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Data were gathered on the distribution of phytOplanktonic numbers, volumes, composition, structure, and productivities in near shore waters of western Lake Erie, a man—made embayment, and a polluted river. Samples for population estimates were collected at monthly intervals. Pri- mary productivity was estimated usually twice per month using the L—D bottle oxygen method. Nearly 200 species of phytoplankton were observed during the study, the majority of which were common to all areas investigated. Negligible vertical population differentiation was found within stations during the investigation. Greatest numbers were observed in the Spring, but greatest phytOplanktonic volumes were observed in late summer. Spring pOpulations, dominated by diatoms, were displaced during the summer by increasing percentages of green and blue-green algae. The rate and composition of the succession varied among the sampling stations. Greatest species diversities COmmonly occurred at the inshore areas. Most frequently the lowest equitability was found in the river. Least phytOplanktonic volumes, blue-green algal volumes, mean individual volume, and primary productivities were generally observed in the river. Greatest phytOplanktonic numbers, volumes, and productivities, as well as volumes of diatoms and green algae were most frequently observed in Michael D. Marcus the man-made embayment. The lake was generally observed to be inter— mediate in most categories but usually had the least community res- piration. Water temperatures appeared to be a major factor regulating class composition in the spring and late fall. Light appeared to influence phytOplanktonic productivity through photoperiod variation and limited light penetration. Productivity in the embayment closely followed photOperiod. Wind induced turbulence helped to increase the turbidity in the area, reducing light penetration so that little productivity occurred below 1 m. The high turbulence in the lake also appeared to effect a reduction of productivity by causing a disorientation of the plant cells. Neither phosphorus nor carbon concentrations seemed to - limit productivity during the study, however phosphate concentrations did pulse with the blue-green algae bloom in the lake. Nitrogen con- centrations appeared to be related to seasonal successional patterns in the dominant classes, especially the blue-green algae. Grazing pressure by the zooplankton may have suppressed phytOplanktonic abundances while effecting an increase in the mean individual size of the populations. The level of primary productivity indicated that the area is in a highly eutrophic state as a result of man induced nutrient enrichment. The area was observed to be nearly exclusively heter- otrOphic. Most of the sestonic community respiration probably is non-phytOplanktonic in nature. Analysis of the data suggests that increased nutrient enrichment leads to decreased mean individual sizes of the phytOplankton and increased species diversities; these rela- tionships contrast with results obtained in earlier ecological studies. THE DISTRIBUTION OF PHYTOPLANKTON AND PRIMARY PRODUCTIVITY NEAR THE WESTERN SHORE OF LAKE ERIE By Michael D. Marcus A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Fisheries and Wildlife 1972 57A DEDICATION This thesis is dedicated to the ideal of world peace through world unity. ii ACKNOWLEDGEMENTS I would like to express my appreciation to Dr. R. A. Cole for his help throughout this study and aid in preparation of the manu— script. Appreciation is also expressed to my graduate committee members, Drs. N. R. Kevern, C. D. McNabb, and R. G. Wetzel, for their valuable advice and prompt review of the manuscript. Special thanks is extended to my fellow graduate students, especially to B. R. Parkhurst and T. F. Nalepa for their assistance with field work. My deep gratitude is expressed to my parents and friends for their continuing support, encouragement and inspiration. This study was supported by the Detroit Edison Company and the Institute of Water Research. Use of the Michigan State University Computer Laboratory was made possible, in part, through the partial support of the National Science Foundation. iii TABLE OF CONTENTS INTRODUCTION . DESCRIPTION OF STUDY AREA MATERIALS AND METHODS Field Procedures . . . Laboratory Procedures . Experimental Analysis . RESULTS . . . . . . . . PhytOplankton Abundance . Spatial variation Total numbers and volume Volumes by class Seasonal variation . . Total numbers, volumes, and carbon Class dynamics Species dynamics Phytoplankton Diversity and Equitability Community Metabolism . DISCUSSION . . . . . . . . . Diurnal Productivities and Community Respiration Regulation of Abundance and Productivity Community Structure . LITERATURE CITED . . . . . APPENDIX . . . . . . . . . . iv Page l4 l4 l5 l7 l9 l9 l9 19 21 22 22 25 25 42 55 65 65 67 73 76 81 Table A1. A2. ’ A3. LIST OF TABLES Meteorological conditions on days primary productivity estimates were made including each month's means (M.M.) (U.S. Dept. of Commerce, 1970) . . . . . . . . . . . . . . . . . . . . . Means by sampling stations of numbers, volumes, mean individual volumes, and class volumes for all dates sampled during the study . . . . . Species found during study listed by class with corresponding mean annual species volumes (D3). Number of species found on each date and the annual means by station . . . . . . . . . . . . Mean diversities and equitabilities at the sampling stations during the study period . Mean community respiration (mgC/mZ/hr) estimated during productivity incubation at the sampling stations (x 1 1 SE) . . . . . . . . . . . . . . Estimated mean seasonal gross primary produc— tivity of the phytOplankton at the sampling stations . . . . . . . . . . . . . . . . . Ratios of mean daily phytOplanktonic gross primary productivity to community respira— tion (P/R) at the sampling stations . . . Phytoplankton density (no/ml) arranged in order of increasing abundance at the sampling stations . . . . . . . . . .'. . . . . . . . . PhytOplankton volume (x104 u3/ml) arranged in order of increasing abundance at the sampling stations . . . . . . . . . . . . . . . . . Mean individual planktonic volume (U3) arranged in order of increasing volume at the sampling stations . . . . . . . . . . . . . . . . . . Page 13 20 45 51 55 63 66 68 81 83 85 Table A4. A5. A6. A7. A8. Volume (x103 u3/ml) of blue-green algae arranged in order of increasing abundance at the sampling stations . . . . . . . . . . . . . . . . . . . . Volume (x103 u3/m1) of green algae arranged in order of increasing abundance at the sampling stations . . . . . . . . . . . . . . . . . Volume (x103 u3/m1) of diatoms arranged in order of increasing abundance at the sampling stations Mean diversity of phytoplankton arranged in order of increasing diversity at the sampling stations Mean equitability of phytoplankton arranged in order of increasing equitability at the sampling stations . . . . . . . . . . . . . . . vi Page 87 89 91 93 95 Figure 10. ll. 12. LIST OF FIGURES Map of the study area in relation to western Lake Erie O C O I O O O O O I I O O O O O O 0 Map of the study area including positions of the sampling stations . . . . . . . . . Mean numbers, volumes, and carbon contents of phytOplankton by stations . . . . . . . Mean volume of phytoplankton organisms by station . . . . . . . . . . . . . . . . Mean seasonal variation in volumetric com- position of phytoplankton classes at the sampling stations during the study Seasonal dynamics by volume of Melosira granulata and Stephanodiscus astraea at the sampling stations . . . . . . . . . . Seasonal dynamics by volume of Stephano- discus binderanus and S, niagarae at the sampling stations . . . . . . . . . . . . . . Seasonal dynamics by volume of Coscino- discus radiatus and Anacystis cyanea at the sampling stations . . . . . . . . . . . Seasonal dynamics by volume of Anacystis elachestra var. conferta and A, incerta at the sampling stations . . . . . . . Seasonal dynamics by volume of Aphanizomenon flos-aquae and Oscillatoria'sp. at the sampling stations . . . . . . . . . . Seasonal dynamics by volume of Coelastrum sphaericus and Pediastrum duplex at the sampling Stations I O O O I O D O O O O O O O O O O O 0 Mean diversity and equitability of phytoplank- ton by station on each sampling date . . . . . vii Page 24 27 29 32 34 37 39 41 44 54 Figure 13. 14. 15. Mean gross primary productivity (R i 1 SE) es- timated during midday incubation periods . . . Profiles of average gross primary productivity over the study period . . . . . . . . . . . Diurnal primary productivity in the lake and discharge canal on 1 July 1970 . . . . . . viii Page 57 6O 62 INTRODUCTION The purpose of this paper is to examine and compare the phyto- plankton populations and associated primary productivity of near shore areas in western Lake Erie to two shoreline areas in order to determine distributional variations in population parameters. This investigation was conducted as part of a comprehensive ecological study undertaken to provide base-line information on which the heated water discharges from a new fossil fuel steam electric plant could be evaluated. Information on the distribution of environmental para- meters that can potentially influence phytoplankton distributions have been obtained through that study. Lake Erie has historically been the receptacle of urban and industrial effluents. Vorce (1882) recognized the potentially ad- verse effects of waste disposal to Lake Erie nearly a century ago. Subsequently, continual use of the lake as a waste depository has created many habitat and chemical alterations that have, in turn, brought about biotic changes in the lake (Carr, 1962; Davis, 1964). Currently, Lake Erie is considered highly eutrOphic. This is in many respects particularily true of the shallow western basin which receives the largest concentrations of effluents via the Detroit and Maumee rivers (Powers and Robertson, 1966). Some fear has been ex- pressed that the high concentrations of waste in Lake Erie under certain periodic meteorological conditions will result in an unpre- cedented mortality to resident aquatic organisms (Carr, 53.51., 1965). 2 Under extended periods of calm, hot weather, stratification of the lake can result in severe anaerobiosis from decomposition of discharged waste organic material and settling plankton. PhytOplankton are responsible for nearly all of the primary pro- ductivity in the western basin because of limited light penetration and suitable substrate for benthic plants (Chandler, 1944). It is believed that limited competition for nutrients and massive daily additions to the dissolved nutrient load yields phytOplankton pOpu— 1ations capable of supporting very large animal communities (Gottschall and Jennings, 1933). Continual nutrient enrichment has resulted in consistent increases in annual phytOplankton crops (Arnold, 1969) with the classical annual bimodal biomass patterns becoming less noticeable (Michalski, 1968; Davis, 1969), a result of the increasing eutrophic conditions. The regulators of phytOplanktonic productivity that stand out most commonly as limiting factors are levels of various nutrients, toxicants, light, temperature, and grazing by secondary producers. Most often limiting in freshwaters are nutrient concentrations. Among the macronutrients, low phosphorus, nitrogen and carbon levels are frequently associated with limited productvity (Deevey, 1972). Less frequently, various micronutrients also have been observed in quantities sufficiently low to limit algal productivity (Goldman, 1972). Light and temperature tend to define the limits of seasonal productivity, particularly in the winter (Verduin, 1956). Consequently, under most natural conditions, when no other limiting condition exists, maximum seasonal productivity would be expected when temperature and light were maximum, i.e., during the summer. Within the confines of these limiting factors, the composition and accumulation of phytoplankton can 3 be further regulated by grazing pressure, primarily from the zooplankton (Brooks, 1969). DESCRIPTION OF STUDY AREA The western basin of Lake Erie has an average depth of 7.3 m, with a surface area of 3,276 km2 (Carr, et_al., 1965). The Detroit River discharges into the western basin at about 5000 m3/sec and accounts for 95% of the inflow to the lake (Casper, 1965). This inflow delivers approximately 97,500 metric tons of nitrogen and 42,600 metric tons of phosphorus to the lake each year (conversions from Harlow, 1966). Water from the Detroit River flows southward into the western basin and con— tributes with wind variation to the formation of discontinuous clockwise eddy currents in the Toledo-Detroit area (Hartly, et_al., 1966). As a result, northeastward currents prevail along the Michigan shore. The western basin has a flow—through time of about two months and the entire lake about three years (Verduin, 1969). Stations selected for study of the near—shore phytoplankton of Lake Erie centered on the mouth of the River Raisin at Monroe, Michigan (Figure 1). Three lake stations were positioned approximately parallel to the prevailing north-easterly current (Figure 2): one about 5 km north of the mouth of the river and 1.5 km from shore (station 1); one about 1.0 km east of the river mouth (station 3); and the last south of the mouth about 10.5 km and 3 km from the shore (station 6). Bottom sediments of the north lake station range from course gravel to silt and clay, station 3 is predominantly sand, and the south lake station is primarily silt and clay. Two inshore stations were selected for comparison with the lake (Figure 2). A discharge canal (station 8), 2.5 km long by 150 m wide, 4 Figure 1. Map of the study area in relation to western Lake Erie. Figure 2. Map of the study area including positions of the sampling stations. le § Prevailing current 0 Plankton P Primary productivity 9 was constructed during 1969-1970 to carry cooling water effluent from the steam electric plant. During this study, no water flowed through the discharge canal. It was essentially an embayment of Lake Erie, in which water freely exchanged with the lake during storms and seiches. A minute flow (< l m3/sec) from Plum Creek, a tributary also contributed to the discharge canal. Bottom composition of the 6-7 m deep dredged canal was silt, clay and plant debris (mainly of marsh origin). The second inshore station (station 9) was located in the highly polluted River Raisin. The river receives primarily treated municipal wastewater and papermill wastes from Monroe, Michigan. A putty-like sediment combined with paper fiber and traces of oil make up the river bottom. Depths of 6—7 m are maintained in the river by annual dredg- ing. Mean river discharge, measured by the U.S. Geological Survey during 1970, was 17 m3/sec, but varied from a high mean monthly discharge in the spring (41.9 m3/sec) to the low mean monthly discharge in the summer (3.3 m3/sec). Chemical and physical conditions of the study area during the study period are presented in detail by Nalepa (1972) and Cole (1972). A brief summarization of pertinent observations follows. Water tempera- tures varied uniformly among the three lake stations which differed only slightly from the inshore stations in the spring. During early May temperatures in the lake were 1238 to 15 C, 17 C in the discharge canal and about 14 C for the river. Maximum temperatures for all five stations were reached in August (about 25 C). Thereafter, the tempera— tures dropped steadily. Ice formed along the shore in December and by the middle of January an ice pack had formed in Brest Bay. Seasonal fluctuations in oxygen were similar for all stations with the exception of the river which was always lower. Maximum oxygen 10 concentrations occurred in early May, ranging from 9 mg/liter in the lake to 5.5 mg/liter in the river. Concentrations decreased to the minima recorded on 11 October 1970 with 4 mg/liter found in the lake to 0.5 mg/liter in the river. In late October the oxygen concentrations began to rise sharply in a delayed response to seasonal cooling. Highest nitrate-nitrogen concentrations (> 5.0 mg/liter) were observed for all parts of the study area in the Spring and lowest concentrations (m 0.02 mg/liter) in August and September. Concentra- tions then gradually increased into winter. River concentrations were significantly higher (p < 0.05) than the rest of the area about half of the time during the spring and consistantly higher (p < 0.05) during the entire summer. Total phosphorus concentrations fluctuated sporadically during the study. Most stations had lowest concentrations during the spring and early summer. A notable pulse occurred at most stations in August. Consistantly higher concentrations (p < 0.05) were found throughout the study in the river, with intermediate concentrations observed in the lake and discharge canal. Similar seasonal changes in sestonic organic carbon (> 0.45 u) occurred at all stations during the study. Highest concentrations occurred in May. The concentrations decreased then fluctuated until late August when another peak developed. Concentrations averaged con— sistantly lower in the lake, with the inshore areas averaging 3-12 mg/liter higher. SuSpended solids (seston), consisting mainly of detritus, re- suspended bottom material, and plankton, represents the total particu- late material (> 0.45 p) in the water. The Maumee and Detroit rivers deliver large quantities of suspended material to Lake Erie, the bulk 11 of which remains in the western basin (Pinsak, 1967). This material essentially remains in suspension, through wind generated turbulence, and contributes to the low light penetration observed by Verduin (1969) to be less than 5% at l m. During 1970, the seston had three definite peaks at the lake sta- tions: 15 May, 63 mg/liter; 4 August, 36 mg/liter; and 15 September, 33 mg/liter. Little variation was encountered between the lake stations but inshore values were generally about twice those of the lake. Much of the detritus in the water during the early months of the study had as its source the irregular dredging activities in the discharge canal and during the later summer months the dredging of the River Raisin shipping channel. At no time during this study did the secchi disc reading at any station exceed 1 m. L Zooplankton distributions were found to be generally uniform among the lake stations which differed from the inshore stations (Nalepa, 1972). Highest biomass occurred at the lake stations while highest densities occurred in the discharge canal. The river had the lowest density and biomass. Although the density and biomass differed widely among the lake and inshore areas the species composition was essentially the same. Parkhurst (1971) investigated the fish populations concurrently with this study and found an uneven distribution throughout the study area. The greatest density and biomass of fish occurred in the dis- charge canal. For most of the study, the river was devoid of fish. Various weather parameters on the days for which primary pro- ductivity estimates were made are given in Table 1. Observations were made at the Toledo (Ohio) Express Airport (U.S. Dept. of Commerce, 12 1970). Climatic conditions on sampling days were generally repre- sentative of the typical seasonal conditions experienced. 13 Table l. Meteorological conditions on days primary productivity estimates were made including each month's means (M.M.) (U.S. Dept. of Commerce, 1970). 2 Sky Cover Date Z Possible (Sunrise to Average Wind Mean Air 1970 Sunshine Sunset) Wind (Km/hr) Direction Temperature 5/1 0 100 27.4 sw 18.9 5/15 52 60 15.3 SW 20.0 5/27 53 70 17.7 W 13.9 M.M. 52 63 16.3 W 16.2 6/10 28 80 10.1 S 23.3 6/23 100 10 8.9 S 18.9 M.M. 66 58 13.8 W 19.6 7/7 92 50 13.0 SW 21.1 7/21 98 20 11.1 NW 16.1 M.M. 63 68 12.9 NW 21.8 8/4 95 50 9.5 NW 16.1 8/24 86 30 .0 W 18.9 M.M. 73 46 11.1 E 20.8 9/1 91 30 6.4 NE 14.4 9/29 59 70 10.9 SW 7.8 M.M. 53 69 12.6 W 17.8 10/27 25 80 15.9 E 15.6 M.M. 49 63 14.2 12.2 MATERIALS AND METHODS Field Procedures Samples for phytOplankton pOpulation analysis were collected at four week intervals from 1 May 1970 to 7 November 1970. Additional population data were collected on 23 January 1971 and 18 February 1971. Primary productivity estimates were made during the ice free season of this period at three of the stations (3, 8, 9) at approximately bi- weekly intervals when possible. Duplicate samples from each of two depths, 0.5 and 2.5 m, were collected from each station for population analysis. The lake stations were marked with buoys and the duplicate samples taken about 150 m east and west of each buoy. Inshore stations were identified from on-shore reference points and the duplicate samples were taken about 65 m apart. Samples were collected with a clear, Plexiglas, 8.1 liter Van Dorn water bottle. From each sample 500 ml were pre- served with 1.5% solution of formalin (Weber, 1968). The remaining 7.6 liters were analyzed for zOOplankton (Nalepa, 1972) and water chemistry (Cole, 1972). Samples for estimation of primary productivity were collected with a 4.1 liter PVC Van Dorn water bottle. Samples were taken from the surface, 0.5, 1.5, and 2.5 m. The water from each level was delivered by gravity flow from the water bottle to two 300 ml DO light bottles and two dark bottles, formed by double wrapping 300 ml DO bottles with black plastic tape. The dark bottles were painted white to prevent their excess heating from solar radiation. Foil caps, secured by a rubber l4 15 band, were placed on the stoppers of the dark bottles after filling. When the four bottles from a specific depth were filled, they were attached to a suspension rod and hung from an incubation float at the depth from which the sample was drawn. On most occasions the tro- pholytic zone of the three stations occurred at 2.5 meters at all three stations. Ig_§i£u incubation of the samples was conducted for approximately a four hour interval over the noon period, inorder to obtain estimates from the periods of maximum photosynthetic activity (Morgan and Strass, 1969; Vollenweider, 1969). Gross primary productivity estimates were made by the change in oxygen method (Strickland, 1960). Oxygen concentrations were deter- mined prior to and upon completion of the incubation. Analysis of oxygen on 15 May, 27 May, 10 June, and 27 October were completed using the Winkler dissolved oxygen test. 0n the remaining dates a Yellow- Springs Model 51A oxygen meter with self-stirring probe was used. The meter was periodically standardized against Winkler determinations. Dawn to dusk primary productivity estimates were made on 1 July 1970. The estimates were made over four time intervals in the lake (station 3) and discharge canal (station 8). Laboratory Procedures Population samples were returned to the laboratory for enumera- tion by the membrane filter method described by McNabb (1960) and recently adopted by Standard Methods (A.P.H.A., 1971). Briefly, a 5 to 40 m1 aliquot of the 0.5 liter phytoplankton population sample, de- pending on population concentration, was filtered through a 2-inch filter (type HA, 0.45u). The filter was placed on a 2x3 inch 16 microsc0pe slide, coated with emersion oil for clearing the filter, and stored horizontally in the dark until enumerated. The filters were examined with a dark phase microsc0pe at 200x and 430x. The fre- quency-occurence of each species was calculated from observations made in 30 fields from each filter. Conversion from the number of occurrences of a species observed in the 30 fields to its density per milliliter was based on the formula given by McNabb (personal communication), modified to fit this study's data: no./ml= d x 109 (microsc0pe quadrant area in NZ) x (ml filtered) where d, based on frequency occurrence, is found in a table in McNabb's (1960) paper. Identification on the filters was impossible for most species of. unicellular centric diatoms, many species of pennate diatoms, species of the diatom genus Melosira, and the genera Aphanizomenon and Oscilla— tgria, PrOportional counts were made of apprOpriate mounts. These results were applied to the total counts of the undistinguishable taxa from the filters to determine their respective abundances. Material for proportional diatom counts was prepared according to Weber (1970), except that combustion of the organic material was accomplished in a muffle furnace at about 540° C for 30 minutes. Mounts of diatoms were made with hyrax (Hanna, 1930). The genera of Aphanizomenon and Oscillatoria were identified from separate wet mounts of the material and the proportions determined were applied to the total counts of the two genera on the appropriate filter. At no time was there noticeable numbers of dead plant cells in fresh samples as observed by Verduin (1951), therefore, no effort was made to eliminate dead material in the counts. l7 Species identifications were made through use of keys by Tiffany (1934, 1937), Taft (1942, 1945, 1964), Taft and Kishler (1968), Prescott (1962, 1970), Weber (1966), Hustedt (1930), Patrick and Reimer (1966), and Hohn and Hellerman (1963). Revisions in classification are accord- ing to Palmer (1962). Aid in the general identification of phytop- lankton, especially diatoms, was given by Mr. B. H. McFarland and Dr. C. I. Weber of the Analytical Quality Control Laboratory, EPA, Cincin- nati, Ohio. More specific taxonomic problems were referred to Dr. C. D. McNabb, Michigan State University. Biomass determinations were completed by making random measure- ments (generally > 10) of each species, throughout the sampling period, with a Whipple micrometer (Welch, 1948). The annual means of these measurements for each species were calculated and applied to geometrical solids that most closely resemble the species' shape to determine their average annual volume for the cell, colony, or filament. With those species where insufficient measurements were made, values for computing volumes were obtained from the literature. Experimental Analysis Two—way analysis of variance was applied to the population data gathered on each date to assess vertical (depth) and horizontal (station) differences. The parameters analyzed included total numbers, total biomass, numerical diversity, numerical equitability, volumetric diversity, volumetric equitability, mean individual species volume, CyanOphyceae (Blue-green algae) volume, ChlorOphyceae (green algae) volume, and Bacillariophyceae (diatom) volume. Tukey's multiple comparison test (Mendenhall, 1968) was used to identify significantly different (p < 0.05) values when the analysis of variance indicated that differences existed. 18 All statistical calculations were based on the per milliliter values calculated from the original frequency occurrence obtained during microscopical analysis. Diversity was calculated by the Shannon formula, S d=—ZN.1og2N _1 __i_, i=1 N N and equitability, or uniformity of species composition, by E=2d, _N being the total number 0f individuals observed,__N_i being the number of individuals in the ith species and §_being the total number of species (MacArthur, 1965). Since no difference was found in the vertical distribution at the' stations, a phenomenon observed by others for Lake Erie (Chandler, 1940; Verduin, 1951; Hintz, 1955), the data obtained in the four replicates at each station are presented as means for the station. From means for total numbers and total biomass, conversions to total phy- tOplanktonic carbon content were made using appropriate formulae from Strathmann (1967). The primary productivity data were interpolated to estimate the productivity and respiratory rates for the 1 and 2 m intervals. Dupli- cate data for the same levels at the station were averaged to determine metabolic activity of the column under a square meter. Oxygen concen- trations were converted to carbon concentrations using the carbon to oxygen ratio, 0.312, as suggested by Westlake (1969). RESULTS PhytOplankton Abundance Spatial variation Total numbers and volume: Virtually no differences in numbers or volumes were detected between depths during the study but differences among stations occurred frequently (Appendix, Tables Al and A2). Differences among stations on any particular date were as much as an order of magnitude, but relative abundances among stations often changed from one sampling date to the next. However, some consistant trends are recognized. The river (station 9) consistently had the smallest volume of phytOplankton, being significantly lower (p < 0.05) than the stations with the greatest abundance on 87.5% of the dates. Numbers of the phytoplankton in the river, however, did not consistently rank lower or higher than other stations. In the discharge canal (station 8) both numbers and volumes of phytoplankton were significantly greater than stations with the least abundance of many (62%) of the dates sampled. These observations are reflected in the annual averages presented in Table 2. Volumes were greatest in the discharge canal, intermediate in the lake, and least in the river. Numbers were also greatest in the discharge canal, while highly variable among the lake stations. The average of all lake stations was similar to average river numbers of phytOplankton. The relative ranking of volumes and numbers at the stations indi— cate that the river had the smallest mean individual phytoplankton l9 20 com cm ofiq mmm.m mwo mmma o Nmm Nos eHoH mow.k aqua wmem w HNN mm mNHH mmm.oH omen msoH e mmm was QAHH AwH.OH mmma Nmma m Nam No «we mwm.a Name . NOON H AHE\41 OH xv AHE\m41 OH xv AHE\ 41 OH xv A «a mmEDHo> AHE\ 41 OH xv mmEDHo> AHE\.ocV muonEDZ cowumum we: o> «Esmo> megmo> mmswflbfich m q cams awe: Seumfim ammuo ammuwIOSHm cmmz cmmz :mm: cme .kpsum axe wawuso pmHmEmm mmump Ham How mmEDHo> mmmao can .mmEDHo> Hmspfl>wpcfl came .mmEDHo> .muwnesa mo cofiumum wawaaEmm ma mane: .N mammH 21 volumes. The average size of the river's phytOplankton was consis- tently lower than at the remaining stations (Appendix, Table A3). None of the remaining stations had consistently greater mean individual volumes than other stations in this study. Volumes by class: Class composition by volume varied among stations while vertical distribution remained uniform. The river consistently had a lower volume of blue—green algae than the other stations (Appendix, Table A4). This was reflected in low annual means for the river as well (Table 2). There was a tendency for blue- greens to be more abundant most frequently in the discharge canal but not much more frequently than in the lake. Both green algae (Appendix, Table A5) and diatoms (Appendix, Table A6) were more abundant by volume in the discharge canal when there were identified (p < 0.05) differences in abundances among the stations. Significant differences occurred on about half of the dates sampled. The tendency for greater abundances in the discharge canal is reflected in the annual mean volumes (Table 2). The relative volumes in the lake and river varied from date to date. No consistent differ- ences were observed between the two areas, although annual means were slightly lower in the river than in the lake (Table 2). Phytoplankton in classes other than the three major classes dis- cussed above played a minor role in the near and inshore waters of Lake Erie in 1970. Euglenophyceae, primarily Euglena sp., made up 1% of the volume of the south lake station and 10% in the discharge canal during May. Ceratium hirundinella, a dinOphycean, accounted for 4 to 6% of the phytOplanktonic volume in the lake during late July. This species made an appearance (3% by volume) in the discharge canal almost two months later and was never important in the river (< 1%). 22 Seasonal variation Total numbers, volumes, and carbon: Seasonal changes in phyto— plankton numbers, volumes, and carbon content were fairly uniform throughout the study area (Figure 3). Remnants of a spring phytoplank— ton bloom were detected at the north lake and river stations when sampling began on 1 May 1970. The maximum density of phytOplankton found in the lake (2530/ml) was recorded at that time. The maximum density (6333/m1) found at any station during the study occurred in late June in the discharge canal. A summer minimum occurred in late July in the lake and discharge canal. After that period the abundances increased at all stations to bloom proportions (mid-August). At this time the maximum phytOplanktonic volumes were recorded for the lake 7 u3/ml) and the river (2.08 x 107 p3/ml). After the bloom, (7.38 x 10 phytoplankton volumes, numbers, and carbon sharply declined to low fall concentrations. Winter phytOplankton concentrations were much lower than concen- trations found for the other seasons. Near the north lake station on 23 January 1971, shortly after safe ice formed, a mean volume of 1.40 x 106 p3/ml was observed with a mean count of 438/m1. When sampled three weeks later on 18 February 1971 the volume in the lake had decreased to a mean of 1.85 x 105 u3/ml with an average number of 147.5/ml. The discharge canal had similar concentrations at this time: a mean volume of 2.11 x 105 u3/ml and a mean number of 327/m1. Carbon concentrations changed generally like the volumes and numbers (Figure 3). However, planktonic carbon concentrations were prOportionally lower in the spring and fall than numbers and volumes and proportionally higher during summer. Explanation for these variations are revealed when seasonal changes of the major classes are considered. 23 Figure 3. Mean numbers, volumes, and carbon contents of phytoplankton by stations. numbers; ----- volumes; —.-.- carbon. (l/Dw) uoqmg I0101 —q J .q 2'5 -f'5L’5I-‘fl .— 0 .<-.:\:\\ O 4 -r~l‘ N 3 \.\“\ 9 E 3 O m l 1 J 1 1 1 1 1 Q 07 co rx (.0 Ln tr m N —~ 0 (um/g TQOIX) awnIOA 10:01 PUD (IUJ/gOlX) NQUJUN [moi (I/bw) uoqwo losOI LO m '1‘ M N r I I *‘r v F; M V -w—‘va’zs'gu’. O o< 01" ‘3 ‘\7‘~c o -' .Q\\‘\ I“ 0 . i“ m G E 2 | l 1 1 1 1 1 1 9 O) (D rs u) to :3 r0 (Iw/gfl‘OIX) °WM0A moi PUD (IW/gOIX) “OwnN |°I°l (|/bu1)uoqm:)|o;ol w n v m N _ o I I I I I I ILL ; 1 ch 0 .K O -’ o c r~ t m o —- z L;_L 1 g m (D (lW/g’umm ownIOA 10:01 puo (lW/gOlX) JaqumN “3101 (I AM) uoqaog ”no; (.0 I!) Q '0 N q I I I I 8 . ‘ E 'I '\ E \z. I I ,5- I 1 1 1 1 1 1 1 ’ 9 m to N to AD V '0 N - O ( Iw/gfloux) wane/x 10:01 pun (lW/EOIX ) quwnN 10:01 (l/bw)uoq103 gogol no «5 v m N _ o f I I I I LL . '3 § '6 C O o O 9 O .1: U .‘L‘ o [—1 J I 9 05 co N (IW/g’ILOlX) amnion mm mm (IW/QOIX)1°QW0N MOI l970 I97l ISTO 25 Fluctuation in the ratio of carbon content to numbers or volumes are the result of fluctuations in the abundance of diatoms in relation to the other classes. Diatoms have a lower carbon content than do other species classes (Strathmann, 1967). Seasonal dynamics of the dominant algal classes, which differ in average volumes per species, also can help to explain seasonal shifts in mean individual phytoplankton volume (Figure 4). Similar seasonal dynamics of the mean individual volumes existed at all stations. They remained rather constant from spring to mid-summer, then increased sharply in late July. After peaking in August, corresponding with the blue—green bloom, the mean individual volume declined through the fall. Class dynamics: Successional patterns in class volume composition were generally the same at all stations (Figure 5). Diatoms, the spring dominants, were replaced first with increasing percentages of green algae then with larger percentages of blue-green algae until the blue-greens comprised over 90% of the phytOplanktonic standing crop in mid to late summer. During the fall the prOportions of blue- green algae decreased while diatoms increased. The summer replacement of diatoms and green algae by blue-green algae was most rapid in the discharge canal. The summer's green algal concentrations were most persistent in the river. Of the inshore stations, the discharge canal was most similar to the north and south lake stations while the river had the greatest similarity to the mid-lake station. Species dynamics: Twelve major phytoplankton species were observed during this study: five diatom species (Melosira granulata, Stephano- discus astreae, S. binderanus, S, niagarae, and Coscinodiscus radiatus), 26 Figure 4. Mean volume of phytoplankton organisms by station. north lake; - - - middle lake; —.-.- south lake; ----- discharge canal; ..... river. 27 . \. o. \. \ . x... .1 .. \o o II\I\ O\ \\ I\ \ '.\0\ \.\‘\ .00 I\ \\\ \ 00000000000 O\|“|“\ OOV‘AOQOO III-“I‘ll“ 0000000000 0A.! I I! 2......“ on“ I’ll! I” '1 .. ... ........ _. I.’ “Forums... ’ ~.\ m z u .. V . 3v ____________c_.x,~ 4. 2 0 8 6 4. 2 0 8 6 4. 2 0 8 6 4 2 3 3 3 2 2 2 2 2 I .l I ..l I 31.6.5 25...; .3232. :32 l970 Figure 5. 28 Mean seasonal variation in volumetric com— position of phytoplankton classes at the sampling stations during the study. Lower hatched area — blue—green algae; lower clear area - green algae; upper hatched area - diatoms; upper clear area - others. o o (D o 8 8‘ 8 8 b o 0‘ o N o 5 o 7 \‘ 7 l // l / 3.3. 30 five blue-green species (Anacystis cyanea, S, elachistra var. conferta, Anacystis sp., Aphanizomenon flos-aquae, and Oscillatoria sp.), and two green species (Coelastrum Sphaericum and Pediastrum duplex). These species all exhibited one of two basic volumetric dynamics patterns, irrespective of taxonomic class or stations: One pattern where the species' fluctuation between stations were generally similar with no obvious deviations and the other where the stations experienced dramatic unpre- dictable deviations with time (Figures 6-11). These erratic fluctuations were probably real, rather than sampling errors, because they occurred regularly in half the dominant species but were negligible in the remaining species. Sampling errors would, presumably, appear with about equal probability in each of the species. Therefore, some species appeared more constant in their ability to maintain their pOpulations. Melosira granulata was present at all stations on all dates during the study and was the dominant phytoplankton species during the spring (Figure 6). From spring dominance, their volumes generally decreased to a summer minimum in late August. The volume then increased erratically into the fall. Stephanodiscus astraea volumes varied strongly throughout the study period at all but the north lake station. In general, volumes were greatest in spring and fall and least during the summer (Figure 6). Erratic seasonal successional patterns also were observed for_S. binderanus (Figure 7). High spring volumes generally declined during the spring and summer with slight increases observed in the fall. Large spring volumes of S, niagarae disappeared completely from the lake by the end of May (Figure 7) and from the discharge canal by late June. A small pulse occurred at the river and mid-lake stations 31 Seasonal dynamics by volume of Melosia granulata and Stephanodiscus astraea at the sampling stations. - - - north lake; mid—lake; ---- south lake; -.-.- discharge canal; Figure 6. .... river. I- Stephonodiscus astraea 32 l ‘7- I 2 2 a c \\ I a ._——-" 5 --"""" ’fl .9 8 '1 .9 1 a 1 ' I6 2 9 9 "9 o (s 11 ) owmoA “goods ISTO l970 33 Seasonal dynamics by volume of Stephanodiscus binderanus and S, niagarae at the sampling stations. - — - north lake; mid-lake; ---- south lake; —.—.- discharge canal; .. river. Figure 7. 34 IO” ogoroe SCUS m SCUS hm Stephanod: 0d! 1. _ deforms Stephan w—fi __\. “ “....‘ _~_ “ I :1. oEEo> u0._uoum 3 m. 10’ 1970 1970 35 in conjunction with the summer blue—green bloom. The abundance of_S. niagarae generally increased during the late summer and fall in the lake and discharge canal, but was absent from the river after the mid-summer pulse. Of the major species observed, the diatom Coscinodiscus radiatus displayed the least spatial and temporal variability (Figure 8). Spring volumes gradually increased to the maximum observed volumes in late summer and fall. Anacystis cyanea was absent from the spring samples but increased rapidly during the summer and established phytOplanktonic dominance of the summer blue-green bloom (Figure 8). Their populations then declined moderately during the fall. Although temporal variation in the volume of this species was great, the changes were spatially uniform. .5. elachistra var. conferta was abundant at one or more stations during the whole study but contributed to the total abundance at all stations most consistently during the summer blue-green bloom (Figure 9). Their abundance sharply declined in the lake during the fall while it remained relatively but unpredictably high at the inshore sites. Anacystis incerta attained greatest abundance in June before the other abundant blue-green algae. But they also contributed greatly to the mid-August bloom (Figure 9). The population volumes also changed erratically with little uniformity among stations. Both species of abundant filamentous blue-green algae, Aphanizomenon flos-aquae and Oscillatoria sp., exhibited similar seasonal dynamics (Figure 10). Maximum abundance was observed in late summer and early fall at all stations except the discharge canal where the seasonal maximum was reached in late June. 36 Figure 8. Seasonal dynamics by volume of Coscinodiscus radiatus_and Anacystis cyanea at the sampling stations. - - - north lake; ' mid-lake; —--- south lake; -.-.- discharge canal; . . . . river. 37 .0. no. .L 00— l 1 so. 00:96 23392 3.068 3360583 0. l l o (t d) amnloA sauaads Figure 9. 38 Seasonal dynamics by volume of Anacystis elachistra var. conferta and S, incerta at the sampling stations. - - — - north lake; mid-lake; ---- south lake; -.-.- dis— charge canal; ..... river. Anacystis incerta IO' Anacystis elachistra var. conferta 107 39 0.. ...."lo ..... ..oo ’—" no“ 05 l |O 1 | (s ) OwnIoA “mods 1970 1970 Figure 10. 40 Seasonal dynamics by volume of Sphanizomenon flos—aguae and Oscillatoria sp. at the sampling stations. - - - - north lake; mid-lake; —-—- south lake; -.-.- discharge canal; ..... river. 41 .8 0:22:30 L 3:8 -3: 3563222 0. no. to. no. no. so. no. (‘1!) amnloA saiaads 42 The two major green phytoplankton species found were quite diff- erent in their seasonal distribution (Figure 11). Pediastrum duplex in- creased from low spring volumes to maximum in late June, then uniformily decreased little during the rest of the study period. Spring and early summer volumes of Coelastrum_§phaericum completely disappeared during the August blue-green bloom, but reappeared to nearly their pre-bloom abundance afterwards. Of the minor species, three deserve special mention. Cyclotella meneghiniana commonly occurred in the river where it comprised up to 5.8% of the phytoplankton volume. While it was frequently found at other stations, its role was much less important. Botryococcus sudeticus occurred commonly in the spring samples when it accounted for up to 17% of the phytOplanktonic volume of the - lake. Its abundance then decreased to a rare and unimportant occurrence. Euglena Sp. occurred frequently throughout the study area during this investigation, but with one exception, it accounted for less than 1% of the total phytOplankton volume. It comprised about 10% of the volume in the discharge canal during the spring. Phytoplankton Diversity and Equitability Nearly 200 different species of phytoplankton were observed during this study. Of these species 94 were diatoms, 23 were blue-green algae, 79 were green algae, and the remaining few were from the EuglenOphyceae, Dinophyceae, and ChrySOphyceae (Table 3). Not all species were found at all stations, but there was nearly (> 95%) com- plete overlap between the species found at the lake stations and the species observed at the inshore stations over the study period. A slightly greater number of species was found in the discharge canal Figure 11. 43 Seasonal dynamics by volume of Coelastrum Sphaericus and Pediastrum duplex at the sampling stations. - — — - north lake; mid-lake; -—-- south lake; -.—.- discharge canal; .... river. q 2 4—4 0 d U) —1 ¢ 3 p O E 3 3 t: a d E _ a L l I I fia—J q 2 I -“——-'--’-: .\ / ---’-——--— 03....... . ---—-“-—- .0..0"°.... O E 3 U 'C O O ‘é E 3 L ‘ U! 2 3’ l l l l l n ‘-v "" "' ‘o B i: <2 2 s 9 9 71 (s ) awnloA sauoads I970 l970 C. heticuiatum (Dang.) Senn 18. Table 3. Species found during study listed by class with corres— ponding mean annual species volumes (U3). CLASS MEAN VOLUME Specieb CYANOPHYCEAE A. quadupflicaium (Menegh.) Bréb. 42 Anabaena ukn 1 2,640 Anabaena ukn 2 631 Anacystis cyanca (Kfitz.) Dr. & Daily 81,991 A. mama w. & G. S. West var.c0n6€./Lta W. & G. S. West 37,692 A. gneviflfiei (Berk.) Kfitz. 201,552 A. incenia (Lemm.) Dr. & Daily 106,447 A. Zimnetica (Lemm.) Dr. & Daily 967 A. minuta (Ag.) Menegh. 535 A. putahaa Gardn. 8,181 A. thenmazla (Menegh. ) Dr. & Daily 165 Aphanizomenon 6306- aquac (L. ) Ralfs 4,936 COCCOChKOALA ukn 1 15,339 C.-nidu£an6 (Richt.) Dr. & Daily 1,527 C. peniocyéw (Kiitz.) Dr. 5. Daily 151 C. nupcatnia (Lyngh.) Spreng. 418 G. tacuaznia Chodat 268 G. naegezianum (Ung.) Lemm. 3,882 memw 6829mm A. Braun 25 OaciftaZOALa sp. 4,139 Spituflina ZaxLAALma G. S. West 126 unknown blue green colony 836 unknown blue green unicellular 78 CHLOROPHYCEAE Acténwsvuun mac/(366mm a. M. Smith 1,405 A. hanIZAchii Lagerheim 131 A. hantzachii Lagerheim var. fifluuiatifie Schroeder 248 Anhibtnodebmub conuotutua Cords 14 A. 6a£ca£u6 (Cords) Ralfs 38 Botnyococcub btaunii Kfietzing 3,882 B. Audeticub Lemmermann 14,137 Camellia 2.6666501;an Cerneck 421 C. uutganib Beyerinck 579 CZOAZetium sp. 194 Coeiaaznum mLCAOpOnum Naegel 4,808 092 46 Table 3 (con't.) CLASS MEAN VOLUME Speciea CHLOROPHYCEAE (con't.) C. Sphaenicum Naegeli 31,059 Coe£a6tnum sp. 28,736 COAmanium bipunctatum Boergesen 20,897 Coamatium Sp. 1,151 Cnucigcnta attainani G. M. Smith 219 C. apicutata (Lemm.) Schmidle var. ehienbib Tiffany & Ahlstrom 1,764 C. fieneatnaia Schmidle 302 C. Lnaegutania Wille 114 C. Kautcnbonnei Schmidle 1,005 C. quadnata Morren 103 C. tetaapedta (Kirch.) w. a G. S. West 198 DactyfiocOcCOpALA Smithii R. & F. Chodat 491 DictyOAphaenium ehhenbengianum Naegeli 171 D. pflanctonicum Tiffany & Ahlstrom 3,195 Gtoeocyatia ueaicuioaa Naegeli 905 Gotenhtnia nadiara (Chod.) Wille 408 Kétchnetietta contotta (Schmidle) Bohlin 229 K. Zunaflib (Kirch.) Moebius 54 K. Obeaa (W. West) Schmidle 94 K. Aubiotizanta G. S. West 8 Kitchnetietfa sp. 96 Lagenheima quadniaeta (Lemm.) C. M. Smith 46 Micnactinium calenae Tiffany & Ahlstrom 1,928 M. pubiiflium Fresenius 7,238 Micnactinium sp. 2,185 Mougeotia sp. 6,222 Oocybtib bongei Snow 225 Oocybtib Sp. 199 Pandonina monum (Mue11.) Bory . 619 Pediaatnum binadiazum Meyen 31,161 P. bonganum (Turp.) Meneghini 5,089 P. dupflex Meyen 14,675 P. Aimptex (Meyen) Lemmermann 14,907 P. tctnaa (Ehr.) Ralfs 1,854 PtanRIOAphaenia getatinoaa G. M. Smith 1,317 Pfleodonina sp. 15,708 PotycanOpALA quadnLApina G. M. Smith 227 Quadaigufa ctoatenloideé (Bohlin) Printz 156 Q, Kacuainia (Choda) G. M. Smith 26 47 Table 3 (con't.) CLASS MEAN VOLUME Specieb CHLOROPHYCEAE (eon't.) Scenedebmub abundanA (Kirch.) Chodat 34 Scenedebmub acuminatub (Lagerh.) Chodat 248 S. bennandii G. M. Smith 75 S. bijuga (Turp.) Lagerheim 81 S. denxicufiaiuA Lagerheim 118 S. dimonphué (Turp.) Kuetzing 176 3. OpofiienAiA P. Richter 91 S. quadnicauda (Turp.) de Brébisson 106 S. quadnicauda (Turp.) de Brébisson var. a£tetnan6 G. M. Smith 21 Schnoedenia Aeiigcna (Schroeder) Lemmermann 61 Seflenabtnum bibhaianum Reinsch 490 S. gnacifie Reinsch 202 S. minuium (Naeg.) Collins 31 S. we6tii G. M. Smith 49 SphaQ/Locgbw Adi/108mm Chodat 2,036 Stauiaétnum sp. 10,761 Tetaaednon anthnonAmifionme (G. S. West) Woloszynska 226- T. caudaium (Corda) Hansgirg 16 T. pentaaednicum w. & G. S. West 14 T. Inigonum (Naeg.) Hansgirg 48 T. thigonum (Naeg.) Hansgirg var. gaaeific (Reinsch) De Toni 26 Tainabpona sp. 57 Teifiabtnum aficganb Playfair 75 T. gflabhum (Roll) Ahlstrom & Tiffany 155 T. hetehacanthum (Nordst.) Chodat 75 T. Atauhogeniacfianme (Schroeder) Lemmermann 75 unknown green colony 920 unknown green unicellular ' 123 WQAIQKZa bothyoideb (W. West) de Wildemann 690 w. Kineaflié G. M. Smith 1,216 BACILLARIOPHYCEAE Achnantheb {anceofiata Bréb. 403 A. Minuiibbima Kfitzing 119 Amphona OUQKLA Kfitz var. peducufiub Kfitzing 340 A6£enione££a 60nm06a Hassall 523 48 Table 3 (con't.) CLASS MEAN VOLUME Specieb BACILLARIOPHYCEAE (con't.) Centric ukn l (Cgcfioteflfia gfiomeaata Bachmann?) 36 Centric ukn 2 108 Centric ukn 3 122 CocconeiA diminuta Pant. 25 C. dibcufiué Schum. 220 C. pflacenzufia Ehrenberg 114 Cabcinodiécué nadiazub Ehrenberg 3,618 Cycfiotefifia bodanica Eulenst. 832 C. butzingiana Thwaites 445 C. meneghiniana Kfitz. 850 C. ocefiflata Pant. 241 C. Atefifiigeha Grun. 71 Cymatopfleuha 6022a (Breb.) w. Smith 3,430 Cgmbeflfia againié Kfitz. 1,006 C. venzhLCOAa Kfitz. 121 Cgmbefiia sp. 49 Diatoma tenue Ag. 978 D. qugane Bory 9,542 Epitheméa Acnex Kfitz. 3,225 E. tungida (Ehr.) Kfitz. 4,953 Eunotia cuhuata (Kfitz.) Lagerst. 1,133 E. pantinaflib (Kfitz.) Rabenhorst 1,125 Fnagiflaaia bnevibtfliaia Grun. 664 F. capacina Desmaziéres 361 F. conbtnucnb (Ehr.) Grunow 1,866 F. anotoncnbiA Kitton 6,524 F. £2pt06taunon (Ehr.) Hustedt 11,699 F. pinnata Ehrenberg 1,584 Fhagiflamia sp. 3,783 Gomphonema conAtnictum Ehrenberg 1,844 G. ofliuaceum (Lynghye) Kfitz. ' 657 G. panvufium Kfitz. 353 G. 6a4c0phagu6 3,326 GgMOALQma Apencahii (w. Smith) Cleve. 5,734 HaHIZAchia amphéoxga (Ehr.) Grun. 2,011 M2808Lna ambigua (Grun.) o. Mfiller 1,317 M. dibtané (Ehr.) Kfitz. 2,413 M. gnanufiata (Ehr.) Ralfs 6,828 M. LAfiandica 0. Mfiller 3,802 Menidion cLhcuZaie Agardh 2,127 Nauicufia bacififium Cleve. 3,461 N. contenza Grun. 1,084 49 Table 3 (con't.) CLASS MEAN VOLUME Specieb BACILLARIOPHYCEAE (con't.) N. Chyptocephafia Kfitz. 601 N. 006p£data Kfitz. 10,912 N. exigua (Gregory) 0. Mfiller 703 AL gabtfium Ehr. 2,690 N. hungaaica Grun. 300 N. mutica Kfitz. 1,226 N. pupufla Kfitz. 950 N. AaCLnanum Grunow 594 N. Imipanctata (0. F. Mull.) Bory 2,376 N. vinidu£a Kfitz. 7,046 N. ukn 1 122 N. ukn 2 499 N. ukn 3 9,236 Neidium dubium (Ehr.) Cleve. 8,847 NLIZAQhLa acicuflanfa W. Smith 384 N. amphibia Grunow 245 N. angubtata (W. Smith) Grunow 3,915 N. diébipata Grunow 1,004 N. fiiiifionmib (W. Smith) Hustedt 691 N. gnaciiib Hantzsch 628 N. hoflbatica Hustedt 112 N. flineanié w. Smith 3,968 N. paflea (Kfitz.) W. Smith 495 N. Aigma (Kfitz.) w. Smith 1,307 N. 6igmoidea (Ehr.) w. Smith 16,632 N. ukn 1 577 Up phona mattgi Herib. 2,733 Pennate ukn 1 1,232 Pennate ukn 2 85 Pinnufiania boncafiib Ehrenberg 1,730 P. Uénidib (Nitzsch.) Ehrenberg 6,172 Pinnuflania sp. 301 Rhizo¢o£enia etienALA H. L. Smith 9,842 RhOLCOAphCnLa cuhuata (Kfitz.) Grun. 119 Stephanodibcub azpinub Hustedt 2,215 3. a614aea (Ehr.) Grun. 3,095 3. bindenanué (Kfitz.) C. Weber 10,616 3. niaganae Ehr. 16,409 3. tenuii Hustedt 429 S. ukn 1 381 SutLheZfia anguAta Kfitz. 1,570 3. avata Kfitz. 1,102 50 Table 3 (con't.) CLASS MEAN VOLUME Specieé BAC ILLARIOPHYCEAE (con' t. ) Synedha acué Kfitz. 2,062 S. nana Meister 115 S. puha8£iica W. Smith 220 S. uflna (Nitzch.) Ehr. 4,109 Tabefiflaaia fienebtnata (Lyngbye) Kfitz. 1,860 T. fifloccu£OAa (Roth) Kfitz. 1,857 EUGLENOPHYCEAE Eugfiena sp. 2,171 Thacheflomonab Sp. 532 DINOPHYCEAE Cenaiium hihundineflfia (0. F. Mfiell.) Dujardin 10,173 Fenian/(um sp. 6,234 CHRYSOPHYCEAE Dinobhgon sp. 3,013 51 (147) than in the river (125) or at the three lake stations (from north to south: 121; 123; 116). During the sampling period the most kinds of species consistently were found in the inshore areas, particularly the discharge canal. The number of species erratically increased from spring to fall throughout the study area (Table 4). All stations in the spring had nearly the same number of species. Over the summer the greatest number of species were found at the inshore stations. In the fall the lake stations had approximately the same number of species as the river while the dis- charge canal continued to have greater numbers. Table 4. Number of species found on each date and the annual means by station. Date Stations 1 3 6 8 9 2 May 1970 43 47 46 49 36 28 May 1970 53 53 54 54 57 23 June 1970 54 58 48 72 64 21 July 1970 50 62 31 7O 66 23 August 1970 64 50 53 58 63 15 September 1970 41 48 38 65 62 10 October 1970 66 '60 62 82 67 7 November 1970 56 66 58 72 57 Annual Means 53.4 56.6 48.8 65.3 59. 52 Mean species diversity calculated by station from numbers of phytoplankton differed significantly (p < 0.05) among stations on all of the dates sampled (Appendix, Table A7). As with the numbers of kinds of species that were observed (Table 4), the inshore stations tended to have greater diversities than those for the lake stations. Diversi— ties in the discharge canal ranked greatest 87.5% of the time. The river ranked in the highest category on 75% of the dates. The lake stations varied inconsistantly among themselves. Discernable differences (p < 0.05) in equitability (calculated with numbers of phytoplankton) were also detected among stations on each date (Appendix, Table A8). Only the river station demonstrated anything that approached a consistant rank among stations. On 62.5% of the observations, the river fell into the smallest equitability category. The remaining stations varied inconsistantly. Apparently, the relatively high diversities found in the inshore areas originated from the greater number of species per unit volume rather than from greater equitability of species abundances. Seasonal averages in diversity and equitability further emphasize the greater diversity of the inshore areas over the lake stations while the equitabilities among the five stations remained quite similar (Table 5). Diversity and equitability estimates were also calculated on volumetric measurements. Although volumetric calculations of diversity and equitability differed from numerical calculations in absolute value, the relative values among stations were similar. The seasonal dynamics of diversity and equitability by station over the period of investigation are summarized in Figure 12. These estimates of values for the north and middle lake stations were low in 53 Figure 12. Mean diversity and equitability of phytoplank- ton by station on each sampling date. Upper hatched boxes - diversity; lower clear boxes - equitability. O50. >62 1. to 0. 36m 9 2.4 mm 32. .m 25.. mm .82 mm .62 u mtg—:35 m.n1.¢m. mo. fin. mo. v.0 m_o. .36.. mo. ....» m_o J.» mo .6.» mo. mm. mo. _ _ r _,_ §§\§§§\N\\\s§ $8 .1 .1 _ _.l % $6 \\\\\\ \\\\\\\ \\\\\\\\ \\\\\\k \\\\\\. \\\\\\\\ . . _§\\\\\\. § y 137 $8 m. $8 808.88 8. SSNSW § -. _ H ..IIWNI. .. $0 S\S\\\\\\\ S.s\\\_\\\\\ NM _ _ 0.0 05.0 0.. 05..0 0.. 05.0 0.. 05.0 0.. 0.5.0 0.. 05..0 0.. 05.0 0.. 05.0 0.. 3.23.0 “OHDTS 55 Table 5. Mean diversities and equitabilities at the sampling stations during the study period. Station Numerical Diversity Numerical Equitability 1 3.44 0.313 3 3.73 0.344 6 3.53 0.373 8 4.09 0.360 9 4.06 0.390 the spring, increased until the late summer when it decreased and then gradually increased in the fall. Values for the south lake station were somewhat higher in early May than found at the other lake stations; they dropped in late May, increased in June, and then followed the general pattern that occurred in the rest of the lake. Inshore stations had fairly constant diversities and equitabilities throughout the sampling period. Community Metabolism Mean midday gross primary productivity was most consistently great- est in the discharge canal (Figure 13). Productivity in the discharge canal was exceeded on only one occasion at the lake station. This occurred during the summer blue-green algae bloom when midday productivity in the lake reached 412.5 mgC/mz/hr. Maximum productivity in the discharge canal was observed a week later (350 mgC/mZ/hr). The primary productivity in the river never exceeded that of the canal, but it significantly (: 28E) exceeded productivity in the lake 56 Figure 13. Mean gross primary productivity (i i 1 SE) estimated during midday incubation periods. lake; -.—.- discharge canal; .... river. 050. 80 Row 2.4 :3. 2.2. has. .82. 8.2. 82. 8a.. 89. 8o. . __~__ _ _ q . d _ u _ _ q q q _ fi/ .5. PJ O0 00 om ON. O0. 00. O .N OVN O5N 000 000 000 000 ON¢ (Jq kin/30w) Mgnuonpmd $3019 58 during the summer on one occasion. For most sampling dates mean river productivity was lower than lake productivity. Primary productivity in the lake generally increased from spring to late summer when it peaked strongly during the August blue—green algae— bloom. After the bloom the lake productivity returned to the relatively stable pre—bloom summer level. Profiles of average gross primary productivity for the three stations over the study period show that the highest rates of production occurred at the surface level in each case (Figure 14). Rates of decline from the surface to 0.5 m were similar at all three stations with lower rates of decline existing from 0.5 to 1.5 m. Little change was exPerienced where there was low to negligible productivity from 1.5 to 2.5 m at the stations. Hence, the majority of the primary productivity in the study area was observed to occur in the t0p 1.5 m of the water column. Estimates of diurnal primary productivity were made on 1 July 1970 for the lake (station 3) and discharge canal (station 8). Maximum pro- ductivity was observed to occur during early afternoon (Figure 15). At this time the discharge canal was found to produce 3730 mgC/mzlday while the lake produced 1935 mgC/mz/day. Mean community respiration estimated during the productivity incubations are listed in Table 6. On two occasions oxygen increased in the dark bottles resulting in positive respiration values. These samples, 23 June 1970 in the discharge canal and 1 September 1970 in the lake, are omitted from the table. Community respiration was nearly always lowest in the lake. The greatest community respiration measured in the lake (288 mgC/mZ/hr) corresponded with the blue-green algae bloom. 59 Figure 14. Profiles of average gross primary productivity over the study period. lake; .... discharge canal; —.—.— river. 60 01 0.5 4 1.0‘ 1.53 Depth (m) 2.0‘ ' 2.5- T 0 0.03 0T06 0.89 0.12 0.15 0.18 0.21 0.24 0.27 Primary Productivity (mgC/ liter/hr) Figure 15. 61 Diurnal primary productivity in the lake and discharge canal on 1 July 1970. 62 ....u T9: n o TV 0" O ' S ...-D C .u L r3 - I M M .n r9 :7 +1.... oi ... . ... cs 5 7 cl 5 8 2 6 tr.\«E\UmE. 3.2.2.09...— $0.0 Hours Discharge Canal Station :5 m. o 0 374- 312- 2504 187‘ 125‘ .E\«E\UmE. >..>_.u:fiok_ $0.0 Hours 63 Table 6. Mean community respiration (mgC/mZ/hr) estimated during productivity incubation at the sampling stations (x i 1 SE). DATE LAKE DISCHARGE CANAL RIVER 5-1 - 307 i 17 5—15 116 i 27 116 i 33 293 i 12 5—27 75 i 0 590 i 28 674 i 13 6—10 122 t 34 477 i 91 321 i 16 6—23 75 i 8 131 i 15 7—7 47 i 8 110 i 6 214 i 33 7-21 69 i 4 260 i 31 279 i 21 8-4 107 i 6 345 i 55 190 i 7 8—24 288 i 59 218 i 11 185 i 21 9—1 - 360 i 11 211 t 1 9-29 23 i 12 12 i 6 88 i 28 10-27 - 1259 i 19 198 i 0 64 Maximum respiration at both inshore areas (excluding the aberrant fall discharge canal value resulting from possible instrument error) was recorded on 27 May 1970. At that time communities in the discharge canal consumed 540 mgC/mz/hr, while the river community consumed 674 mgC/mz/hr. During the spring the river respiration exceeded the respiration in the discharge canal. Similar community reSpiration occurred at both inshore areas during the first part of the summer. Respiration in the discharge canal tended to exceed respiration in the river for the remainder of the study period. DISCUSSION Diurnal Productivities and Community Respiration Midday estimates of primary productivity do not allow for the influence of the length of day on overall daily productivity. In order to compare primary productivity estimates with previous work, the daily productivity was estimated for each sampling date at the three stations sampled based on the diurnal estimates of 1 July 1970. As- suming that the shape of diurnal productivity curves and the time of peak production remained constant, daily productivities were calcu- lated by constructing curves around the time of peak productivity observed on all sampling dates and the corresponding times of dawn and dusk. Calculations based on the areas under the curves were used to represent the diurnal productivities. Mean daily and seasonal productivities by station are listed by season in Table 7. The daily values found are comparable to the lower limits of the range of primary productivity values summarized in Saunders' (1964) review of values for the western basin of Lake Erie. The values estimated were indicative of eutrOphic conditions defined by Rodhe (1969) as resulting from man induced nutrient enrichment. Total respiration on a daily basis was calculated by simply multiplying by 24 the mean hourly respiration observed during the pro- ductivity estimates at the stations. Similar day to night community respiration rates were found by Verduin (1957) in Lake Erie. The daily respiration values were used to calculate the ratios of mean daily 65 66 Table 7. Estimated mean seasonal gross primary productivity of the phytOplankton at the sampling stations. Lake Canal River Spring gCImZIday 0.9 (4)1 2.0 (4) 0.8 (5) gC/mzlseason 78.3 185.8 71.0 Summer gC/mzlday 1.7 (6) 2.7 (6) 1.5 (5) gC/mzlseason 159.2 250.7 141.2 Pall 8C/m2/day 0.7 (1) 2.2 (2) 0.7 (2) gC/mfl/season 62.9 100.1 63.7 Total gc/m2/274 days 300.4 (11) 536.5 (12) 275.9 (12) 1Designates number of sampling dates 67 phytOplanktonic gross primary productivity to community respiration (P/R) at the sampling stations. Examination of these ratios in Table 8 show that the study area, except on rare occasions, is hetero- trophic. The river particularly consumed more than was produced. Most of the respiration is probably contributed by organisms other than the phytoplankton, primarily bacteria. This is most obvious in the river. For example, on 27 May 1970, when the highest respiration was observed in the river, the highest coliform bacteria population occurred in the river (Cole, 1972) while phytOplankton abundances were among the smallest observed. The consistently low P/R ratios in the study area emphasize the importance of detritus in the system. During this study the average contribution of the phytOplankton to the total particulate organic carbon (Cole, 1972) was minor: 4.8% in the river, 15.2% in the discharge canal, and 27.5% in the lake. The zooplankton contributed much less than the phytOplankton. ZOOpIankton were rarely observed during phyto— planktonic enumeration. Steele (1969) noted that the role of detritus in aquatic communities may be as important as plankton. It appears that this is particularly true for the near shore areas of western Lake Erie, with the detritus perhaps being more important than the plankton in community energetics. Regulation of AbundanCe and Productivity PhytOplankton productivity has been observed to be regulated by a combination of physical, chemical, and biological environmental factors (Hutchinson, 1967). Primary among the physical parameters are temperature, light, and turbulence. Chemical regulators include nutrient levels and the influence of toxic materials. Competition for 68 Table 8. Ratios of mean daily phytOplanktonic gross primary productivity to community respiration (P/R) at the sampling stations. Date Lake Discharge Canal River 5-1 -- -- 0.06 5—15 0.26 0.36 0.09 5-27 0.25 0.14 0.02 6-10 0.44 0.21 0.25 6-23 0.55 -— 0.18 747 0.96 1.21 0.36 7-21 0.54 0.35 0.45 8-4 0.59 0.26 0.11 8-24 0.57 0.42 0.35 9-1 -- 0.34 0.15 9-29 1.23 4.54 0.18 10-27 -- 0.03 0.07 Mean 0.60 0.79 0.19 69 nutrients and light plus grazing pressure rank as major biological controls. Low water temperatures appeared to be a major cause of diatom dominance in the spring and a contributing factor to their increase in the fall. Slightly higher temperatures in the discharge canal, combined with slightly lower light penetration and depressed nitrogen concentra— tions, also may have contributed to the relatively early occurrence of blue-green algal dominance in the discharge canal. For most of the study period, however, temperatures were quite uniform throughout the study area. Consequently, they could not have been responsible for differences incurred in phytOplanktonic productivity throughout the area. The role of light appeared to have great importance in the phyto? planktonic regulation in the study area. Daily primary productivity observed in the discharge canal closely followed the photoperiod. Maximum daily primary productivity in the discharge canal was observed about two weeks after the summer solstice. This lag of two weeks may have resulted from the modifying effects of temperature and nutrient concentrations. Thereafter, the primary production in the discharge canal gradually declined for the remainder of the study, except for a second significant peak in September. The river and lake exhibited no obvious relationship to photoperiod, except in possible combination with temperature to reduce early spring and fall algal productivities. Light penetration was severely limited at all stations, limiting most algal productivity to the upper meter. Below 1.0 m, low light availability appeared to limit photosynthetic activity. The depth of light penetration in the lake appeared to be related to wind induced turbulence. During periods of relative calm when diurnal stratification 70 was observed to develOp in the lake (Cole, 1972), settling of suspended particular matter could occur. This permitted increases in the illumina- tion at the lower levels and possibly allowed increases in the primary productivity at the lower levels. Such was the case observed on 1 July 1970, during late morning to mid-afternoon, similar productivities were observed throughout the evaluated water column in the lake. Also on 4 August 1970, during a period of relative calm, the productivities at 0.5 and 1.5 m were observed to generally exceed the values for these levels during more turbulent periods. Surface values did not, however, reflect the calm conditions nor were there obvious differences in the productivity profiles of the inshore areas, indicating that factors other than light were limiting these pOpulations. Wind induced turbulence in the lake, in addition to increasing turbidity and causing vertical homogeneity of the phytoplankton, appeared to cause a general reduction in the photosynthetic potential of the lake's phytoplankton. Examination of the various physical and chemical parameters analyzed concurrently with this study (Cole, 1972) Show that wind-induced severe wave action in the lake had a sufficiently (zonsistent difference from the discharge canal to account for the reduc- 'tion in the photosynthetic capabilities of the lake from that of the (iischarge canal. The heavy wave action often experienced by the lake CHDuld have caused a disorientation in the lake's plankton that resulted 111 decreases in their reproductive and photosynthetic abilities. Allen (1920) felt that a similar disorientation caused population reductions 111 lake plankton discharged into a lotic system. This persistant reduc— thlon in production capabilities may partially explain why surface primary iPfltoductivities in the lake did not significantly increase, as did lower 14avels of the water column, during periods of relative calm. 71 Low river primary productivities and phytOplankton abundances may be associated with some unidentified toxic inhibition. Nalepa (1972) felt that adverse environmental conditions, particularly low oxygen concentrations, in conjunction with river discharge were the primary regulators of zooplankton in the river at the time of this study. River velocities do not appear to influence negatively the phytoplankton volumes and primary productivities, because some of the highest phyto- plankton populations occur in the river at the time of greatest river discharges in the spring. Changes in the productivity and biomass are not related to changes in oxygen concentration in the river. Nutrient levels are greatest in the river and temperature and light do not differ greatly from the other areas. By deduction toxic inhibitors are most. likely limiting river productivity and biomass. Carbon, of the three nutrients (carbon, phosphorus, and nitrogen) that are most frequently associated with limiting algal production (Hutchinson, 1967), appeared least likely to occur in quantities suffic- iently low to limit productivities. Alkalinities in the area range around 100 mg/liter (Beeton, 1963). This is reflected in the generally high dissolved organic carbon concentrations (3—6 mg/liter) observed throughout the study at all stations (Cole, 1972). Phosphorus concentrations during most of the study do not appear to limit the phytOplanktonic activity in the study area. At no time does the phosphorus concentration fall below a level observed by Sawyer (1947) to possibly limit algal activity. However, total and dissolved phosphorus concentrations were observed to increase in conjunction with the late summer blue-green algae blooms in the study area. This implies that, while phosphorus alone is not limiting, its presence in extremely 72 high concentrations enabled the blue-green algae to Optimize existing environmental conditions that permitted a bloom. Nitrogen concentrations appear to be a major factor controlling algal succession and composition in the river, lake, and, to a lesser extent, the discharge canal. Nitrate—nitrogen appears to be cloSely related to blue-green algal succession in the study area. The decline of nitrate in July to below 0.3 mg/liter, the often cited level of poss- ible inorganic nitrogen limitation (Sawyer, 1947), coexisted with the dominance (95%) of blue-green algae in the lake. In the river the ni- trate concentration remained greater than 0.3 mg/liter into August. There the blue-green dominance was not encountered until August. Blue- green algae are capable of optimizing low nitrogen concentrations only in situations where phosphorus is not limiting, and higher phosphorus concentrations yield higher blue-green algae productivities (Ogawa and Carr, 1969). This accounts partially for the late summer blue-green blooms which occurred in conjunction with a phosphorus pulse in the study area. Some of the major Species observed during the bloom were regarded as nitrogen fixers by Ogawa and Carr (1969). Howard, §£_al, (1970) observed nitrogen fixation to occur in Lake Erie during the summer. The relatively early dominance of blue-green algae in the discharge canal was possibly caused by an early depression in nitrate concentra— tions combined with slightly lower light penetrations, associated with high suspended solids concentrations (Cole, 1972), and slightly higher water temperatures. The possible role of zooplankton as a regulator of phytoplankton abundances is suggested by seasonal changes in phytoplankton, 200plank- ton, and particulate carbon. The volume and carbon content of the algae did not parallel productivity in the study area. Productivity per unit 73 volume in the discharge canal was lowest for most of the spring and fall, and highest in the summer. The river in contrast had the lowest ratios in late summer. In the lake the highest productivity per unit volume occurred in mid-summer shortly before the August blue-green bloom. Productivities in the lake and discharge canal remained relatively constant during the summer until the bloom, while community respiration and algal volume declined slightly. Productivity was not being stored as detrital carbon in the water because total organic carbon con- centrations did not increase during this period (Cole, 1972). Since little net movement of carbon to the sediment is expected in the turbulent lake, much of the produced carbon may have moved to consumers. Nalepa (1972) showed that increases in the biomass of zOOplankton were greatest at that time. Z00p1ankton consumption may have depressed the volume of phytOplankton at a time when the zooplankton were most abun- dant in the lake and discharge canal, while gross primary productivity was maintained. Z00plankton grazing also may have influenced changes in the mean size of the algae, which increased during the summer as zooplankton abundances increased. The bloom occurred when zooplankton abundance was greatest and indicates that zooplankton did not limit productivity at that time, although they may have influenced algal species composition so that large blue-green algae were favored. Community-Structure EutrOphication, it has been hypothesized, results in increased sizes of organisms (Hall, gt fl1°a 1970) and decreased diversities (Wilhm and Dorris, 1968). The results of this study do not suggest such a simple and direct relationship. The river appears to be the most enriched but productivities are relatively low and diversity relatively high. 74 Unidentified toxins may be responsible for low productivities, but if so they seem to affect all species equally rather than affecting some species at the eXpense of other species. Diversities and productivities were both observed to be highest in the discharge canal. Williams' (1964) work has implied that diversity varied indirectly with produc- tivity but that relationship does not appear to hold in this study area. Diversity differences in this study area appear to be caused pri- marily by differences in the concentration of rare species; equitability was much less a factor. Rare species, possibly derived from surrounding marsh areas occurred more frequently in the river and discharge canal. It is possible that reproduction of the rare species was limited in the lake and they were diluted out or died by the time they reached the lake stations. The phytoplankton pOpulations of western Lake Erie exhibit exten— sive quantitative and qualitative changes from year to year. This stimulated Chandler and Weeks (1945) to write, "General statements concerning phytOplanktonic production in these waters (western Lake Erie) based on observations limited to a season or even a complete year might be very misleading." Part of this variability can be explained in that a body of water the size of western Lake Erie is capable of containing very different populations of phytOplankton at the same time. This was observed by Verduin (1952) in the island region. Studies are continuing to determine annual phytOplanktonic variability in the near-shore areas of Lake Erie, as related to possible regulatory factors. In order to achieve a reasonable level of certainty concerning possible nutrient limitation in the study area analyses such as in EIEE. nutrient enrichment bioassays should be performed. These results could 75 then be applied to the field observations to aid in determining the impact of the various parameters. The only other comprehensive study of the total phytoplankton populations of the River Raisin area of Lake Erie was conducted by Wright and associates (1955) in 1929 and 1930. This early study had only one station in the area "about two miles out form the shore". 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PhytOplankton density (no./ml) arranged in order of increasing abundance at the sampling stations. 2 May¥1970 28 Station Mean Multiple Range Mayrl970 23 Station Mean Multiple Range June 1970 21 Station Mean Multiple Range Ju1y71970 23 Station Mean Multiple Range August 1970 15 Station Mean Multiple Range September 1970 Station Mean Multiple Range 6 3 8 9 1 678 1381 1482 3277 6478 9 3 l 6 8 1259 2101 2530 2530 6065 9 6 3 1 8 1196 1329 1715 2507 6333 6 1 3 8 9 157 265 512 1156 1289 9 1 8 3 6 949 1132 1606 2145 2267 3 6 8 1 9 450 535 673 1091 1509 Table A1 (con't.) 10 October 1970 Station Mean Multiple Range 7 November 1970 Station Mean Multiple Range 667 395 82 1126 434 8 1 9 1598 1621 1865 3 9 8 1224 1320 2191 83 4 Table A2, Phytoplankton volume ( x 10 .03/m1) arranged in order of increasing abundance at the sampling stations. 2 May 1970 Station 6 8 9 3 1 Mean 392 614 656 859 3956 Multiple Range 28 May 1970 Station 9 3 1 6 8 Mean 275 785 1204 1486 2928 Multiple Range 23 June 1970 Station 9 6 3 l . 8 Mean 269 700 889 1538 3979 Multiple Range 21 July 1970 Station 6 l 3 9 8 Mean 56 148 242 269 917 Multiple Range 23 August 1970 Station 9 1 8 3 6 Mean 2084 2412 2555 7026 7382 Multiple Range 15 September 1970 Station 3 8 6 9 1 Mean 553 792 941 1004 1804 Multiple Range Table A2 (con't.) 10 October 1970 Station Mean Multiple Range 7 November 1970 Station Mean Multiple Range 84 6 9 3 8 1 404 628 983 1196 1367 1 6 9 3 8 228 238 291 864 975 85 Table A3. Mean individual planktonic volume (U3) arranged in order of increasing volume at the sampling stations. 2 May 1970 Station 9 8 6 1 3 Mean 2,006 4,136. 5,706 5,774 6,205 Multiple Range 28 May 1970 Station 9 3 8 l 6 Mean 2,170 3,742 4,474 4,721 5,885 Multiple Range 23 June 1970 Station 9 3 6 l 8 Mean 2,209 5,243 5,251 6,077 6,277 Multiple Range 21 July 1970 Station 9 6 3 l 8 Mean 2,100 3,520 4,867 5,472 7,770 Multiple Range 23 August 1970 Station 8 l 9 3 6 Mean 16,024 21,367 21,907 32,330 32,506 Multiple Range 15 September 1970 Station 9 8 3 6 1 Mean 6,828 11,836 13,312 18,238 19,142 Multiple Range Table A3 (con't.) 10 October 1970 86 Station 9 6 8 l 3 Mean 3,421 6,062 7,475 8,325 8,708 Multiple Range 7 November 1970 Station 9 8 6 1 3 Mean 2,197 4,482 5,537 5,784 7,092 Multiple Range Table A4.Volume (x 10 87 3 of increasing abundance at the sampling stations. 2 May 1970 28 Station Mean Multiple Range May 1970 23 Station Mean Multiple Range June 1970 21 Station Mean Multiple Range July 1970 23 Station Mean Multiple Range August 1970 15 Station Mean Multiple Range September 1970 Station Mean Multiple Range 3 8 /ml) of blue—green algae arranged in order 9 l 6 3 8 0 0 33 59 139 8 9 1 6 3 0 10 295 722 732 9 3 6 l 8 588 3,949 4,008 9,960 28,010 6 9 l 3 8 182 450 564 960 7,605 9 l 8 3 6 19,642 22,432 23,828 68,960 72,340 3 8 9 6 1 4,718 6,623 8,087 8,648 17,163 Table A4 (con't.) 10 October 1970 88 Station 6 9 3 8 1 Mean 2,633 3,992 8,019 9,788 10,867 Multiple Range 7 November 1970 Station ' 9 6 1 8 3 Mean 529 1,429 1,460 5,157 5,462 Multiple Range 89 3 3 Table A5. Volume (X 10 u /ml) of green algae arranged in order of increasing abundance at the sampling stations. 2 May 1970 Station 3 6 1 8 9 Mean 72 75 108 433 685 Multiple Range 28 May 1970 Station 9 6 l 3 8 Mean 434 512 728 3383 3476 Multiple Range 23 June 1970 Station 9 6 3 l g 8 Mean 740 1880 3039 4304 5356 Multiple Range 21 July 1970 Station 6 1 3 8 9 Mean 92 568 826 883 1728 Multiple Range 23 August 1970 Station 3 8 6 9 1 Mean 485 583 738 768 1022 Multiple Range 15 September 1970 Station 6 3 1 8 9 Mean 112 138 224 321 456 Multiple Range Table A5 (con't.) 10 October 1970 Station Mean Multiple Range 7 November 1970 Station Mean Multiple Range 90 9 1 3 6 8 515 574 672 1136 1137 9 6 1 3 8 138 171 193 625 727 91 3 3 Table A6. Volume (X 10 u /ml) of diatoms arranged in order of increasing abundance at the sampling stations. 2 May 1970 Station 6 8 9 3 1 Mean 3759 4957 5863 8418 14,450 Multiple Range 28 May 1970 Station 9 3 1 6 8 Mean 2289 3710 7513 9684 25,803 Multiple Range 23 June 1970 Station 1 6 9 3 ' 8 Mean 1057 1130 1350 1903 6318 Multiple Range 21 July 1970 Station 6 1 9 3 8 Mean 250 286 489 544 670 Multiple Range 23 August 1970 Station 9 1 3 6 8 Mean 483 663 703 738 821 Multiple Range 15 September 1970 Station 1 3 6 8 9 Mean 543 588 608 719 1558 Multiple Range Table A6 (con't.) 10 October 1970 Station Mean Multiple Range 7 November 1970 Station Mean Multiple Range 92 3 6 8 9 l 629 726 1036 1757 2255 l 6 9 3 8 622 777 2226 2557 3825 Table A7. ing diversity at the sampling stations. 2 May 1970 28 Station Mean Multiple Range May 1970 23 Station Mean Multiple Range June 1970 21 Station Mean Multiple Range July 1970 23 Station Mean Multiple Range August 1970 15 Station Mean Mutliple Range September 1970 Mean diversity of phytOplankton arranged in order of increas- Station Mean Multiple Range l 3 8 9 6 .81 .06 .24 3.60 3.79 6 8 1 3 9 .92 .78 .85 3.92 4.11 6 9 3 1 8 .15 .18 .20 4.31 4.48 6 1 3 9 8 .64 .67 .25 4.26 4.65 3 6 9 l 8 .ll .13 .22 4.29 4.30 1 6 3 9 8 .54 .14 .42 4.40 4.45 Table A7 (con't.) 10 October 1970 Station Mean Multiple Range 7 November 1970 Station Mean Multiple Range 94 l 6 9 3 8 3.72 3.93 4.19 4.62 4.64 9 8 3 1 6 3.52 4.22 4.29 4.35 4.56 Table A8. 95 Mean equitability of phytoplankton arranged in order of increasing equitability at the sampling stations. 2 May 1970 28 Station Mean Multiple Range May 1970 23 Station Mean Multiple Range June 1970 21 Station Mean Multiple Range July 1970 23 Station Mean Multiple Range August 1970 15 Station Mean Multiple Range September 1970 Station Mean Multiple Range 1 3 8 6 9 0.108 .128 .238 0.385 0.445 6 l 8 3 9 0.095 .175 .180 0.368 0.423 9 3 8 1 6 0.350 .405 .405 0.478 0.485 9 1 3 8 6 0.373 .413 .440 0.463 0.573 6 3 9 1 8 0.215 .233 .375 0.383 0.403 1 3 6 8 9 0.183 .305 .320 0.425 0.463 Table A8 (con't.) 10 October 1970 Station Mean Multiple Range 7 November 1970 Station Mean Multiple Range 96 1 6 9 8 3 0.263 0.338 0.378 0.385 0.473 9 8 3 1 6 0.313 0.380 0.403 0.503 0.578 M'11111111111111![LilflijiliiiiiiliES