‘ b “be 1‘ e . awn“ udul 1 .A. a W 5‘. :v-u' .H . ...“ N 4. , I), 1‘31. I calcium (ionic) and total calcium. These goals were strengthened by differential thermal analysis, x-ray diffraction, and scanning electron micrographs of the sedimenting seston. Correspondingly, the content of organic matter, calcium carbonate, ash, particulate organic carbon, Kjeldahl nitrogen, and total phosphorus was assayed in the sedimenting seston during the second year to ascertain the dynamics by which metabolically important compounds are removed from the trophogenic zone. A collateral goal in this study was to conduct laboratory e2q1eriments on the association of iron and vitamin B12 with calcium carbonate to corroborate field observations on nutrient interactions with precipitating calcium carbonate. II. MATERIALS AND METHODS A. Sampling Schedule Sedimentation traps were placed at 2, 6, and 10 meter intervals on a cable between an anchor and surface buoy, located at the central depression (Station A) in Lawrence Lake (Figure 1). These depths were chosen since each was located in the epilimnion, metalimnion, and hypolimnion, respectively. All collections were taken biweekly, except for the spring of 1972 and 1973, when collections were made weekly. B. Sediment Traps The sediment traps used in this study are described in detail elsewhere (White and Wetzel, 1973). The collection chambers were made from Schedule 80 polyvinylchloride (PVC) pipe (Figure 2). Upper and lower chambers were formed when each threaded end of the PVC pipe was turned into a PVC coupling, which contained two rubber stoppers inserted between acrylic plastic disks. The suspension rack was made from acrylic plastic, two support bases (Flexaframe Foot, Fisher Sci. Co.), an aluminium support rod, and two Flexaframe hook connectors. The rack was placed upon a support cable by a hook connector attached to the support rod, which firmly presses the support cable against the support rod when it is tightened. The lower spring clip rests on a line clamp attached to the suspension cable. Before the traps were removed from the lake, No. 10 rubber StOppers were inserted into the bottom of each collecting chamber. The .< 533m um R583 203 mass Homegom .cwmafida 33.560 5.8m .984 oucogq mo Ame 352230214 momma mamew} z_MJ<>KMFz_zDthoo hwwu OOn OO~ 0°. 9%. mmwhufi 2495.2 5238 team .33. .2: RN 0mm w¥<4 mozmmcsdj EQSN 93d H 93mm 10 Figure 2.-—Diagram of sediment traps showing construction and method of attachment. 11 Figure 2 :tion 12 water and sediment in the collecting chamber were poured into containers and transported back to the laboratory for analysis. Corrections for attached and non-sedimenting total phosphorus, Kjeldahl nitrogen, particulate organic carbon, and loss on ignition, were made by sub- tracting the quantity in the lower chamber from the quantity contained in the upper chamber. This correction was particularly significant in the total phosphorus and Kjeldahl nitrogen determinations. C. Physicochemical Characterization of Seston The sedimented seston from the traps was filtered onto pre- combusted (525C) glass fiber filters (984 H Reeve Angel) of 0.3-0.5 um porosity (Sheldon, 1972) for all the chemical analyses. Throughout this study, the word seston is used according to Kolkwitz (1912) and includes both living and non-living particulate components. During 1972, sedimenting seston was collected from eadh of four upper and lower chambers of the traps. The total dry weight of seston was determined after filtering the contents of each upper and lower chamber onto individually weighed, precombusted glass fiber filters. The filters were placed into separate precombusted (950°C), weighed combustion boats; dried at 105°C fer 24 hours; cooled under desiccation and then weighed to 1 0.05 mg. Each sample was heated at 550°C for one hour, cooled under desiccation, and reweighed to determine loss on ignition for an estimate of organic weight. Finally, each sample was heated at 950°C for 3 hours, cooled under desiccation, and reweighed to determine the calcium carbonate content from the loss of carbon dioxide. The quantity of calcium carbonate was determined by multi- Plying the carbon dioxide loss by 2.274. The ash content was determined A“. ‘E‘Cr db». are“ iw-U' 13 by subtracting the combined.weights of calcium carbonate and organic matter from the total dry weight of the seston. Ignition temperatures were selected after differential thermal analysis (DTA) was performed on seston collected in the traps and sediment retrieved from the lake bottom. The water content of sedimen- ting seston (Figure 3) is removed between 500 and 200°C. Some of this water content may have been water of hydration, thus it was not removed until the temperature was above 100°C. Organic material was decomposed between 2000 and 600°C, and the more refractory calcium carbonate decomposed between 750° and 900°C. In comparison, water con- tent in sediment (Figure 4) is lower and is removed between 750 and 150°C. The area under each curve shows quantitative infermation on the materials of interest and differences are notable between the two samples. The organic content in the sediment is much less and is decomposed between 2000 and 550°C. The more refractory compounds in the sediment, primarily calcium carbonate, decomposes between 5500 and 1050°C. The DTA information when coupled with the chemical characteristics of the compounds of interest, provided the basis for the temperatures chosen for ignition techniques. In 1973, only one of the collecting tubes, comprising an upper and lower chamber, was used to determine the total dry weight of seston, organic matter, calcium carbonate, and ash. The seston vdthin the three remaining traps was used in additional Chemical analyses. The particulate organic carbon content of the seston was determined from 8 January 1973 to 8 January 1974. The material from 2. 6, and 10 meters was filtered onto precombusted glass fiber filters 14 Figure 3.—-Differential thermal analysis curve showing decanposition of seston from the 10 m sediment trap in Lawrence Lake. Decanposition took place in air and arrows indicate changes in recording resistance. 15 Figure 3 I T l l l l f T T l T I i F I” O 2 i a: Lu rence V E changes O x m 9 2 a: m I '— 0 g 70 I1 170 n. 470 II I. In ‘I 1 L4 l I l l l l l l 25 200 400 600 800 1000 Tempe rature °C 16 Figure 4.-—_Differential thermal analysis curve showing decanposition of sediment fran the lake bottom in Lawrence Lake. The decanposition took place in air and arrows indicate changes in recording resistance. IV'UI‘.’ CAUIF‘C" CNL)UIHCHMILJ 17 Figne4 ENDOTHERMIC : EXOTHERMIC 70.“. l l l l 1 g l l l l_ 1 25 200 400 600 800 1000 Temperature “C :ro cob T's“- '1'. J. .\ (,p. (F) (U ‘o I"! llav ‘00“ my a O D ’10 uni" et- “a ‘ sf.- . 5 ’f L! I 18 and processed by sulfuric acid-potassium dichromate oxidation (Strickland and Parsons, 1972). Each batch of acid dichrcmate was calibrated against a 3 mg 1'1 standard glucose solution and the results are expressed as glucose equivalents. The total nitrogen content of the seston was determined by Kj eldahl digestion (McKenzie and Wallace, 1954) followed by distillation (Markham, 1942). Before digestion, the sample was allowed to stand overnight with 4 ml of concentrated H2804 and 150 mg salicylic acid in a 30 ml Kjeldahl flask (Brinkhurst _e_t_ 2_1_1_. , 1972). Next day, 300 mg of NaZSZO3 was added to the Kjeldahl flask, then the flask was heated on a Kjeldahl apparatus for 5 minutes. Finally, 150 mg HgO red, 3 g K2804 and one Hengar granule was added to the Kjeldahl flask and digestion was continued on the Kjeldahl apparatus. The heat was increased very slowly to minimize foaming. Foaming usually ceased after 45 to 60 minutes, then the heat was increased gradually. After the sample cleared, heating was continued an additional 45 minutes. Three hours were generally required for canplete digestion. A 274 p g tryptOphan sample showed that 99.3% of the nitrogen was recovered by this method. The nitrogen standard used in all determinations was 0-4 m1 of a S g l'1 L-(-)-trypt0phan solution. Perchloric acid digestion (Strickland and Parsons, 1972) was used to determine the total phosphorus content of the sedimenting SeSton. Samples filtered onto glass fiber filters were placed into 100 ml volumetric flasks and the total solution volume in all cases was 50 ml. Slow digestion insured that all the phosphorus was released. Samples were held at the boiling temperature for 20 minutes, then allowed to boil vigorously until the total volume was about 2 ml and A)..."I ...Ibst 1C va- . AV" o 'Onv u -¢OvVn 22.x ...?!- I....c "89H "bvi 4 l 3' r h an Di ‘Is‘a.,' "5V. ‘ "1' uz‘tt LI. ‘7 I21 ) .14 19 droplets of perchloric acid refluxed down the sides of the flask. Centrifugation of the samples for 2 minutes at high speed was necessary to remove all the glass fiber particles before the color was developed. The surface area of calcium carbonate, precipitated from filtered Lawrence Lake water, was determined by a nitrogen adsorption method. The continuous flow method (Nelson and Eggertsen, 1958) was used with a Perkin-Elmer Shell Model 212 B Sorptometer. Untreated seston samples were used in x-ray diffraction analyses. Diffraction of x-rays by crystals can be used to identify crystalline materials, because the atoms of crystalline materials, such as calcite, are arranged in a regular manner and definite phase relationships exist between the scattered rays fran the atoms. X-rays incident upon a crystal mounted upon a rotating table allows the glancing x-ray angle to be varied, thus constructive interferences of scattered radiation will result. In these analyses, deflections of copper radiation were recorded with a seaming gonianeter that utilized a Geiger-Muller Counter tube. Sedimenting seston samples, collected during August 1973, were 5119.1 eCted to scanning electron microscopy. The photographs were used to evaluate the particle size, shape, and surface structure of the material collected on Nuclepore filters (Nuclepore Corp.). D. Physicochemical Characterization of Lake water Total alkalinity was determined as titratable base, according to Standard Methods (American Public Health Association, 1971). Lake water pH Was determined electrometrically with a Beckman Expandomatic 20 (Model 76-A) pH meter and temperature was measured _i_n 2131 by an electrical resistance thermister thermometer (Yellow Springs Corp. , Yellow Springs, Ohio). Oxygen values were determined by the Alsterberg modification of the Winkler titration (American Public Health Associa- tion, 1971), and silica was determined by the Rainwater and Thatcher method (1960). Total calcium was determined by flame atomic absorption (Jarrell Ash Model 82-700). To prevent calcium carbonate precipitation during storage, 0.3 m1 of concentrated nitric acid was added to each 125 ml lake water sample. Before calcium concentrations were determined, 5 ml of La203 solution (5% La3+ in 25% HCl v/v) was added to each 25 ml lake water sample to prevent anion and cation interferences. The ionized (free) calcium was estimated by a calcium ion electrode, Model 92-20 (Orion Research, Inc.) . TWO drOps of l M KNO3 were added to the calcium electrode standards and lake water samples to avoid any differences in total ionic strength. Calcium electrode standard solutions were mixed to reflect the ionic composition of the lake samp1es. Response of the calcium electrode to changes in calcium activity was rapid when placed in any of the standard solutions, although some drift did occur when the electrode was placed into the lake Samples. T o avoid any drift canplications, all readings were timed and the electrode was allowed to equilibrate for two minutes in a 10-3 M Ca2+ solution between each lake water sample reading. The Calcium electrode was stored in air between use and was placed into a -3 10 M Ca2+ standard solution for one hour before use. 21 E. Biological Data Chlorophyll a determinations on the lake water were conducted using spectrophotanetric techniques (Talling, 1971). O1! III. VARIATIONS IN SEDIMENTATION ANDNG THE SESTON COMPONENTS A. Introduction All collection of sedimenting seston was made at the central depression, Station A, thus extrapolation of this data to circumstances occurring within the littoral zone must be done with care. The number of depths sampled was restricted by the tensile strength of the tiller cable and physical strength required to retrieve the traps. Basic information on Lawrence Lake has shown practical locations within the epilimnion, metalimnion and hypolimnion occur at 2, 6 , and 10 meters respectively (Figure 5 and Figure 6). Resus- pension of sediments in dimictic lakes occurs during spring and fall Cirwlation (Davis, 1973), thus increased amounts during this period are impossible to avoid. Collection of resuspended material in the hYPOIimnion of Lawrence Lake during suimner and winter was avoided by suspending the lower trap at 10 m, about 2 m above the bottom. While depths chosen for this study conformed to physical limitations, they nevertheless allowed the collection of relevant information in the them\ally partitioned zones of the lake. Frequent collection reduced problems associated with living material growing on the sampler. In addition, the contents of the lower chamber were subtracted from the quantity of material in the “W3? chamber, allowing for correction for non-sedimenting material. The results are expressed as weight 111'2 day'l. 22 23 .uo>oo boa ucomoaoma oomwhom new we wanna mnemoo .Nemfl .oxmg mocoazmq ea <_cowumum um Moog oasumuodEou mo manoeu0mH--.m mesmHm ...l 24 OmQ >0 FOO Qmm OD 43m 23m ><§ mad. $.32 mmm 24... A HVD _ N— no. . a . m a L. .. L d i 10 H . .1 iv o. .. hulk-“Pm o m unaware 25 ..8>oo no“ “commence custom 05 we wanna ozomdo .32 60:3 85ng 5 < 533m um Gov 232033 mo mfiofiomH--.o ohnmfl 26 >07 HOnv omw muo— an ZDfi ><§ ma< m<§ mmm Z<fi Cw1Hid30 omtafim 27 B. Total Particulate Seston Seasonal variation in total seston for 1972-1974 is illustrated in Figures 7 and 8. It is important to note two breaks that exist in these data. During the spring of 1972, as the ice broke up, the buoy became trapped in the ice and the anchor was moved so that the 10 m trap touched bottom. Thus, data from 18 March to 31 March was anitted for this depth. In 1973, data for the period from.6IMarCh to 22 MerCh was lost after the tiller cable broke and all the traps were lost to the bottom of the lake. The traps were replaced on 23 MarCh, 1973. Lesser amounts of seston were collected during 1972 than during 1973 (Table l). The differences between spring circulation in 1972 and circulation in 1973 are important. A long cold spring in 1972 extended the period of circulation, whereas warm weather and less severe winds allowed the water to stratify rapidly in 1973. The dura- tion of circulation and stratification for the annual cycles 1972-1974 is given in Table 2. A comparison of Figures 5 and 6 suggest a circul- atory pattern of incomplete mixing after the ice broke up on 6 March 1973. Incomplete circulation during the Spring of 1973 is further illustrated by comparing dissolved oxygen (Figures 9 and 10), alkal- inity (Figures 11 and 12), hydrogen-ion (Figures 13 and 14), and calcium- ion concentrations (Figures 15 and 16) during the vernal period of each year. Temporary spring meromixis has been Observed previously in Lawrence Lake (wetzel et_al., 1972) and its occurrence is discussed in wetzel (1966b). The effect of temporary spring meromdxis on seasonal variation among the seston components will be discussed later. (- 41‘ I but. 28 F1 re 7.--Seasonal variation in total dry weight of seston 2 day' ) collected in sediment traps suspended at 2, 6, and 10 meter depths. Traps were located at Station A in Lawrence Lake from 8 January 1972 to 8 January 1973. Bars equal 1 S.E. Where no bars appear, the S.E. was less than the thickness of the line. (8 m" 29 Figure 7 I I I I I I I 1 I I r I 6’_ A we ice 2m 4- .. .>2h '1 In '0 E I I I I I I I I 6" -4 O c 3 6m mlr- _ 0 In E ...... 22'- - "' I I l I I I I I 36- - >. '0 10m 4- "" -~ 2- T L I I JAN'FE B'MAR APR'MAY'JUN'JUL'AUG'SEP'OCT'NOV DEC JAN 1972-1973 S.--Sensonal variations in total dry weight of seston collected in sediment traps suspended at 2, 6 and 10 Ira aps were located at Station A in Laarence Lake from Ht 8 January 1974. day‘1 total dry wt. m“? 9 31 Ice Ice 2ni e a I—ir — —+ I L l I I I I I I I I I I 6w) '--T=‘==P I I I II I I I IONT __F‘ p .. I I I I I I JAN FEB'MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN 1973-I974 32 emm o.nw mma mm.n EoH mmm «.mm mma ae.m so new N.mo cad mm.o EN mama mmm p.00 NON o.oa aod Hmfi 0.0m mad nv.m so flea n.~e maa nm.m EN mama flame hosesm mcflaom Hood“: canon new» coumom Hence .4-»mc N-E we mm cemmouoxo ma xpwuewso .oxmn oocopzmq ca quad - Nnma madame emuuoaaoo coumom Hmuou mo mum» nodumucOEHemm--.H mqm< Hmscg< m.mq o.¢m N.~m 00H oHH woa H.Hm H.H¢ o.wc :ufiamflsuuflu Hflwm H.mN o.v~ o.o~ w.- w.- N.mH m.om m.om fl.o~ coflumufimfiumuum.ugeasm v.0m m.m~ N.¢v m.mn H.qn ¢.vv n.qm ~.Nm m.mm cowumasuufiu mswuaw 5H.m NH.¢ mo.m Nw.~ ow.~ Nm.H Ho.m mo.m «m.o :ofiumuflwfiumhum papa“: mmsam>.ommuo>< mxflzum mo fine cu .mxmc mHV mm.“ H¢.h om.m om.H H~.H oo.~ ow.m ma.“ w.¢~ :afiumufimfipmuum pops“: ¢BQH nmxmc 0mg v.Hc m.¢v o.mm 05H “ma “ma m.om “.mq moa :oflumasoufiu Hamm fimch OONV N4: 0.8. HS 98 3m 93 m .3 0.3 W: 8388328 35% 50H 50 EN sea ac EN sod So am gm< momma “muumznoflqmmgo coumom Hmuoe AvoncflucouV--.N mqm32 mod. 14.2 mm“. _ _ .42., Omo >02 co ca mwsmflm 4O .Nama .oxmq mocohzmq :H < cofiumum pm Aa-a cosy xuflcfifimxam mo mauoHQOmH--.HH ousmfim 41 «no. Omo >02 POO omm OD< 43p ZDfi >2x<4 wruxx m<§ mmm Z<fi ‘N.Vt\_ _ m _ .v Weak <2 H. 3 we 3. \Jo a v. 3. . v u 3. o Ha museum (“0 HidBO 42 .22 .93 8:833 5 < 533m um ATH coca >353me mo 33303-22 PSwE 43 muo— omo >oz Foo mum 03< 43w 23w ><§ mm< m<§ mmd z02 owm .034. .5 m3). mm”. 24., 2 .5 _ 5 8 1 10— Q .0 3 1 d w. 8. 8 383 8 .o) w i .( 1v 1N _ v. O 2 83m... 46 .muma .913 85.53 5 4. 533m um mm mo $3303-23 0.2.3“. 47 muo— Uwo >02 #00 aww 03.4 ..Dp 23., >432 and. 14.2 mm“. r . _ _ . 0.. _ ..Q _ . .Q . a. . Q . C. .... \azs . 1 0d 1 .. 4m 0 3 .l f l d o... m... me o... m n J o ) . 4 - .w . «J o... . . N u . J I r , _ _ . xv”. _ 2‘. [o 3 22mm. 48 :H < :oflpmpm pm A -H wEV :oHpmpucoocoo + N .Nnma .oqu mucouzmq mu mo meu0.m0m.--.m. ousm.a 49 Omo \ 4 mm . ‘ now I -. c... >02 nu \ _ «ko— 50 $6 034 .2 22 >32 an? A _ u .. . . 8 8 8 no 2 a 4 mu 5 no 2 J no 8 oo oo oo 7 _ ./ _ a. «.32 mm”. 23. on .o. ... no 3 n3 .0 J . i. -m m. chem.» ('UJ) HidBCl mucopzmq :a < :ofiumpm um mH-H may newumhucmucou + N .mnmfl .oxmq mu mo mguoagomH--.oH unawam 51 muo— 80 >02 50 amm 034 42 22 >32 $2 532 mm: 2% ,, _ a _ d - q q 4 q q / N N— T ‘ /\8\ 8 I 3 8 3 . 6 o. T . 7 ) mu 8 — Fw)Hld30 2 0.53m 52 .33 8:333 5. €an banana m ow N2: >832, w SC 35038 noummm 5 :mm 38 £033 udfiwpo .323th £338 mo :oUfimomEou ammucmuuog m>3§mm--.§ PSmE 53 VA: muo— «no— 245 Omo _>OZ ...OO mmm :OD< 433 23.) >32. ma< 512 m mu Z<1_Omo >02 #00 mum 036. 431 231 >32 ma< «<2 mm... _ - NOlSBS :10 NOLLISOdWOO 39V1N3383d BAIlVTSH 5H ohsmflm .) LI U " ‘C R v ‘J '1 (H I ‘1‘ fl) 54 At 10 m the seston contained very small particles in an organic matrix (Figure 19a). This micrograph showed that the fine material formed a film over the surface of the filter. During drying, cracks formed and the material lifted up and away from the filter. Only 10 ml of the material was filtered onto the filter; nevertheless, in the upper mid-section of the micrograph it is possible to see that plugs of material pulled out of the pores in the filter. This evidence would cast some suSpicion on the use of filters to size fractionate particu- late materials eSpecially when larger volumes of water are filtered. Apparently the fine particulate material clogged the pores and reduced the amount and size of material that would otherwise pass through. The material in the seston at 10 m (Figure 19a) was mechanically broken down and well decomposed by the time it reached 10 m. Resistant diatom frustules were the only recognizable biological material present. Clumps of debris containing calcium carbonate crystals were present on the filter, however all material was covered with a gelatinous like coating. C. Organic Matter Analyses of the organic matter content in the seston showed the quantity of organic matter increased during spring and fall circulation (Figures 20 and 21). This indicated a considerable amount of organic material was resuspended during this period. Some alloChthonous organic material was introduced during autumn after vegetation was killed by frosts and carried from the littoral areas by fall rains (Wetzel and Otsuki, 1974). Flooding of these areas during the spring again transported more organic materials into the lake. 55 Figure 18.--Scanning electron micrOgraphs of seston caught in sediment traps during August 1973 and filtered onto 8 u Nuclepore filters. a: Material collected in sediment traps suspended in epilimnion, 2 meters (ZOOX). b: Material collected in sediment traps suspended in the metalimnion, 6 meters (ZOOX). 56 Figure 18 57 Figure 19.--Scanning electron micrographs of seston collected during August, 1973. a: Seston collected from 10 meters showing the fine particulate material and gelatinous organic matrix (SOOX). b: Enlargement of detritus showing crystals of calcite and fragments of diatom frustules in an organic matrix (SOOOX). 58 Figure 19 59 .Hmmmmm when on whoa: mafia may we mmoqxofigu ecu away mmoa was .m.m och .m.m w Hence mumm .mnma spanned m on whoa sumscmh w scum oqu oucopzwq cw <.cofiumpm um wopmuofi one: mouse .mnumow Hopes OH new .0 .N we mango :fl couuoaaoo Aa->me N-E mv copmom mo pcocomsoo oacmMHo ecu a“ mowcmgu Hmcommom--.om oasmflm 60 ”so. I «ma— Z<fi Own. >02 #00 mum 034 433 23? >52 «56. «<5. mm”. 264, Z-w WC 5 l_1(9p ON ousmfla 61 Figure 21.--Seasonal changes in the organic component of seston (g m’2 day" ) collected in traps at 2, 6, and 10 meter depths. Traps were located at Station A in Lawrence Lake from 8 January 1973 to 8 January 1974. 62 Figure 21 I I I I r I I I T I r I 1-5 ... 1714 2 m 1.0 - _ _ 0.5 - .- 3‘ W 3 .——.——1 , . ‘r—l— I I I I I I I I r I ‘7‘ E 1.5 _ - L 6 m g 1.0 .. _ to E 0.5 - _ .2 = m In 9 '===FJ——:l I I r’ I I I I I I 0 LS- - O: 10 m 1.0 '— ~14— "" 0.5 - - fl I l f I 7 7 7 l 7 I l 1 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN I973 - I974 63 During summer stratification in 1972 - 1973 the organic content of the seston was at times much lower than in 1973 - 1974 (e.g. June and July), however, the average amounts of organic matter during summer stratification were similar (Table 2). During 1972 organic matter content increased at 2 m during late July and August. This increase was also noted at 6 m during August and September. These observations agree with an increase in algal growth as evidenced by the amount of corrected chlorophyll 3 found at these levels (Figure 22). It is reasonable to suggest the settling rate of phytoplankton responsible for this increase in organic matter (Figure 20) took about two weeks, since the maximum level at 2 m occurred at the end of July and the first of August. The peak at 6 m occurred in mid- August through early September, indicating further growth took place at this level. At 10 m the maximum level of organic matter occurred in late August and early September then levels were reduced by mid- September. During 1973 a similar production of organic matter by phyto- plankton was observed during August (Figure 23). The maximum growth of phytoplankton took place at 6 m in the metalimnion and is represented by the seston caught in the 6 m trap (Figure 21) during early August. D. Calcium Carbonate 1. Solubility of Calcium Carbonate The apparent solubility of calcium carbonate in natural water is related to the partial pressure and solubility of carbon dioxide at any given temperature (Johnson, 1915; Johnston and Williamson, 1916). The 64 .Nnma .oxmq oucopzmg :H < coflomum pm Aq-a mag m.HH>:QOHOH;u wopoehpoo mo mcuoamomH--.Nm opsmflm 65 «no— Owo >OZ H00 omm OD< 43p ZDfi >32 mo< m<§ mm”. 244. 2: .wa \ M. _\ _ .9 .Q _ J Wm _ a a ON .0 N— J 1 1 ('w) HidBCl NN onsmua 66 m 67 mxo— IN— UmQ >02 POO Qmm OD< 43.. 23., >32 an? $32 mum ZS) — \ _ A J _ C r >_ N m v . 3 0 mm _m.o ('LU) HldBG mN enema 68 formation of HZCO3 and its subsequent dissociation into Hf and HCO3- ions determine to a large degree the solubility of calcium carbonate. A practical definition of calcium carbonate solubility is based upon the dissolution of calcite suspended in pure water (Hutchinson, 1957). In an Open system, calcite will dissolve until an equilibrium is established, based upon the interdependence of these solute species: coz, HZCOS', cosz’, H+, ”COS”, and on". At this point, further dissolution of calcium carbonate does not occur unless the partial pressures of CO2 increases. The solubility of calcium carbonate under different carbon dioxide pressures and temperatures in pure water are based upon the work of Frear and Johnston (1929) and are given in Hutchinson (1957). All calculations in this work are based upon these values. Berner (1965) used two equations to describe precipitation of calcium carbonate in sea—water and these equations are used to describe calcium carbonate precipitation in Lawrence Lake. When an increase in pH occurs the following equation describes subsequent changes among the involved ionic species: Ca2+ + ZHCO ‘ : Caco3 + (:02 + H20 (1) 3 Whenever the pH decreases the following changes occur: Caz+ + cosz‘ : Caco3 (2) pH changes in lake water are related to the concentration of H+ ion and this parameter is ultimately related to the partial pressure of C02 and chemical enhancement of C02 diffusivity (WOod, 1974). The H2C03 in turn determines the proportion of HCO ', CO32', and OH- present. 69 Figures 13 and 14 show i50pleths of pH change in the water column during 1972 and 1973, respectively. These changes indicated that an increase in pH does occur through the summer in the epilimnion and metalimnion; although, the pH does not rise above 8.4. The change in pH means calcium carbonate precipitation would proceed in accordance with equation (1). The initiation of calcium carbonate precipitation in the hypolimnion would take place by equation (2); since, there is a decrease of pH in the hypolimnion. Changes in alkalinity during 1972 and 1973 (Figures 11 and 12) indicate the values decreased in the epilimnion and metalimnion during summer stratification. A correSponding change in the isopleths of Ca2+ concentration is observed during the above mentioned period (Figures 15 and 16). The Ca2+ concentration was progressively reduced in the trophogenic zone, while an increase occurred in the hypolimnion. These data all indicate a considerable precipitation of calcium carbonate was taking place. 2. X-ray Diffraction Analysis of Seston Preliminary samples of seston were collected at 10 m.in Lawrence Lake during 1970 to determine what crystalline polymorph was present. X-ray diffraction investigation of this material revealed calcite was the only crystalline material present in the sample. It is supposed this crystalline form precipitates out of Lawrence Lake; although, it is plausible the calcium carbonate may form an amorphous matrix with the organic material as well (Figure 19a). 70 3. Calcium Carbonate Content in Seston Calcium carbonate content in the sedimenting seston had vernal and autumnal maxima in 1972 (Figure 24). In 1973 (Figure 25) an autumnal maximum is obvious; however, the vernal maximum is less pro- nounced. These maxima correspond to periods of circulation and are caused by resuspension of material from the bottom sediments. The short period of circulation (cf. page 36) during the spring of 1973 raised less material from the bottom sediments. Autumnal circulation in 1973 (Figure 25) resuSpended perceptibly more calcium carbonate presumably because of two factors: (1) fall winds were stronger; and (2) more calcium carbonate was precipitated during the preceeding summer season. One of the unmistakable differences between the two annual patterns (Figures 24 and 25) is the larger quantity of calcium carbonate that precipitated out during summer stratification in 1973. Approximately 5 times more calcium carbonate precipitated in 1973 than in 1972 (Table 2). A shorter circulation period.and elevated concentrations of Ca2+ (cf. Figures 15 and 16) during the spring of 1973 were directly related to this dissimilarity. The lowered amount of calcium carbonate precipitation during ice cover was anticipated, insofar as lower temperatures increased the solubility of C02 and reduced metabolic activity to very low levels. 4. Cause of CaCO3 Precipitation The precipitation of calcium carbonate can be divided into three broad categories: (1) abiogenic precipitation; (2) precipitation by freshwater bacteria and plants; and (3) precipitation by animals (Pia, 1933). 71 FiguEe 24.--Seasonal changes in calcium carbonate content of seston (g m“ day-1) collected at Station A in Lawrence Lake. Traps were located at 2, 6, and 10 meter depths from 8 January 1972 to 8 January 1973. Bars equal i S.E. Where no bars appear the S.E. was less than the thickness of the line. 72 Figure 24 3,- I I I I I I I T r f I I — ice Ice 2In 2- _ y F.- ..1 I I I _. 7), 6m 3 .. 2” F. ‘ 'E d? .4. -41 “W 931- PH ‘ L) ° ._._ ”l 3_I I I I d IOIn 2' —h + .. '4- I- - r—‘_l r—I I I I I I I ‘ JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN I972-I973 73 Figure 25,--Seasonal changes in calcium carbonate content of seston (g m‘2 day'l) collected at Station A in Lawrence Lake. Traps were located at 2, 6, and 10 meter depths from 8 January 1973 to 8 January 1974. 74 Figure 25 3| fir T I I I I 1 I I I I T q '°° 7 Ice r- 2". -I 2 - ”‘7 1 - -I I t ‘ h L 1 I I I I I I T I I 3 h ‘ ‘1 I 6rn __ q a 00003 In" day" ——1 I I I T ’I’ I I I I I —-I b— —I 3" I0m - ‘ h d —I 2- - 4 .4 I- ‘ JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN I973 - I974 7S Abiogenic precipitation of calcium carbonate in Lawrence Lake may be caused by changes in temperature and loss of carbon dioxide to the atmOSphere. Otsuki and Wetzel (1974) found the groundwater and inlet water from two small streams flowing into Lawrence Lake contained elevated concentrations of calcium (ca. 90 mg 1'1) and total alkalinity (ca. 5.5 meq 1‘1) as compared to average values of calcium concentra- tion and total alkalinity at Station.A (68 mg l'1 and 4.4 meq 1'1, respectively). Since the inlet water and lake water were already saturated, it is possible some free or equilibrium CO2 was lost to maintain equilibrium values. This reaction should proceed according to equation (1) with an attendant precipitation of calcium carbonate and release of free CO2 to establish equilibrium conditions. However, photosynthetic activity of submersed macrophytes in the littoral zone and their attached microflora would induce calcium carbonate precipita- tion (Wetzel, 1960, 1970; Rich et 31., 1971; wetzel gt al., 1972) and tend to overshadow this abiogenic process. Mbreover, the surface waters of Lawrence Lake are supersaturated with respect to calcium carbonate, so the dissolved C02 is not in equilibrium with the atmosphere and this would indicate loss of CO2 to the atmosphere does not play a primary role in calcium carbonate precipitation in this study, especially in the Open water. Temperature change has been implicated as the causal factor in the initiation of CaCO3 precipitation (Brunskill, 1969) and a time lag 0f one month was observed between the onset of calcium carbonate precipitation and a decrease in total CO Otsuki and wetzel (1974) 2. indicated temperature was not the direct causal factor in.the initia- tionof calcium carbonate precipitation based upon outlet water and 76 surface lake water of Lawrence Lake. In this work, a careful examina- tion of temperature (Figures 5 and 6), alkalinity (Figures 11 and 12), Ca2+ concentration (Figures 15 and 16), and calcium carbonate content in the seston (Figures 24 and 25) indicated that all these parameters were closely interrelated in calcium carbonate precipitation. Increases in temperature and light intensity, coupled with an abundant nutrient supply, promote rapid algal growth in spring (Figures 22 and 23). Likewise, considerable calcium carbonate is precipitated during this period (Figures 24 and 25). This information indicated calcium carbonate precipitation results from both increasing temperature and photosynthetic activity. A comparison of Figure 6, Figure 23, and Figure 25 at the 6 m depth over the period June, July, and August clearly show increases in temperature, chlorOphyll a, and calcium carbonate content in seston are closely correlated. While it is unclear what factor or factors initiated calcium carbonate precipitation, it is clear that photosynthesis facilitated calcium carbonate precipitation when free CO2 and/or bicarbonate ions were utilized. Phosphate combines with the seston to form colloidal phosphorus (Lean, 1973). Some of the colloidal phosphorus may be hydrolyzed directly to phosphate; however, some of the colloidal phosphorus becomes biologically unavailable and is precipitated out of the trophogenic zone. The reduced collection of phOSphorus at the 6 m depth during June and July indicated phosphorus was tied up in growing organisms (Figure 26). Later, during August and September, considerable quantities of phosphorus were collected, presumably as dead algal and 200plankton remains. During this same period of intense algal growth in 77 .32 33:3 w 8 22 began as 50$ mfiame some 2 Ea .e .N pm 6333 363 womb. .33 3533 5 < 533m 3 @3qu8 833 we $-33 NYE m5 33:8 30333 H33 5.. 533.23 38331.3 333m 78 Vno—Imko— 24:, 0mm. >02 ...00 amm OD< 43w 23.. ><§ mad. m<§ mm“. 24.. 3-“) d 5 w l_/(ep ON mhsmflm 79 June, July, and August (Figure 23), large quantities of calcium carbon- ate were precipitated (Figure 25). This observation supports the contention photosynthesis does play an important role in decalcifi- cation of water in the trophogenic zone. The assimilation of free CO2 and/or bicarbonate ions by aquatic plants and resulting calcium carbonate precipitation has been observed and well studied in natural waters (Ruttner, 1921, cited by Ruttner, 1963; Gessner, 1959; Schelske and Callender, 1970). Bacteria play a minor role in inducing calcium carbonate precipitation; however, they are involved in forming larger crystals in the sediment (Kusnezow, 1966). It is unlikely that bacterially induced precipitation is an important process in Lawrence Lake, since, large (e.g. 8 cm diam.) calcium carbonate crystals are not found. Likewise organisms such as fresh water clams and snails are not considered important here; because, they do not initiate calcium carbonate precipitation in the pelagic zone. 5. Supersaturation with Calcium Carbonate The apparent supersaturation with calcium carbonate in Lawrence Lake was investigated during 1973. As described in the methods section, total calcium was detenmined by flame atomic absorption and the ionized (free) calcium was determined by a calcium ion electrode. Total calcium and ionized calcium determinations were sumed and averaged over these depths: O, 1, 2; 3, 4, S, 6; and 7, 10 meters. The mass in mg of suspended or colloidal Ca2+ 1’1 during 1972 - 1973 was obtained by subtracting the ionized calcium determinations from the total calcium values (Figure 27). 80 .2326 ~39: 3 98 .o .N how :93 mg 5338 popcomgm mo 33550 .< 533m um 9:3 85.964 5 popcommsm 3A +~mu may E333 33038 5 3033.8?22 833m 81 0mm. >02 ._.00 mum OD< 43a. 23.. >42 ma< «<2 mm“. Z<fi Qua d 11 1 d d ‘1 d d d 01 l s;u— cao .0. L c 0 IO {00 cv Dun I.zO|P.H I 5N ou:Maa 82 During the annual cycle of colloidal calcium carbonate there was an average of 37 mg Ca2+ l'1 suspended in the lake water. There was no period when the lake was undersaturated. The level of colloidal calcium was less during spring circulation (6 March - 26 April). The lower spring values were related to an increase in ionized calcium which indicated calcium carbonate was redissolving. A rapid increase in colloidal calcium content occurred after stratification until June, July, and August when the levels dropped. The drop in colloidal calcium during this period is related to elevated levels of algal growth in the metalimnion (Figure 23) and precipitation of calcium carbonate (Figure 25). 6. SEM Photos of Calcite Crystals Water samples collected at 6 m during May 1973 were filtered onto a 0.4 u Nuclepore filter after the water was first filtered through a series of larger Nuclepore filters. The size of these crystals (Figure 28a) are larger than ordinarily occur in the water; since, vacuum filtering can remove C02 from the water (Felfoldy and Kalke, 1957) and cause crystal nucleation and growth to occur. The crystals range from 1 u to 6 u in length and show a dendritic growth pattern. Dendritic development occurs when solvent molecules are unable to rapidly diffuse away from the crystal surface where growth is occuring; thus corners located in less severely blocked areas continue to grow at a more rapid rate (walton, 1967). Impurities are also suggested as playing an important role in causing dendritic growth. Dendritic crystals provide a surface prone to entrap surface adsorbed compounds and this mechanism.may be important in coprecipitation. 83 588$ cascades 2: 5 its: 3580 cm :H pomponEo mamumxho oufioamo cuflz.w::oummhom may a“ mwuouomn mqazonm maouoe oa scum empooaaoo coumom an .AxQooNU mama km: .mhouoe e um wouuoafioo gown: seam houaflm chomoaosz : «.0 m ouco vohouafim mamumxho ouwuamu ”m .oxmq oucopzma scam pouooafioo Hmflpoume mo mammquHUHE couuoofio mcficqmom--.mm oHSMwm Figure 28 84 85 E. Ash The most obvious characteristic in the annual pattern of ash content in the seston during 1972 (Figure 29) and 1973 (Figure 30) was an increase during spring and fall circulation.when resuspension of the bottom sediment occurred. Ash content in seston was higher during the months of May, June, and July then tapered off during late summer (Figures 29 and 30). This sedimentation pattern suggested diatoms were primarily involved and agrees with data from.Manny (1971) and unpublished algal data (Wetzel, personal communication) on Lawrence Lake. Their data showed larger diatom populations during late spring and early sumner, as well as late fall and winter. Annual patterns of SiO2 content (Figures 31 and 32) in lake water also showed a.more rapid utilization of silica during.May, June, and July than other periods of the year. Examination of seston by light microscope and scanning electron microscopy showed large numbers of diatom.frustules were present on the filters (Figures 183, 18b; and 193, 19b) during most of the season. Ash content in seston may have been increased some- what by clay particles, but most Observations supported the contention that diatom frustules were the major component. 86 .mama asascmn w ou mama suaqeau m Eoum mcumop .835 S com .o .N pm @383 who: mam; .33 85.33 5 < 5395 um popuofioo coumom mo :KAmw NEE 3 “Emacs :3 fi :oflmflmc, anaemmom--.mm ohsmfim 87 nuoplnng Z43 Own >02 ...00 mum OD< 43.. 233 ><2 1&4 ”.32 mm“.— 24:. n6 0.— n.— "2 o O. In ._' “2 o 0. IO ...? 6 l-/(ep a-tu use mN opsmfim 88 Figure 30.-—Seasona1 variation in ash content (g m’2 day'l) of seston collected at Station A in Lawrence Lake. Traps were located at 2, 6, and 10 meter depths from 8 January 1973 to 8 January 1974. 89 Figure 30 m'2 day" aslI ."‘ 0| 0 d (D .1 q -I .. .4 O (D l 2In LO'- ' o 005'— _ '- r——1—-1 D ‘FL r14— I ”T I r I I I I I I ‘1 L5- _ brn LO- - 0.5L m m - I 71 I I I I I I I L5 L0 (l5 lOrn Pl 1W WITH l I I I I I I l I T I JAN FEB MAR APR MAY JUN JUL AUG'SEP'OCT Nov DEC JAN 1973—I974 90 .22 .93 BEES 5. < 838m Am r; 95 Now mo 93283-23 «Ema muo— Omo >OZ FOO amm 03.4 .5“. 22, >32 ma< $.32 mmm 23, 91 ._ t A (.../x A /~_\ _ t a. m- o_ 034 a. o. : o o. : . \o o. m m 2 o. 1 o c k c- . v o o— 9 4 WV .. a . _ p Flo S. 2ng /é w ('UU) HldBCl 92 .22 .93 86qu 5 < 833m 3 r; 95 New mo 93283-23 8sz 93 muo— Omo >OZ ._.OO Qmm 03.4 .5... 23., >32 «54 $12 mm”. 23, .— _ d d _ ~ a I s A t\2& fig Km. _ «Mn N. 9 C— 2 m”\\—— : 1 N_\/\lo_ .o. T Z a I I 1m m . We m . m r a o. o. .o H I A g 7 w r a o. i. o. . - no N I —© ¥ I p r _ _ p . _ _ p 00 3 Emma IV. SEDIMH‘ITATION OF METABOLICALLY IMPORTANT PARTICULATE MATERIAL FROM THE TROPHOGENIC ZONE A. Particulate Organic Carbon The annual cycle of particulate organic carbon (POC) content of seston revealed precipitation of POC was relatively low throughout summer stratification and.was further reduced under ice cover (Figure 33; Table 3). The correspondence between chlorophyll a_distribution in the lake (Figure 23) and POC content of the seston (Figure 33) during 1973 implies dead and/or living algae were a major component of the organic seston. Increased algal growth in the metalimnion is clearly reflected in POC sedimentation at 6 and 10 meters during July and August. Spring circulation POC values were 2.7 times higher than fall circulation values (Table 3). Higher spring POC values suggest the resuspended organic material contained more oxidizable carbon than seston collected during fall circulation. A comparison of the annual cycle of POC (Figure 33) and the organic matter cycle (Figure 21) shows the heterogeneity of the organic material in the seston. General similarities are noted between the two carbon determinations, but the organic matter values are considerably higher throughout the season. The disparity between these two values are related in part to the dissimilar methods used. Organic matter content was determined by loss of weight upon ignition at 550°C for one hour; whereas, POC was determined by acidedichromate oxidation based upon glucose carbon equivalents. The ignition method would include 94 95 .vnmfi thscmw m cu muma thoth w scam mzumow Hopme ca pan .0 .m um wmumuoH who: mgmnw .oxmq monopzmq a“ <_:ofluwum um wouumaaou ocummm mo A -xme N -E woo mv :onumu oficmmpo oumfisufluhmn ca cofiumflhm> Hmcommmm--.mm madman 96 Vko—I nua— Z<fi_0mo_>02_._.00 n. w w OD<_._ D 3_ZDU_><§_mn_<_m<2_ mm “#21:; - E — — _ I; T ... Eo— 1 i _ P p _ p _ LI 1 l T .l. T I. p _ _ _ _ L _ E , FFEIF 1 .. rl I. E« I L mo. 1 «.0 V.0 0.0 0.0 «.0 v.0 0.0 0.0 «.0 V.0 0.0 0.0 Z-w 00d lJep mm 8&2 97 ammo. oomo. mmmo. om.m Hm.“ oH.n n.oa m.HH H.HH ammum>< Hmacq< flawsum we use op .mmme mam oaao. «ado. omno. mo.H mm.H Hem. mm.o em.m mm.m :oHumommHumuum yous“: whoa Anzac 0mm mna. mmH. mom. o.o~ o.oa m.mH m~.m v.oa em.m cofiumasuufiu Ham» ammme comm memo. momo. memo. mo.m vm.m mm.m e.NH w.eH N.mH coaumoflMMHmupm possum flmmme GNU Boa. Bea. oea. m.mH o.HH mn.m v.m~ m.o~ m.om cowumasuuwu mcfiham Ammme 5mm nnmoo. «ammo. mcfio. mmm. mew. omm. n«.H mm.H mo.m :ofiumofimflumhpm umucaz whoa Ema Em EN Ema so EN Ema Em EN maponmmogm :mmouuflz 00m .H-»m0 E m 3 mm pommmhoxm mm mahogmmonm . -xmp N-E we mm pommohmxo ohm ammonuflc paw conpmo oficmmuo mamazuwuumm .vamu-mamfl mefipse exam «unease; mo : ummm on“ :H mahonamogn Hmuou one ecomouuw: Hampaonx .muomv conhmu vasomuo opmasuHuuwm mo moumu cowpmucoEHpom--.m m4m02 ...00 mum 03.4 437 233 ><§ mo< K32 mm“. 247 It42F>IaI>+ 6 l_/(ep a-tu N am otsmum 101 Kjeldahl nitrogen content of seston was shmilar at all depths measured. The slight differences in quantity were related to the time required for the material to reach the hypolimnion. During August the elevated quantity of Kjeldahl nitrogen found at 2 and 6 meters appeared two weeks later in the 10 meter trap. C. Total Phosphorus Annual changes in total dissolved phosphorus have been measured in Lawrence Lake (e.g. Wetzel, 1972, Figure 1 and 2), and variation between depths has not been great. The pool of dissolved total phosphorus appears to be relatively constant. A.uniform level of total dissolved phosphorus yields no information on turnover rates and availability of phosphorus in the trophogenic zone. Phosphorus content in the seston; however, does give indirect evidence of availability and factors that may regulate availability. Considerable amounts of phosphorus were resuspended during spring circulation (Figure 26 and Table 3). Levels of total dissolved phosphorus were not appreciably increased during spring circulation (wetzel, 1972). The resuspended phosphorus was either not soluble or rapidly taken up and stored by phytoplankton. Large quantities of resuspended CaCO3 during spring circulation (Figure 25) may have reduced the total dissolved phosphorus. MUch of the resuspended phosphorus may have adsorbed to colloidal and particulate calcium carbonate (Ohle, 1935, 1937; Gessner, 1939). Otsuki and wetzel (1972) have shown that more than 74% of phosphate ion was found to precipitate with calcium carbonate as the pH was raised to 9.5 - 10. 102 The rate of phosphorus removal at 2 m remained high until early July (Figure 26). The elevated rate of phosphorus precipitation during this period was correlated directly to the annual pattern of chlorophyll a_(Figure 22), which showed phytOplankton activity was also high until early July. After July, the rate of phosphorus precipitation at 2 m remained low until fall circulation occurred in late October. Rates of phosphorus removal at 6 m were very erratic until July. The fluctuation between high and subsequently reduced levels reflect periods of rapid phytoplankton growth, followed by periods of phytoplankton death. In August much of the epilimnetic phosphorus was displaced into the metalimnion where it perhaps contributed to the stimulated phytoplankton growth at 6 m (Figure 23). After August, successively lower levels of phosphorus were collected at 6 meters until fall circulation occurred. The quantity of total phosphorus retained in the 10 m.traps was higher whenever substantial phytoplankton reduction occurred in the trophogenic zone. The 10 m seston also reflected lower amounts of total phosphorus when rapid growth and storage of phosphorus occurred (cf. Figures 23 and 26). The rate of phosphorus removal was much reduced during winter, because phytoplankton growth is very low under ice and snow cover. ‘V. ASSOCIATION OF IRON AND VITAMIN B12 ‘WITH CALCIUM CARBONATE A. Iron Experiments 1. Introduction Additions of iron to Lawrence Lake water are immediately precipitated by inorganic compounds and are ineffective in stimulating algal C14 uptake (wetzel, 1972). wetzel (1972) found chelator compounds such as nitrotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EUI‘A) consistently stimulated algal growth when added in the proper ratios. The photosynthetic rate doubled within 4 hours. Additions of NTA were in the ratio of approximately 100 ug liter.l iron : 100 pg liter.l NTA; however, greater concentrations of EDIA were required (500 ug liter'l). Natural amino compounds also complexed iron and stimulated phytOplankton growth. Experiments on iron availability by Schelske (1962) have shown similar results. It is unlikely that trivalent iron is analytically detectable in alkaline lakes (Hutchison, 1957). Iron is retained in lake water as colloidal ferric hydroxide, adsorbed onto particulate matter, and in canplexes with natural chelator compounds. Dissolved organic matter has been considered to function as a chelator of metals in lakes (Saunders, 1957). 103 104 Laboratory experiments demonstrated the complex nature of iron removal during calcium carbonate precipitation. 2. General Procedures Water was collected from 6 meters in Lawrence Lake on 18 April 1973, filtered (984 H Reeve Angel), and stored at 15°C for three weeks before use. Triplicate samples of lake water were removed and allowed to equilibrate for 2 hours at 25°C before each experiment was started. Initial iron, calcium, and pH determinations were made, finally iron was added to give 1000 ug literd. The sample flasks were placed on magnetic stirrers for one half hour after which subsamples were removed, filtered, and examined for iron and calcium content in solution and on the filters. Calcium precipitation was induced by adding 0.2 M NaOH to each flask whereby the pH was raised by increments of 0.5 each time NaOH was added. Samples were stirred one-half hour after each addition of NaOH. Subsequently, subsamples were removed to determine iron and calcium content on filters and in solution. This procedure was repeated until the pH reached 9.5. The experiments were first done without any additions of chelator compounds, then repeated with EDTA and yellow organic acid extracted from Scirpus subterminalis Torr. (Otsuki and Wetzel, 1973). Changes in calcium concentration were monitored by flame atanic absorption (Jarrell Ash Model 82-700). pH was determined electrometrically with a Beckman Expandomatic (Model 76-A) pH meter. Total iron concentrations were determined colorimetrically (Golterman, 1969). Iron samples were digested 15 minutes in a hot 10% NHZOH°HC1 and 4 N HCl solution, after which bathophenanthroline was added to 105 develop a red-colored iron complex. The complex was subsequently extracted into hexanol and assayed spectrOphotometrically (Lee and Stumm, 1960) . 3. Results Experiments on iron and calcium carbonate interactions demonstrated iron was substantially removed when the pH was increased ‘ to 9.0 (Table 4). More iron was contained in Lawrence Lake water at W pH 9.5 than one would expect if pure solution chemistry was involved. This increase in iron content under these conditions may have been related to two conditions; equilibrium had not been reached and a j ‘ longer lapse of time before sampling would have lowered this value, or ’ naturally occurring organic compounds in Lawrence Lake water may have chelated some of the iron. When either EDTA or yellow organic acid was added, some iron remained in the solution after the pH had been increased to 9.5. Apparently, the chelator compounds were able to canplex metabolically significant amounts of iron and keep it in solution. Addition of EDTA and yellow organic acid reduced the rate of CaC03 precipitation (Table 4). When no chelator compound was added, 21% of the CaCO3 precipitated at pH 9.0, and 50% at pH 9.5. When EUIA was added only 3.7% of the CaCOS precipitated when the pH was increased to 9.0 and 54% at pH 9.5. Additions of yellow organic acid lowered the rate of CaCOS precipitation at 9.0 to 2.2% of the total amount in solu- tions and to 57% at pH 9.5. These data suggest CaC03 formed a canplex with the chelator compounds at pH 9.0 and when precipitation did occur (pH 9.5) the chelate was removed. Calcium was able to canpete with iron for chelating ligands. Such a mechanism would prevent, or at least 106 H.0m ¢.mm m.mm H.mu o.am m.um m.au a.NN N.em c.mm am.u Hm.~ m.m om.u a.ae oaau m.am om.~ m.mo Gama 0.4H e.mu a.mm mam compo o.a --- a.ue --- came --- a.me --- oeou --- V.Ha --- Ns.m m.m --- m.~o --- oama --- m.mo --- oauu --- m.ua --- mNm flom.mm fimum H.0H4u :_Hom a pad : Me a u a c o a uaa e do u u a c H.0Hau :“Hom mo H-H Em AM-H mam H-H em Au-u mam MH-H wee ”4-H am +Nmu e Hooch +~m0 em Hence +Nmu em Hooch mq-H ms am.mm mu-u m: ooum eesoascu poumaoeu oz 0Hu mo mmoq--.m mqm6u mm was um unauumaemum 06: mm a .maoaammu .emmmsosmm am .Hmeammm .Naamomma 4N mm .uom .mommmam .seemmmoa m .Nuaosmo .oamamoek m mm .eum 4m.m .eamoummm .mNamsaHos m mu. .momomau .moeNmNa m mm .uue --- --- .mammmeeoa mm --- --- .eHmNmmaaH mm mm sauce a m: mm ”a a m: mm ”a 898 66m: :.Hom Nam we as N mam: :.Hom Nam mo as a .Num :mEmum> mo meofiumhucoueoo can now mmz.:m sepmm hope: oxwa ca acoueou 0>Hm mm sump one .om.m :n.ou mm.m mo scum xawflomu common m gHMKr 8 “#3 HO 0HQNH OUAHNMHGNr W0 WHW~AHMAH<11.N. EQH. 115 u a mug -!I: .(mnlr H6>us ma 6:0 um unmoumacmmm mu m .memmes .Nmemauuu 4N .Hommos .Nmovmam 4N mm .uon .mmosmm .soamama m .ouNmm .mNNmoa m mm .amm mm.m .oummesm .NmaeomaN m a¢.m~ .aouaemm .Nfimasae m mm .uue --- --- .meammmes mm --- --- .Naoamma mm mm sauce a m: mm ..a a 9 mm "a 836m emms :.Hom Nam mo as N emu: e.Hom Nam mo as H .Nsm afiemum> mo mHe>eH :ofipmupcmoeoo 03» now n0>wm mm «one one .om.m mm 60 om.m mo scum savages momma» mm3.:n 0:» “came whouawm :o penance Nam :flsmuw>.:o name we canny ouqmfihm> mo mflmxame<--.m mqm02_._.00_n_ mm .OD<_.._D D_ZDD_><§_mn_<_m O 2 1.. U 0 Q “J (I) U D Q’ 6“ 00.. \ .1 D ‘1 2 D D >. '1' E \ ~ ‘ III 7‘ I I l \ \ ’1 1 A Cr 0. <1: Q <1 2 0 LL! U. Z < 7 9'0”"- M '------------------------ -- ‘ s ‘ $0.. 129 was generally higher than the 2 and 6 m values and also displayed more fluctuation. The higher 10 m carbonznitrogen values were pr0bab1y related to rapid nitrogen release by bacterial degradation. The carbonzphosphorus ratios of the seston showed very rapid changes and considerable variation throughout the year (Figure 37). The 2 m values were high under the ice because the phosphorus content of seston was low. Just before spring circulation the ratio dropped rapidly, indicating an increase in the phosphorus content of the seston. This increase was related to diatom growth under the ice (wetzel, unpublished data). The ratio remained low until late July, then it increased sharply. This sharp increase marked the rapid displacement of phosphorus into the metalimnion. The carbonzphosphorus ratio remained somewhat elevated until fall circulation occurred in late October. The 6 m carbonzphosphorus ratio was lower under the ice than either the 2 m or 10 m value. Phosphorus was being precipitated and 110t utilized. The ratio increased rapidly at 6 m in mid-July; however, .it declined as phosphorus was displaced from 2 m into the metalimnion. (Zonsiderable phytoplankton growth took place in the metalimnion during this time (Figure 23). By late October the ratio increased once again lxntil fall circulation rapidly lowered the ratio. At 10 m changes in the carbonzphosphorus ratio were less (trematic; however, they reflected changes that were taking place in the trophogenic zone. 130 Figure 37. —-Seasonal changes in carbon: phosphorus ratio by weight (x 105 ) of seston collected at Station A in Lawrence Lake. were located at 2, 6, and 10 meter depths from 8 January 1973 to 8 January 1974. Particulate organic carbon is expressed as mg m“2 day'l ; whereas, phosphorus is expressed as mg m‘2 day’l Traps 131 Figure 37 ice 14 ice' _ 2 I Set: _ m 2m m 0 _ £0.02, .3 0:3 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN 1973 -1974 VII. SUMMARY.AND CONCLUSIONS Sedimenting seston was collected into improved sediment traps during a two year period and analyzed for total dry weight, organic material, calcium carbonate, and ash content in Lawrence Lake. During the second year particulate organic carbon, Kjeldahl nitrogen, and total phosphorus content of seston were examined to illustrate when metabolically important compounds are removed from the trophogenic zone. Conclusions reached were: 1. Sedimentation rates of organic material and ash were similar during the two year period; however, the rate of CaCOs precipitation was 5 times greater in 1973 than 1972. 2. Colloidal calcium was present during the entire year in Lawrence Lake and the average quantity of suspended CaCOS was 36.7 mg 1'1. 3. Scanning electron micrographs of seston collected at 10 meters showed that an organic matrix covered all material and the organic material clogged pores in the filters. 4. Sedimentation of total phosphorus showed a marked displace- ment into the metalimmion and hypolirmion when severe decalcification occurred in the epilimnion. 5. Material is resuspended from the bottom of Lawrence Lake and the quantity resuspended varies with the strength and duration of vernal and autumnal winds . 132 133 6. Sedimentation rates of nitrogen and particulate organic carbon were comparatively constant throughout the season and were closely related to phytoplankton activity in the trophogenic zone. 7. Laboratory experiments on interactions between CaCOS and iron suggested no direct adsorption of iron onto CaCOS particles; however, CaCO3 and iron precipitation rates were influenced by the presence of organic compounds. 8. Investigations on vitamin B12 and precipitating CaCO3 relationships suggested vitamin B12 was removed in association with precipitating CaCOS. LIST OF REFERENCES LIST OF REFERENCES American Public Health Assocation, American Water Works Association, and Water Pollution Control Federation. 1971. Standard methods for the examination of water and wastewater including bottom sediments and sludges. 13th ed. American Public Health Association, New York. 769 pp. F3 Berner, R. A. 1965. Activity coefficients of bicarbonate, carbonate on and calcium ions in sea water. Geochim. Cosmochim. Acta 29:947-965. Brinkhurst, R. 0., K. E. Chua and N. K. Kaushik. 1972. Interspecific interactions and selective feeding by tubificid oligochaetes. Limnol. Oceanogr. 17:122-133. Brunauer, S., P. H. Emmett and B. Teller. 1938. Adsorption of gases in multimolecular layers. J. Am. Chem. Soc. 60:309-319. Bruiskill, G. J. 1969. Fayetteville Green Lake, New York. II. Precipitation and sedimentation of calcite in a meromictic lake with laminated sediments. Limnol. Oceanogr. 14:830-847. Bundy, L. G. and J. M. Bremner. 1972. A simple titrimetric method for determination of inorganic carbon in soils. Soil Science Society of America Proceedings 36:273-275. Chau, Y. K. 1973. Complexing capacity of natural water - its significance and measurement. J. Chromatographic Sci. 11:579. Chave, K. E. 1970. Carbonate-organic interactions in sea water. Pages 373-385, In: D. W. Hood, Ed. Organic Matter in Natural Waters—University of Alaska. 625 pp. Chave, K. E. and E. Suess. 1970. Calcium carbonate saturation in sea water: Effects of dissolved organic matter. Limnol. Oceanogr. 15:633-637. Conger, P. S. 1942. Accumulation of diatonaceous deposits. Jour. of Sed. Petrology 12:55-66. Davis, M. B. 1973. Redeposition of pollen grains in lake sediment. Limnol. Oceanogr. 18:44-52. 134 135 Droop, M. 1962. Organic micronutrients. In: R. A. Lewin, (Ed.), Physiology and Biochemistry of Algae, New York, pp. 141-159. Emery,.A. R. 1973. Sediments of deep canadian shield lakes: observations of gross structure and biological significance. Science 181:655-657. Felfoldy, L. J. M. and 2. F. Kalko. 1958. The rate of photosynthesis and underwater radiation in Lake Balaton. Observations of summer 1957. Annal. Biol. Tihany 25:304-329. Frear, G. L. and J. Johnston. 1929. Solubilities of calcium carbonate (calcite) in certain aqueous solutions at 25°. J. Amer. Chem. Soc. 51:2082-2093. "i Frey, D. G. 1960. The ecological significance of cladoceran remains in lake sediments. Ecology 41:684-699. Gessner, F. 1939. Die Phosphorarmut der Gewasser und ihre Beziehung zum Kalkgehalt. Int. Rev. ges. HydrObiol. u. o Hydrogr. 35:202-211. Gessner, F. 1959. Hydrdbotanik die physiologischen Grundlagen der Pflanzenverbreitung im wager. II. Stoffhaushalt. VEB Deutscher Verlag Der Wissenschaften. 701 pp. Goldman, C. F. 1963. The measurement of primary productivity and limiting factors in freshwater with carbon-14. 125 Proc. Conf. on primary productivity measure- ment (1961). U.S.A.E.C. TID-7633. p. 103-113. Golterman, H. L. 1969. Methods for chemical analysis of fresh waters. IBP Handbook No. 8. Blackwell Scientific PUblications, London NW1. 172 pp. Golterman, H. L. 1972. The role of phytoplankton in detritus formation. In: Detritus and its ecological role in aquatic ecosystems. ‘kan Ist. Ital. Idrobiol.. 29 Supplz89-103. Hayes, F. R. 1964. The mud-water interface. Oceanogr. Mar. Biol. Ann. Rev. 2:121-145. Heim, A. 1900. Der Schlammabsatz am Grund des Vierwaldstatter Sees. Vierteljahrsschr. Naturforsch. Ges. Zfiridh 45:144-158. Heinemann, H. G., D. L. Rausch, and R. S. Campbell. 1968. Sedimenta- tion in a small channel-type reservoir. Extract of publication No. 71 of the I.A.S.H. Symposium of Garda, pp. 769-779. Hohne, E. und E. Odrich. 1966. Sedimentationstraten. Limnologia 4:313-320. 136 Hutchinson, G. E. 1957. A Treatise on Limnology. Vol. I. Wiley, N. Y., 1015 pp. Jamefelt, H. 1955. Uber die Sedimentation des Sestons. Verh. Internat. Verein. Limnol. 12:144-158. Johnston, J. 1915. The solubility product constant of calcium and magnesium carbonates. Jour. Am. Chem. Soc. 37:2001-2020. Johnston, J. and E. E. Williamson. 1916. The role of inorganic agencies in the deposition of calcium carbonate. J. of Geol. 24:729-750. KleerekOper, H. 1953. The mineralization of plankton. J. Fish. Res. .. Bd. Canada. 10:283-291. 7‘: Kolwitz, R. 1912. Plankton und Seston. Ber. Deut. Bot. Ges. 30:334-336. Kusnezow, S. I. 1966. Die Rolle der Mikroorganismen bei der . . Bildung von Calcitkristallen im Schlemmm des ' Sewan-Sees. Z. Allg. Mikrobiol. 6:289-295. Lawacz, W. 1969. The characteristics of sinking materials and the formation of bottom deposits in a eutrophic lake. Mitt Internat. Verein. Limnol. 17:319-331. Lawacz, W. 1970. Estimation of the energetic value of non-living particulate organic matter (tripton) by two different methods. Pol. Arch. Hydrobiol. 17:135-139. Lean, D. R. S. 1973. Movements of phosphorus between its biologically important forms in lake water. J. Fish. Res. Bd. Can. 30:1525-1536. Lee, G. F. and W. Stunm. 1960. Determination of ferrous iron in the presence of ferric iron with bathophenanthroline. J. Amer. Water Wks. Ass. 52:1567-1574. Leverett, F. and B. B. Taylor. 1915. The pleistocene of Indiana and Michigan and the history of the Great Lakes. U. S. Geol. Surv. Monogr. 53. U. S. Gov. Print. Off., 523 pp. Ludlam, S. D. 1967. Sedimentation in Cayuga Lake, New York. Limnol. Oceanogr. 12:618-632. Manny, B. A. 1971. Interactions of dissolved and particulate nitrogen in lake metabolism. Ph.D. Thesis, Michigan State University. 189 pp. 137 Markham, R. 1942. A.steam distillation apparatus suitable for micro-Kjeldahl analysis. Biochem. J. 36:712-715. McKenzie, H. A. and H. S. wallace. 1954. The Kjeldahl determination ' of nitrogen: a critical study of digestion conditions- temperature, catalyst, and oxidizing agent. Aust. J. Chem. 7:55-70. Menzel, D. W. and J. P. Spaeth. 1962. Occurrence of vitamin B12 in the Sargasso Sea. Limnol. Oceanogr. 7:151-154. Meyers, P. A. and J. G. Quinn. 1971. Interaction between fatty acids and calcite in seawater. Limnol. Oceanogr. 16:992-997. Miller, M. C. 1972. Primary and extracellular production by phytoplankton and its role in carbon cycling in lakes. Ph.D. Thesis, Michigan State University. 212 pp. Mortimer, C. H. 1941-1942. The exchange of dissolved substances between.mud and water in lakes. J. Ecol. 29:280-329; 30:147-201. Moss, B. 1970. Seston composition in two freshwater pools. Limnol. Oceanogr. 15:504-513. Nelsen, F. ML and F. T. Eggertsen. 1958. Determination of surface area adsorption.measurements by a continuous flow method. Anal. Chem. 30:1387-1390. Nipkow, F. 1920. Vorlaufige Mitteilungen fiber Untersuchungen des Schlammabsatzes im.Zurichsee. Z. HYdrol. 1:1-23. Odum, E. P. 1962. Relationships between structure and function in the ecosystem. Jap. J. Ecol. 12:108-118. Odum, E. P. 1963. Primary and secondary energy flow in relation to ecosystem structure. Proc. 16th Int. Congr. 2001. 4:336-338. Odum, E. P. and.A. A. de la Cruz. 1963. Detritus as a major component of ecosystems. Amer. Inst. Biol. Sci. Bull. 13:39-40. Ohle, W. 1934. Chemische und physikalische Untersuchungen norddeutscher Seen. Arch. Hydrobiol. 26:386-464, 584-658. Ohle, W. 1935. Organische Kolloide in ihrer Wirkung auf den Stoffhaushalt der Gewasser. Naturwissenschaften 28:480-484. Ohle, W. 1937. Kolloidgelle als Nahrstoffregulatoren der Gewasser. Naturwissenschaften 29:471-474. 138 Olah, J. 1972. Leaching, colonization and stabilization during detritus formation. lg: Detritus and its ecological role in aquatic ecosystems. ‘Mem. Ist. Ital. Idr0biol. 29 Supp1:105-127. Otsuki,.A. and R. G. wetzel. 1972. Coprecipitation of phosphate with carbonates in a marl lake. Limnol. OceanOgr. 17:763-767. Otsuki, A. and R. G. Wetzel. 1973. Interaction of yellow organic acids with calcium carbonate in freshwater. Limnol. Oceanogr. 18:490-493. Otsuki, A. and R. G. Wetzel. 1974. Calcium and total alkalinity budgets and calcium carbonate precipitation of a small hard-water lake. Arch. Hydrobiol. 73:14-30. Pechlaner, R. 1963. Sedimentation in HOChgebirgsseen. Berichte des Naturwissenschaftlich-MediziniSChen Vereins 53:253-263. Pennington, W. 1974. Seston and sediment formation in five lake district lakes. J. Ecol. 62:215-251. Peters, R. H. and F. H. Rigler. 1973. Phosphorus release by daphnia. Limnol. Oceanogr. 18:821-839. Pia, J. 1933. Kohlensaure und Kalk. Die Binnengewasser. B. 13. Stuttgart, Schweiz. Verlags. 183 pp. Provasoli, L. 1963. Organic regulation of phytoplankton fertility. 13;: The Sea, Vol. 2. M. N. Hill (Ed). New York. pp. 165-219. Rainwater, F. H. and L. L. Thatcher. 1960. Methods for collection and analysis of water samples. U. S. Geol. Surv., water Supply Paper: 1454. 297 pp. Reissinger, A. 1932. Quantitative Untersuchungen fiber den Schlammabsatz im Alpsee, dem Niedersonthofener See und dem Starnberger See. Arch. Hydrdbiol. 24:535-542. Rich, P. H. 1970a. Utilization of benthic detritus in a.mar1 lake. Ph.D. Thesis, Michigan State University. 78 pp. Rich, P. H. 1970b. Post-settlement influences upon a southern Michigan marl lake. Mich. Bot. 9:3-9. Rodina, A. G. 1967. Variety and destruction of lake detritus. Verh. Int. Ver. Limnol. 16:1513-1517. Rossolimo, L. 1937. Materialy k poznaniyu sedimentatsii ozernykh otlozhenii (in Russian, German summary). Trudy Limnologischeskoi Stantsii v Kosine. pp. 1-21. ' -tu \.' ' a" .‘F f' 139 Ruttner, F. 1921. Das elektrolytische Leitvermogen verdfinner Losungen unter dem Einfluss submerser Gewachse. Siz. Ber. Akad. d. Wiss. Wien, math. Naturw. K1.I/130. (As cited by Ruttner 1963). Ruttner, F. 1963. Fundamentals of Limnology. Univ. Toronto Press. 295 pp. ’ Saunders, G. W. 1957. Interrelations of dissolved organic matter and phytoplankton. Botanical Rev. 23:389-410. Schelske, C. L. 1962. Iron, organic matter, and other factors limiting primary productivity in a marl lake. Science 136:45-46. Schelske, C. L. and E. Callender. 1970. Survey of phytoplankton productivity and nutrients in Lake Midhigan and Lake Superior. Internat. Assoc. Great Lakes Res. Proc. 13th Conf. Great Lakes Res. 93-105. Scott, W. and D. H. Miner. 1936. Sedimentation in Winona Lake and Tippecanoe Lake, Kosciusko County, Indiana, July 31, 1930, to July 30, 1935. Proc. Ind. Acad. Sci. 45:275-286. Shapiro, J. 1969. Iron in natural waters - its characteristics and biological availability as determined with the ferrigram. verh. Int. ver. Limnol. 17:456-466. Sheldon, R. W. 1972. Size separation of marine seston by membrane and glass-fiber filters. Limnol. Oceanogr. 17:494-498. Sokal, R. R. and F. J. Rohlf. 1969. Biometry the principles and practice of statistics in biological research. W. H. Freeman and Co., San Francisco. 776 pp. Steemann Nielsen, E. 1951. .Measurement of the production of organic matter in the sea by means of carbon 14. Nature 167:684-685. Steemann Nielsen, E. 1952. The use of radio-active carbon (C14) for measuring organic production in the sea. J. Cons. Int. ' Expl. Mer. 18:117-140. Steidtmann, E. 1935. Travertine-depositing waters near Lexington, Virginia. Science 82:333-334. Strickland, J. D. H. 1960. Measuring the production of marine phytoplankton. Bull. Fish. Res. Bd. Canada 122:1-172. Strickland, J. D. H. and T. R. Parsons. 1972. .A practical handbodk of seawater analysis. Bull. Fish. Res. Bd. Canada, 167, 310 pp. Suess, E. 1968. Calcium carbonate interaction with organic compounds. Ph.D. Thesis, Lehigh University. 154 pp. 140 - Suess, E. 1970. Interaction of organic compounds with calcium carbonate. 1. association phenomena and geochemdcal implications. Geochim. Cosmochim. Acta 34:157-168. Sushenya, L. M. 1968. Detritus and its role in.the production processes of waters. Hydrdb. J. 2:77-83. Talling, J. F. 1971. General outline of spectrophotometric methods. Pages 22-25, In: R. A. Vollenweider, Ed. A manual on methods for measuring—primary production in aquatic environments. IBP Handbook No. 12. Blackwell Scientific Publications, London NW1. 213 pp. Thomas, E. A. 1950. Beitrag zur Methodik der Produktionsforschung in Seen. Schweiz. z. Hydrol. 12:25-37. Thomas, E. A.” 1951. Produktionsforschungen auf Grund der Sedimente im Pfaffikersee und Zurichsee. verh. Int. ver. Limnol. 11:409-421. Thomas, E. A. 1955a. Sedimentation in oligotrophen und eutrophen Seen als Ausdruck der Produktivitat. ‘verh. Int. ver. Limnol. 12:383-393. Thomas, E. A. 1955b. Stoffhaushalt gnd Sedimentation im oligotrophen Aegerisee und im eutrOphen Pfaffiker- und Greifensee. WEmL Ist. Ital. Idr0biol., Suppl. 8:357-465. Thomas, E..A. 1956. Sedimentation und Stoffhaushalt imvTfilersee. Monatsbullegin des Schweizerischen vereins von Gas- und wasserfachmannern 12:1-11. Tutin, W. 1955. Preliminary observations on a year's cycle of sedimentation in Windermere, England. Mem. Ist. Ital. Idrobiol., Suppl. 8:467-484. walton, A. G. 1967. The formation and properties of precipitates. Interscience Publishers. New York. 232 pp. wetzel, R. G. 1964. A comparative study of the primary productivity of higher aquatic plants, periphyton, and phytoplankton in a large, shallow lake. Int. Rev. ges. Hydrdbiol. 49:1-61. Wetzel, R. G. 1965. Techniques and problems of primary productivity measurements in higher aquatic plants and periphyton. Mam. Ist. Ital. Idr0biol., Suppl. 18:249-267. Wetzel, R. G. 1966a. Productivity and nutrient relationships in marl lakes of northern Indiana. verh. Int. ver. Limnol. 16:321-332. wetzel, R. G. 1966b. variations in productivity of Goose and hypereutrophic Sylvan Lakes, Indiana. Invest. Indiana Lakes Streams 7:147-184. 141 Wetzel, R. G. 1968. Dissolved organic matter and phytoplanktonic productivity in marl lakes. IMitt Int. Ver. Limnol. 14:261-270. Wetzel, R. G. 1972. The role of carbon in hard-water marl lakes. In: G. E. Likens (Bd.) Nutrients and Eutrophication. Amer. Soc. Limnol. Oceanogr. Symp. Ser. 1:84-97. Wetzel, R. G. 1973. Productivity investigations of interconnected marl lakes. 1. the eight lakes of the Oliver and walters chains, Northeastern Indiana. Hydrobiol. Stud. 3:91-143. Wetzel, R. G. and H. L. Allen. 1972. Functions and interactions of dissolved organic matter and the littoral zone in lake metabolism and eutrophication. In: Z. Kajak, and Hillbricht- Ilkowska (Eds.) Productivity Prablems of Freshwaters, warsaw 1970. Proc. IBP-UNESCO Symp. Pol. Acad. Sci. pp. 333-347. Wetzel, R. G., P. H. Rich. M. C. Miller and H. L. Allen. 1972. Metabolism of dissolved and particulate detrital carbon in a temperate hard-water lake. In: Detritus and its ecological role in aquatic ecosystems. _FEmL Ist. Ital. Idrdbiol. Suppl. 29:185-243. White, W. S. and R. G. Wetzel. 1973. A.modified sedimentation trap. Limnol. Oceanogr. 18:986-988. Wiebe, W. J. and L. R. Pomeroy. 1972. Microorganisms and their association with aggregates and detritus in the sea: a microsc0pic study. In: Detritus and its ecological role in aquatic ecosystems. -kan Ist. Ital. Idrobiol. Suppl. 29:105-127. Wilson, I. T. 1936. .A study of sedimentation of Winona Lake. Proc. Ind. Acad. Sci. 45:295-304. Wood, K. G. 1974. Carbon dioxide diffusivity across the air-water interface. Arch. Hydrobiol. 73:57-69. “mum