BENTON HARBOR POWER PLANT LIMNOLOGICAL STUDIES PART XXXII ENTRAINMENT OF PHYTOPLANKTON AT THE DONALD C. COOK NUCLEAR PLANT - 1980-1982 James Barres Laurie Feldt William Chang Ronald Rossmann Under Contract With American Electric Power Service Corporation Indiana & Michigan Electric Company Special Report No. 44 Great Lakes Research Division The University of Michigan Ann Arbor, Michigan December 1984 PREVIOUS PARTS OF THE REPORT SERIES RELATIVE TO THE DONALD C. COOK NUCLEAR PLANT Benton Harbor Power Plant Limnological Studies, Special Report No. 44 Part I. General studies. J. C. Ayers and J. C. K. Huang. April 1967. 31 pp, II. Studies of local winds and alongshore currents. J. C. Ayers, A. E. Strong, C. F. Powers, and R. Rossmann. December 1967. 45 pp. III. Some effects of power plant waste heat on the ecology of Lake Michigan. J. R. Krezoski. June 1969. 78 pp. IV. Cook Plant preoperational studies 1969. J. C. Ayers, R. F. Anderson, N. W. O'Hara, C. Kidd. March 1970. 92 pp. V. Winter operations, March 1970. N. W. O'Hara, R. F. Anderson, W. L. Yocum, J. C. Ayers. April 1970. 17 pp. VI. Pontoporeia affinis (Crustacea, Amphipoda) as a monitor of radio- nuclides released to Lake Michigan. C. C. Kidd. 1970. 71 pp. VII. Cook Plant preoperational studies 1970. J. C. Ayers, D. E. Arnold, R. F. Anderson, H. K. Soo . March 1971. 72 and 13 pp. VIII. Winter operations 1970-1971. J. C. Ayers, N. W. O'Hara, W. L. Yocum. June 1971. 41 pp. IX. The biological survey of 10 July 1970. J. C. Ayers, W. L. Yocum, H. K. Soo, T. W. Bottrell, S. C. Mozley, L. C. Garcia. 1971. 72 pp. X. Cook Plant preoperational studies 1971. J. C. Ayers, H. K. Soo, W. L. Yocum. August 1972. 140 and 12 pp. XI. Winter operations 1971-1972. J. C. Ayers, W. L. Yocum. September 1972. 26 pp. XII. Studies of the fish population near the Donald C. Cook Nuclear Power Plant. 1972. D. J. Jude, T. W. Bottrell, J. A. Dorr III, T. J. Miller. March 1973. 115 pp. XIII. Cook Plant preoperational studies 1972. J. C. Ayers and E. Seibel (eds.). March 1973. 281 pp. XIV. Winter operations 1972-1973. J. C. Ayers, W. L. Yocum, E. Seibel. May 1973. 22 pp. iii XV. The biological survey of 12 November 1970. J. C. Ayers, S. C. Mozley, J. C. Roth. July 1973. 69 pp. XVI. Psammolittoral investigation 1972. E. Seibel , J. C. Roth, J. A. Stewart, S. L. Williams. July 1973. 63 pp. XVII. Program of aquatic studies related to the Donald C. Cook Nuclear Plant. J. C. Ayers and E. Seibel (eds.). December 1973. 57 pp. XVIII. Effect of a thermal discharge on benthos populations: Statistical methods for assessing the impact of the Cook Nuclear Plant. E. M. Johnston. December 1973. 20 pp. XIX. The seasonal biological surveys of 1971. J. C. Ayers, S. C. Mozley, J. A. Stewart. December 1974. 181 pp. XX. Statistical power of a proposed method for detecting the effect of waste heat on benthos populations. E. M. Johnston. December 1974. 29 pp. XXI. Bacteria and phytoplankton of the seasonal surveys of 1972 and 1973. J. C. Ayers. November 1975. 153 pp. XXII. Underwater operations in southeastern Lake Michigan near the Donald C. Cook Nuclear Plant during 1974. J. A. Dorr III and T. J. Miller. December 1975. 32 pp. XXIII. Phytoplankton of the Seasonal Surveys of 1974 and 1975 and Initial Pre- vs. Post-Operational Comparisons at Cook Nuclear Plant. J. C. Ayers, N. V. Southwick, and D. G. Robinson. June 1977. 279 pp, XXIV. Entrainment of phytoplankton at the Donald C. Cook Nuclear Plant - 1975. R. Rossmann, N. M. Miller, and D. G. Robinson. November 1977. 265 pp. XXV. Phytoplankton of the seasonal surveys of 1976, of September 1970, and pre- vs. post-operational comparison at Cook Nuclear Plant. J. C. Ayers. April 1978. 258 pp. XXVI. Entrainment of phytoplankton at the Donald C. Cook Nuclear Plant - 1976. R. Rossmann, L. D. Damaske , and N. M. Miller. 1979. 88 pp., plus Appendix of 3 microfiche cards (154 pp«)« XXVII. Phytoplankton of the seasonal surveys of 1977, and further pre- vs. post-operational comparisons at Cook Nuclear Plant. J. C. Ayers and S. J. Wiley. 1979. 92 pp., plus Appendix of 3 microfiche cards (122 pp.). IV XXVIII. Entrainment of phytoplankton at the Donald C. Cook Nuclear Plant - 1978. W. Chang, R. Rossmann, J. Pappas , and W. L. Yocum. May 1981. 106 pp., plus Appendix of 4 microfiche cards (180 pp.). XXIX. Phytoplankton of the seasonal surveys of 1978 and 1979, and further pre- vs. post-operational comparisons at Cook Nuclear Plant. J. C. Ayers and L. E. Feldt. January 1982. XXX. Entrainment of phytoplankton at the Donald C. Cook Nuclear Plant- 1979. R. Rossmann, W. Chang, and J. Barres. July 1982. 98 pp., plus Appendix of 4 microfiche cards (156 pp.). XXXI. Phytoplankton of the seasonal surveys of 1980, 1981, and April 1982 and further pre- vs. postoperational comparisons at Cook Nuclear Plant. J. C. Ayers and L. E. Feldt. December 1983. Siebel, E. , and J. C. Ayers (eds.). 1974. The biological, chemical, and physical character of Lake Michigan in the vicinity of the Donald C. Cook Nuclear Plant. Special Report No. 51 of the Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan. 475 pp. Jude, D. J., F. J. Tesar, J. A. Dorr III, T. J. Miller, P. J. Rago , and D. J. Stewart. 1975. Inshore Lake Michigan fish populations near the Donald C. Cook Nuclear Power Plant, 1973. Special Report No. 52 of the Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan. 267 pp. Seibel, E. , C. T. Carlson, and J. W. Maresca, Jr. 1975. Lake and shore ice conditions on southeastern Lake Michigan in the vicinity of the Donald C. Cook Nuclear Plant: winter 1973-74. Special Report No. 55 of the Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan. 62 pp. Mozley, S. C. 1975. Preoperational investigations of zoobenthos in south- eastern Lake Michigan near the Cook Nuclear Plant. Special Report No. 56 of the Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan. 132 pp. Rossmann, R. 1975. Chemistry of nearshore surficial sediments from southeastern Lake Michigan. Special Report No. 57 of the Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan. 62 pp. Evans, M. S. 1975. The 1975 preoperational zooplankton investigations relative to the Donald C. Cook Nuclear Power Plant. Special Report No. 58 of the Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan. 187 pp. Ayers, J, C. 1975. The phytoplankton of the Cook Plant monthly minimal surveys during the preoperational years 1972, 1973 and 1974. Special Report No. 59 of the Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan. 51 pp. Evans, M. S., T. E. Wurster, and B. E. Hawkins. 1978. The 1975 and 1976 operational zooplankton investigations relative to the Donald C. Cook Nuclear Power Plant, with tests for plant effects (1971-1976). Special Report No. 64 of the Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan. 166 pp., plus Appendix of 4 microfiche cards (236 pp.) Rossmann, R. , W. Chang, L. D. Damaske , and W. L. Yocum. 1980. Entrain- ment of phytoplankton at the Donald C. Cook Nuclear Plant - 1977. Special Report No. 67 of the Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan. 180 pp., plus Appendix of 2 microfiche cards (118 pp.) Jude, D. J., F. J. Tesar, J. C. Tomlinson, T. J. Miller, N. J. Thurber , G. G. Godun, and J. A. Dorr, III. 1979. Inshore Lake Michigan Fish Populations near the D. C. Cook Nuclear Plant during preoperational years-1973, 1974. Special Report No. 71 of the Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan. 529 pp. VI CONTENTS Page PREVIOUS PARTS OF THE REPORT SERIES RELATIVE TO THE DONALD C. COOK NUCLEAR PLANT iii LIST OF FIGURES viii LIST OF TABLES ix ACKNOWLEDGMENTS xii INTRODUCTION 1 Summary of Other Studies 1 Previous Studies at the Cook Plant 2 SAMPLE HANDLING AND ANALYSIS 3 Phytoplankton 5 Chlorophylls and Phaeophytin _a 7 Nutrients 9 CONDITIONS AT TIME OF COLLECTION 10 Temperature and Physical Events 10 Chlorination 10 RESULTS AND DISCUSSION 14 Nutrients 14 Phytoplankton 15 Monthly Variations of Entrained Major Phytoplankton Groups .•. 16 Monthly Variations of Phytoplankton Community Structure 34 Occurrences of Dominant and Co-dominant Forms 34 Numbers of Forms, Diversity, and Redundancy 58 Numbers and Biomass of Phytoplankton Passing Through the Plant 65 Chlorophylls and Phaeophytin a. 71 Assessment of Damage to Phytoplankton 71 Monthly Variation of the Chlorophylls and Phaeophytin a_ 76 SUMMARY 34 LITERATURE CITED 88 APPENDICES 1 and 2 (located on microfiche cards inside back cover) 1 Complete results of microscopic analysis of entrainment phytoplankton samples - January 1980 through May 1982. 2 Complete results of pigment analysis of entrainment samples - January 1980 through May 1982. Vll LIST OF FIGURES Figure Number Page 1 Sampling locations in the Donald C. Cook Nuclear Plant screenhouse e . « 4 2 Settling chamber for phytoplankton sample preparation 6 3 Variation of coccoid blue-green algae numbers during 1980, 1981, and 1982 c 20 4 Variation of filamentous blue-green algae numbers during 1980, 1981, and 1982 22 5 Variation of coccoid green algae numbers during 1980, 1981, and 1982 25 6 Variation of filamentous green algae numbers during 1980, 1981, and 1982 27 7 Variation of flagellated algae numbers during 1980, 1981, and 1982 29 8 Variation of centric diatom numbers during 1980, 1981, and 1982 ' 31 9 Variation of pennate diatom numbers during 1980, 1981, and 1982 33 10 Variation of desmid numbers during 1980, 1981, and 1982 ...... 36 11 Variation of other algae numbers during 1980, 1981, and 1982 . 38 12 Variation of total algae numbers during 1980, 1981, and 1982 . 40 13 Variation of number of forms during 1980, 1981, and 1982 61 14 Variation of diversity during 1980, 1981, and 1982 64 15 Variation of redundancy during 1980, 1981, and 1982 67 16 Variation of chlorophyll a. concentrations during 1980, 1981, and 1982 77 17 Variation of chlorophyll _b concentrations during 1980, 1981, and 1982 79 18 Variation of chlorophyll c^ concentrations during 1980, 1981, and 1982 80 19 Variation of phaeophytin a_ concentrations during 1980, 1981, and 1982 81 20 Variation of the phaeophytin a^/ chlorophyll a^ ratio during 1980, 1981, and 1982 82 Vlll LIST OF TABLES Table Number Page 1 Intake and discharge entrainment temperatures at the time of sampling during 1980, 1981, and 1982 11 2 Monthly variation of nutrients 15 3 Monthly variation of coccoid blue-green algae from 1975 through May 1982 (cells/mL) 19 4 Monthly variation of filamentous blue-green algae from 1975 through May 1982 (cells/mL) 21 5 Monthly variation of coccoid green algae from 1975 through May 1982 (cells/mL) 24 6 Monthly variation of filamentous green algae from 1975 through May 1982 (cells/mL) 26 7 Monthly variation of flagellated algae from 1975 through May 1982 (cells/mL) 28 8 Monthly variation of centric diatoms from 1975 through May 1982 (cells/mL) 30 9 Monthly variation of pennate diatoms from 1975 through May 1982 (cells/mL) 32 10 Monthly variation of desmids from 1975 through May 1982 (cells/mL) 35 11 Monthly variation of other algae from 1975 through May 1982 (cells/mL) 37 12 Monthly variation of total algae from 1975 through May 1982 (cells/mL) 39 13 Occurrence of dominant forms in March 1975, 1976, 1977, 1978, 1979, 1980, and 1981 42 14 Occurrence of dominant forms in April 1975, 1976, 1977, 1978, 1979, 1980, and 1981 , 43 15 Occurrence of dominant forms in May 1975, 1976, 1977, 1978, 1979, 1980, and 1981 44 16 Occurrence of dominant forms in June 1975, 1976, 1977, 1978, 1979, 1980, and 1981 46 IX LIST OF TABLES (continued) Table Number Page 17 Occurrence of dominant forms in July 1975, 1976, 1977, 1978, 1979, 1980 and 1981 47 18 Occurrence of dominant forms in August 1975, 1976, 1977, 1978, 1979, 1980 and 1981 48 19 Occurrence of dominant forms in September 1975, 1976, 1977, 1978, 1979, 1980 and 1981 49 20 Occurrence of dominant forms in October 1975, 1976, 1977, 1978 1979, 1980 and 1981 51 21 Occurrence of dominant forms in November 1975, 1976, 1977, 1978, 1979, 1980 and 1981 52 22 Occurrence of dominant forms in December 1975, 1976, 1977, 1978, 1979, 1980 and 1981 • • 53 23 Apparent trophic preference and abundance of selected diatoms in Lake Michigan 54 24 The annual occurrence of selected dominant diatom forms in 1975, 1976, 1977, 1978, 1979, 1980 and 1981, and 1982 ( 5 months ) 56 25 The annual occurrence of dominant diatom forms with respect to each trophic level for 1975, 1976, 1977, 1978, 1979, 1980, 1981, and 1982 (5 months) 56 26 The annual occurrence of dominant blue-green algae and flagellates in 1975, 1976, 1977, 1978, 1979, 1980, 1981, and 1982 (5 months) 57 27 Comparisons of the number of forms of phytoplankton for 1975, 1976, 1977, 1978, 1979, 1980, 1981, and 1982 ( 5 months ) 60 28 Comparison of phytoplankton diversities for the years 1975 through May 1982 63 29 Comparison of phytoplankton redundancies for the years 1975 through May 1982 « o 66 30 Phytoplankton entrained by the plant during 1976, 1977, 1978, 1979, 1980, 1981, and the first five months of 1982 69 LIST OF TABLES (concluded) Table Number Page 31 Percent of non-incubated sample sets which showed statis- tically significant differences between pigment concentrations of intake and discharge water 73 32 Percent of incubated sample sets which showed statistically significant differences between pigment concentrations of intake and discharge water 73 33 Percent occurrence of statistically significant changes in all comparisons between intake and discharge 75 34 Percent occurrence of statistically significant changes in chlorophyll a concentration between intake and discharge 75 XI ACKNOWLEDGMENTS A study of this scope requires the effort of many people other than the authors • Special thanks are extended to Martha Quenon, Julie Wolin, James Hetzler, and Marjorie Ladzick, who did much of the field and laboratory work for the phytoplankton and chlorophyll analyses, and to Linda Damaske, Janice Pappas , Timothy Henry, Catherine Schmitt, and Pamela Dzialak, who performed the monthly nutrient analysis . Maintenance of the sampling equipment was the unending responsibility of Timothy Henry, William Yocum, and members of the fish and zooplankton labora- tories. Their efforts are greatly appreciated. Thanks are also due to Dr. E. F. Stoermer and the members of his lab for invaluable assistance in phytoplankton taxonomy, and to Tom Kriesel and Bill Scott, of Indiana & Michigan Electric Company, for their assistance in plant- related matters. Finally, we thank Marion Luckhardt, who typed this manuscript, and Dr. Marlene S. Evans and Dr. W. Charles Kerfoot, who reviewed it. Xll INTRODUCTION The Donald C. Cook Nuclear Plant is a 2,200 megawatt steam electric gener- ating station situated on the southeastern shore of Lake Michigan about 18 km south of St. Joseph, Michigan. At full operation, the plant uses roughly 6,300 m-^/min of lake water in once-through cooling of its condensers; the water returned to the lake is 9-13C° above the intake temperature. Entrained phyto- plankton are exposed to potentially damaging heat and pressure (in addition, prior to 1979, the plant used chlorination twice daily for chemical defouling of the heat exchangers and turbine condensers). Because algae form the base of the aquatic food chain, the effects of entrainment are of primary ecological impor- tance. The Environmental Technical Specifications of the plant require an assessment of entrained phytoplankton abundance, viability, and species compo- sition to be made on a monthly basis on samples collected in the early morning, at mid-day, and in the late evening. SUMMARY OF OTHER STUDIES Other power plant studies and pertinent phytoplankton research have been summarized in Rossmann et al. (1977). These studies have shown that phyto- plankton may suffer inhibition or death as a result of condenser passage. Various authors have concluded that temperature rises which can be tolerated by phytoplankton range from 8C° to 11C°, although the actual change that can be tolerated is related to the initial water temperature (the lower the initial temperature, the greater the tolerable rise). If chlorination is also taking place, phytoplankton may be killed outright or suffer varying degrees of inhibi- tion in productivity. In addition, changes in community structure have been 1 noted. At elevated temperatures, communities were observed to exhibit a decreased diversity promoted by a shift from a diatom-dominated community to one dominated by either green algae or blue-green algae. Some evidence also exists which suggests that phytoplankton productivity may be mildly stimulated by mechanical pumping . PREVIOUS STUDIES AT THE COOK PLANT Two major studies were initiated to investigate the impact of the power plant on the phytoplankton community. The first, begun in 1968, was concerned with the long-term effects of the plant on the phytoplankton community. The study included the determination of abundances and species composition in samples taken at both plant-influenced and non-influenced sites. These data established pre-operational phytoplankton trends and variations in the lake against which operational data can be compared. The results have been reported by Ayers £t al . (1970), Ayers et_ al . (1971), Ayers £t al . (1972), Ayers and Seibel (1973), Ayers £t al • (1974), Ayers and Kopczynska (1974), Ayers (1975a), Ayers (1975b), Ayers et al . (1977), Ayers (1978), Ayers and Wiley (1979), Ayers and Feldt (1982), and Ayers and Feldt (1983). The second study was begun in 1975 to ascertain the immediate effects of entrainment on the phytoplankton and to monitor long-term changes in the algal community. This study included the determination of phytoplankton abundance, species composition, and viability in samples taken from the intake and dis- charge forebays. The results for 1975, 1976, 1977, 1978, and 1979 are found in Rossmann et al. (1977), Rossmann et al. (1979), Rossmann et al. (1980), Chang et al . (1981a), and Rossmann et al. (1982), respectively. The results for 1980, 1981, and January through May 1982 are presented here. SAMPLE HANDLING AND ANALYSIS Sampling was conducted on a monthly basis v/ith three approximately one-half hour sampling periods in a 24-hour span: after evening twilight, before morning twilight, and at noon. During each sampling period, fourteen to twenty-one samples were collected; seven from the intake forebay and seven from the dis- charge forebay of each operating unit (Fig. 1). Two of the seven samples from each location were preserved for microscopic investigation of phytoplankton abundance and species composition. The remaining five samples were used for spectrophotometric determination of chlorophylls _a, b^, and c and phaeophytin a. During the evening sampling period, five additional samples were collected from both the intake and discharge forebays. These samples were incubated at the intake temperature for approximately 36 hours and treated in the same manner as non-incubated samples for analysis of the chlorophylls and phaeophytin a. During the noon sampling period, six additional samples were collected from the intake forebay for nutrient analysis. Water was collected from a depth of 5.5 meters by diaphragm pumps through 7.6-cm diameter hoses at a rate of roughly 227 L/min. As the water was pumped, the intake and discharge temperatures were taken and samples were collected in 1-L polyethylene bottles. Intake samples were taken from grate MTR 1-5, except in September 1981 when pump failure at MTR 1-5 necessitated sampling from MTR 1-4. Rossmann et_ al . (1977) and Chang et al . (1981a) established the uni- formity of the sampling locations across the intake forebay; thus the September 1981 samples were included in the analysis without regard to sampling location. Unit 1 uses 2.7 x 10^ liters of cooling water per minute. Therefore, the 5-L chlorophyll sample and the 2-L phytoplankton sample represent approximately a ^ z m -1 m Q. cc s o < 11. 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Monthly abundances in 1982 were less than those in 1980 and 1981, except for February and March. The mean population for coccoid green algae was quite variable between 1975 and 1982 (Table 5 and Fig. 5). There was an increase in mean population density between 1975 and 1976, a decrease between 1976 and 1977, an increase between 1977 and 1978, a decrease between 1978 and 1979, and an increase in 1980 and 1981. Peak abundances in 1980 were in July, August, and September; and in 1981, they were in July. Filamentous green algae were less numerous than coccoid green algae and had a population density above 10 cells/mL in December 1979, and May, June, and December 1981 (Table 6 and Fig. 6). The 19&U yearly average of this group is the lowest for the years 1975 througn 1981. Flagellates were numerous and contributed a large portion to the total annual algal population in 1980-81 (Table 7 and Fig. 7). In 1980, flagellates peaked in April with high abundances through September. A high density in June 1981 was followed by higher abundances than in previous years for the remainder of the year. Total abundances for 1981 and 1982 were higher than in previous years, an indication that flagellates may be increasing overall. Centric diatoms peaked in May 1980 and 1981 and in April 1982 (Table 8 and Fig. 8). They peaked again, but not as much, in September 1980 and 1981. Highest population density from 1975-1982 was in May 1981, thus giving that year the highest yearly mean. Pennate diatoms contributed a large share to the total algal population in each year samples were collected (Table 9 and Fig. 9). They were always low in density in spring, reached a peak in April or May, and decreased in July 23 00 ON 00 0^ O 00 a X 9 O U 00 9s d 9« 30 d -^ ^^ -*> /-^ -^ /-N ^\ /--«' >m^ >-^ s^ ■SiX en m in >m^ >-/ >-/ CM o* C«l CM ^ •^ OO >-/ >«' >m^ •^ r>» C«4 >-/ o r» en -^ fNi en ^ r** a\ CM in •-4 f^ oo sO ^^ /-^ OH p^ <* i >o /«N /-\ i*^ >-^ y-^ y^ m <^ • en • o* CM o\ 00 o% >o • CM CM • o -^ >-^ N.^ N-' en en vO >o CM -* Si^ -* m en NO en CM N.^ >-^ s-<» s.^ 'S^ ^1^ vO >m^ o -* o 00 >o «i en 1** en >o a\ CM o r^ CM »n -^ OO •-4 ^ o -• — < -* OH >-• -♦ r* nO CM >«^ vO >^ O OH • vO OH • OH • in • o «n • CM •^ •>4 CM •-4 OH mmt >ii^ CM >^ ■^ CM >—' OH >-• sO v-' OH S.t' o • • • • -* en m CM r«» en OH *n m OH en r^ en 00 • tn CM vO en o o ^ OH ^ ^^ NO r* • • • • •-4 CM ^ «n en m >o en -«* >0 00 »n CM N-* N-«' CM CM •* en en CM CM ■^ CM 00 r* >o %-•' N-' N-' Nil' >-^ Sm' >.^ v^ v-' Vi^ >o o >o 00 «n o en >0 -* \o OH ^ 00 m o •* »n o sO l*» CM m OH CM *«^ ^^ /-S ^^ ^^ /-^ /-H ^-^ en ^14 OH 00 /-^ >-N «^ ^% CM -* tn -^ en 00 • CM m en -* • • m • • • • 00 •-4 ^ 00 ** OH vO 00 »n 1-^ •^ CM >^ >•«' >^ "^^ >-^ 00 >«^ s^ N*-* ^ ^ en CM «M^ >-^ ^ >i^ -* m tn ^ •-4 •n OH CM »n ^ CM tn OH OH C4 tn en »n "^ »n en >o -* r** — 1 en en /«^ OH .•-s /<-v >-\ /^ ^— <» >^ /-S • vO • vO • • oo • *ii4 ^^ -* NO • CM • NO m • OH • • • • »^ r* o CM CM NO CM r^ yO •>* ^ 'Om^ N^ ^M^ en >m^ «* en en tn r* in OH OH s^ ^ >^ s^ N^ >i*' >^ ^-' s^ OH CM P«» m 00 OH ^ in CM -^ O NO CM CM in -* OH 00 OH m -* en ^ ^ NO '^ p^ CM «N CM CM es CM CM 00 ^"^ ,*^ /*S >-^ ^-s /-^ /-S **-^ • • • • CM • •M* CM •-4 OH 00 00 CM <^ ^ -^ OH • r»» • • • • • • « •-4 CM •^ cn O r^ -* NO NO r* CM in >-• * •ii4 • OH Wi «n Wt u 00 c 1 >s u ^ hi 9> 41 U to 4i fl 41 ja -o >t jS C8 9 XI ^ OB 4) M m a l-» 4J s U a •H 4) >s 9 4J o 4) 4) u a c U3 M M >« S r-l M o. 4J > a es s ^ 41 Am J8 ^ S 9 ^ 5 in CLD M Pb4 25 oo 9i o a* 00 ON CO S 3 O >0 O w d 00 O • • 00 P>. ^— ' ^ o <* a\ <^\ ^ as >» ^ CM CM /-S /^N CM m •^ en en in en -* o cn •«»' r*. li^ 9s 00 • • • • • CM 00 's-' v^ O «^ >-i^ — * en ^ 00 ca ■"m^ r- •n >*• sr N-/ 'o-^ ■w "^ 0^ CM -* CM <^i<' >-' CM •* 00 CM r* >«^ r* OO CM — « p>i CM so ^ en sr CM . sO •-4 o 9s i^% <<-N /"^ >-^ z*^ r*» /-v t/% ^ o »n m -* »n m CM o vO 00 *-\ • m r*» /■-S o m 00 • en o o o • o • • O • • o • "W >*1^ en O -^ CM o >-• •-4 o >m^ o o ^ N^ N-^ d v^ v^ >«^ m •^ >^ ^ N^ tn a\ >o P* >«.^ «* P^ en r* -* nO -* o m o NO en o a\ «n o* CM o •^ J o o o oo ^ o CM m -• O en CM o O ^^ 00 en >^ OH CM en o ^-\ 00 • • o o o o • • o >-• 'W/ o o >-^ 00 o >-^ "^^ a\ r>. o o o -^ CM vO o o 00 en /«^ CM CM o CM m •^ • • o o >--' >— / N«^ 00 o -* CM o en CM p^ so ^-^ '^ o d o d -/ 00 (0 > e 43 -4 r* m m -4 <* CM o m .-n ^.^ en -^ NO /-^ en CM 00 rx. o CM 00 o r** • OO • -4" ..^ >^ 0-t ..^ —4 «l^ CM CM • ■s^ o •s-c •^ >^ ^i^ CM >-/ -^^ ■0-^ ^ >o in •^ ,11^ o CM ■>m^ m CM as N-* CM en o CM r^ vO CM •-« •-4 •-4 -^ • • • CM en CM CM <-4 00 «»« 00 00 r^ y-s CM ^ >-S 00 CM ^^ /«^ -'^ en en en ^ as ^^ 00 o CM r^ NO • p«* o 00 • o\ as o «^ CM CM "W • • -* • • • >m^ N-^ p^ ^ o "^-^ >-r^ vO >o en en —4 ^i^ >^ NO en v-' s^ N-' so CM NO -* as o 00 \0 00 o CM vO 00 -* CM CM o -• vO NO CM -* o a% e /•^ /•> /-s ^-s ^^ s /-S >^ /-^ /*^ ^-s CM ^^ p^ 00 as /•^ CM m o o •-« »n en ^ ^ en ^ nO • • • • • nO ,^ O en -* •i^ CM • CM yr% CM • ^m/ nO CM m4 N-' NO >^ >m^ >• s «^ ^.i^ V*!' N-* N-* 00 N^ r* m CM >m^ ** 00 o en CM r* NO m CM >o 00 r^ m r* »* en as vO »r» -• ^4 -i* in ^ /-v /*% -'-^ o /-S r* ^ o nO /-^ vn NO /-s /*^ >-s <^^ /-N /"^ 00 r** o • en sO CM »-< CM • m r*» CM d • • • o^ •M o ^^ CM o o o •-4 p*. >-<' y,^ >^ Nm^ o >-^ >»/ >-^ >i^ >^ "* NO o 00 o in in en 00 CM 00 m -* '4' • • • • ^ 00 -* o P-4 as o o o CM •^ •^ as o (S 3 CJ •H 4) >^ a. ^ 3 s -< s n •-> ^ M CO o o o 4) > O z s o 4) Q a 26 CI O z: n'ooi ws^ nu/syaauHN 00 c CO 00 ON o 00 bO c ■o CO M a 3 C <3J CO bO C d) Q) U bO CO 3 O c a CO u-i O o CO > o M CS4 27 o ,^«* « 00 CM • • • . 9S sO a» x-* >,^ >m^ Nm^ • • SO nO «n rv -* -^ yO m^ m^ ON „^^ • CM • CM • o vO • o • o o m >o «* m vO m VO CM -^ o • r** • en CM 00 00 CM m4 CM • <7^ NO o • ^^ ^-\ ^N ^^ ^-\ ^^ ^^ /-s '"^ >-s ^^ ^ CM ^-^ -» o • • • 00 • • CM • r* • • 1** m CM ON •^ »n ON NO ON en CM 9^ >o sO cn CM CM NO nO OS CM *• o NO VO -«• J^ *r> ON j*> «n ^ CM fn r^ vO rs. •* vO ON r^ a* -^ en ON CM •-< CM NO 00 -*• CM CM p** -^ »n NO -* ^ "^ cn vO r^ ^ cn -* -^ o 00 ON r* >»• 00 ON ON /-^ i^K sO <<-\ ^s. /-^ <»-> ON • en ON m NO -^ ON fN. 00 -4 CM r<» -^ >.^ — « >-• d NO ON r^ O 9s O 00 ON oo NO ^-^ CM "^ • NO as as 00 00 '"^ • NO o • NO ON -* O «-« NO d en f-4 r>* «^ lO NO — « en cn en ON >-^ a^ s^ 00 o o m r*» NO CM o •««• 00 O CM *^ o en NO rs. o m »n r* -* NO o —4 CM CM CM en cn m r^ m ^-s NO • NO NO en nO CM O • CM cn • CM NO cn o CM CM • o • en • NO OO • o ON • p»» -* • 00 as 00 • CM m CM • 00 NO CM • cn • en • • en en NO • CM in • CM 00 • NO CM • ON «n • CM »n 00 ^^ 00 o 00 CM • cn «-• 00 NO -• ON ® 2 •-4 as CM s 9 JS £ 1 u 2 ^ -^ •♦ r** NO NO O 00 ON m m m NO M 4J a «} CD 0} ja >% d -> -< CO O ON nO U 4> > O z u £ I >« a ^ 0) u U C8 9i « Q >« <0 ^ £ 28 5 i 00*0091 OO'OOZl iu/sa38unN 00 'T3 cd 00 0^ o ON c •H CO § C (U CO 0) bO cd c o CO > M EX4 29 Xi 3 O u i o u CO •H o c o > Q to -•-s '-N ^^ ■"^ ,„m^ "-^ es m c^l • -^ ^ • • CM • ^ • • «* •■14 >* r>. 00 ^ >«/ ^ \^ v** O^ • • c • • -^ — • 00 Sf in o in CM O *-\ ' m nO ^-s ^-N /-N ,*-\ --N 00 -*-s ^--s .^> ^>ms *-> e^4 m sO 00 • »n 00 m • ^ f^ m • • • vO • >* • -^ • • • 00 ■> 00 nO <^4 00 CM >* 30 NO p«l» -* m -^ 00 a* •-4 -^ m .n en >-/ o% sO ^ OH m en • • '^^ • ^ • • • "^ • • • • -* en o 00 O »n o» o o CM o o o en M* i -^ CM 0-4 *^ as mm ^ r>. in CM 00 *«^ >^ ^-^ >-^ >«^ >«^ >-/ >-^ Sm^ 'S^ N^ >-^ ''^^ o^ • • • • • • • • • en xn r** O o o 00 r* o vO r^ 00 o m o en »^ en o ^ ^ 00 o CM r** -\ ^•-K ^^ ^■^ *-> 00 vO e^i • '^ 00 00 CM o en «i4 • a\ • OS • • • • • ^ m m4 • CM o% 00 sO as 00 m -* ^ as >-• 00 >.• CM Si/ 00 * .1^ o 00 <7N ON vO vn ON CM P>« ON >* '^ nO r<» en in CM -^ y-s CM »n CM cn -* r** 00 00 tn • ^ ^O O in p^ en cn O • 00 c5 NO » NO es r^ -* \0 -^ o% en o 00 .^ -^ 00 sf -* en r^ o% >«/ ^ 00 CN| OH NO a* ^ "^ • "^ • '^^ ^ o • • Vi^ ^ • o m en l CM o% o in o o CM o ON NO CM * 00 en r** tn 00 CM as nO —4 «-4 •-4 CM as r* >-^ '**' >-/ N^ >-> N** ' N-' >-/ N^ >*• s^ o\ • • • • • • • • • • • en o* a\ r»* m cn o «* m NO NO r^ en in NO r«* 00 2 ON NO NO -^ r* •i^ ^ as mm —4 cn o 00 ^s • en t^^ • OH ^ 00 ^ • as • r* • OH in NO «M 00 00 nO in in o OH 00 ^ ^ m «n en CM ^4 m ^O in CM ^ >-^ v-' >-^ ^ >m^ >-^ v^ >W1^ >-^ N-* >i^ >m^ r*» • • • • • • • • • • • • cr* o r^ o § CM o CNJ o >* o c^ o >o O en r^ fo» «* O m m 00 o» ^ -# CM en en CM * NO - m o • d"^ • • • • en • en CM m ^^ ^^ m4 o «« r^ o • 00 • • • CM -* 9^ en CM r^ ^ o en QO •-• «* en CM m »4 •^ -^ NO CM -w CM NO CM • • • • • "^ • • • • • • • •^ O O O O O r^ ^ CM o« nO -* s in s o« m as -^ * as CM a CO >% We u u 1 >» u ^ U 4) s M eo jj z JO ^ >% JS CO S XI f^ « a a f4 w 3 l-i u •H Q> >H 3 4-» o 0) « M c C ^ Wi U >s a w 60 o. 4J > o CO s CO £ 2 < s ^ ^ ^ ^ a o s u 5 o c CO 4) 30 00 ON T3 C3 00 O CO ON bO C •H {-I 3 -o CO 0) OO'OOtC 00*0091 "lu/saaaunN 00*008 a o ^3 o 1-4 4J C (U a o o cd CO > M 31 >^ • • • e o\ »n »n o >* fM ^ CM «n en '^il/ >^ CM O 00 c*> O O CM r*<» <^ hn m vO en 00 -^ CM 9t OO -« o -• o in en in m -4 30 ON o ON CM sj- ON O o CM »n — « tn vo 00 vO CM o o r<« 00 -« CM O ON o 00 ON o o 00 ^ y-s o • • • m • • m ON •^ \n ^ sO >o <* •-4 o -:r m^ <*> «n -• CM 00 CM • rn • CM vO • o d • 30 nO • o • • o •-4 O m CM r*» r^ CM 00 >o CM 2 rs. •^ ON vO CM m^ vO CM CO CM CM m •-< CM N^ 00 ■«*• >^ >-• ^-^ 'W ■s^ >^ >«• ^-^ >— ' . CM —* CM " en vO r-* vO 00 ON 3 O >—* o CM 00 /-^ ^ • • CM CM ^-\ /-S in ^--s o • CM -^ O P*» • r«» ON 00 -* r*» nO en vO m^ en m^ >-i^ cn -4 >.• CM NO •-4 -* r* >-*' CM rv ^-^ >^ >-^ >«/ -^ >M' >-<' >-/ ^-^ >^ 00 CM ^ nO o O o -* O o cn CM •-4 ON vO «* CM «n m CM r^ vO r* CO in CM ON • • m " m ON in 1** /-N o -«-\ 00 -^ CM /"^ CM • r^ ON d • • d • m o 00 m CM ^ m m o o m ON N-r' -*• CM >«)' •-4 m N«/ • o O • en • CO • • en • so CM • 00 m 00 «<* 00 r* -* CM CM -* 00 CM rv. cn r*. ^ 00 P^ m NO ^ ^ vO ON /-^ o CO ^-N e ON ^"^ • y-N NO /•-s • • nO • CO OO • ON f^ d 00 o 00 CO NO CM in ON m O «^ NO o -* CM -* s../ >-/ >-» CM Si*' CM »-4 c^ CM • • • • o ^ • CM • s • o • o • 00 • CM • o • o ON NO CM -.^ NO ^ >-s >i^ ^"^ /»-S • • • • • • r*» NO CM «* • nO NO 00 CM CM vO e • • • *i4 ON <* Q r^ o 0-$ *4 CM ^ ^ cn CM N-^ >-* m cn f^ ** CM ^■^ >m^ >M^ >^ N^ OO 00 >^ N*^ >^ s^ N^ o o o o o -<• o in ^ CO r^ •^ NO <« CM ON 00 r^ ON o CO o •-« « 3 .u O 4) 4) c »H bO Q. u > a ^ 9 5 S o o s o PB4 33 through October. Highest density occurred in May 1981, dropped sharply, and remained low until thermal stratification ceased in the fall. Desmids were consistently low in abundance through 1982 (Table 10 and Fig. 10). Maximum population density of 5 cells/mL was obtained in May 1981. No significant change in population was found from 1975 to 1982. The group of "other algae" is composed of phytoplankton which cannot be adequately placed in any of the groups mentioned above. Most algae in this group are green algae. In 1980-81, this group of phytoplankton reached peaks of abundance in September 1980 and April 1981 (Table 11 and Fig. 11). The 1979 mean population density was the lowest in the period from 1975 through 1982. 1981 had the highest mean population density. In 1980 and 1981, total phytoplankton abundance reached peaks in May, September, and November (Table 12 and Fig. 12). In both years, the maximum occurred in May and corresponded with maximums of centric and pennate diatoms, respectively. A maximum occurred in April 1982. High population peaks were also encountered in September, October, and November 1980 and 1981, after isothermal conditions resumed. The mean abundances for 1980 and 1981 were the highest since 1976. Monthly Variations of Phytoplankton Community Structure Occurrences of Dominant and Co-dominant Forms — For this report, any form constituting 10% or more of the total population in a sample was considered dominant. A comparison of these monthly frequencies for the years in which the plant has been in operation can reveal any change which has occurred in the distribution of these species during the period. Those forms which appeared relatively infrequently (less than 50% of the total 34 o 00 >-^ >-<' -*^ N^ 9i 20 o oo fO N-^ CM m r^ 00 9« CM tn CM • • • CM o oo 9^ a z*^ /-\ ---^ /«^ ^> ^> --s /-N ^^ -* r^ oo .^-^ >-s o 9s cn >i^ s^ N-* • >«^ ^ o> r*» v-^ cn CM :n <*> o m o f^ :j CO -4 o* m ro ^ 00 00 >-^ r«« in r** • • • • • • • • • o d CM • • 00 • ^^ /l-N ^"^ .^\ ^-\ CM ^-s >— * >-^ ^^^ ^ p*. oo en ^ >o en m oo P^ •1^ ^ >*^ ^^ O >m^ Si^ >^ nO N^ >^ >-^ -♦ as o 00 r^ vO :n o o o o o o* en in m o 00 -^ •^ -^ vO CM vO m oo m in o« «N O -• o -• CM -• o o o o •^ o m o o m CM ^ /i^ •-4 -^ >o ^^ o o o o o V-^ .>«-» s^ —4 «iii4 OS CM o '^■^ >o en CM >«/ »n "^ en cn o r>. « o o o o CM 00 o cn c5 "*/ en en 00 d ^^ -*% ^-% ^-s vO m m *"S -«-\ m >o f-4 CM «* sO cn •-# «i4 CM CM o CM ^ m o o o o ^^ >•• Ni^ d o >-»' 00 -^ p^ ^^-^ >— ' f>» m -^ «H m cn CM CM in .■^ CM r^ • o o o -* -< O 00 as 3 O m p»* OS d •-4 0) cd m as ^^ ^> /-S CM ^^ ^"^ *-^ CTS m --> /-^ /^ *-*» CM as p»» CM o o -» cn o CM o cn >0 as cn ^ CM /•> ■^ -^ r«« CM • ^ in en vO • • o • • • o • o • >^ >ii^ • o o O O nm' o o o >^ 00 o >«/ >-^ CM >.^ >^ >^ m r*«» o en cn CM (■^ CM o '-^ 00 cn o CM CM o 00 00 CM m O CM (^ o% as -• o o o CM o o >-* J o /-^ r» ^-^ ^^ NO ^^ ^^ CM m ^-s ^N /^k ^^ vO •-4 r>. ^ r^ cn o m r- o tn *^ as »4 CM 'S 00 CM oo • /^^ ^ o • • >-* m • in cn • in • o • • NO CM m s^ ^^ >-» >mf NO o m >-^ sr •* r>» CM m r^ NO >-«' CM 00 o oo "^ CM m CM "^ "^ o o 00 cn -• •-4 -* «^ o J ^-s /■^ z*^ ^ ^^ ^^ /-N ^^ oo CN| /^\ CM /-S •^ m 00 o m as o* CM -♦ cn r»* r^ ON CM in ^ '^ -s CM • • • NO • 00 • • O o ^ >^ >^ • >i^ N-* >-^ 00 r** m Ni^ CM >m^ o m o o r*« ^ cn 2J m «♦ m in r*i. N-^ ^^ o^ 00 • • oo • • • CM • m • CM • o • o o • o • • o in CM o ON CM CM cn -* cn o o o • o • o • o ^ • o • o d • o o >-i/ >m^ N^ >^ s^ N-i* >^ ^^ o 00 oo CM o m CM '* cn 00 m o o o • o • -4 • • CM • CM • o • o • o d • o oo ON c»« e s m 9 u 14 Wl 43 u 4) 4) ■" 44 fl 0) ^ .o >« tt 0) .o a a •H 4» >% 3 4J o 4) 9i ^ >% e •-4 bo a 4J > a 48 2 3 3 3 « a o 4) 4) * t-l o u u 4) >> 4) 3 e « 35 en a 00*6 00-9 os> ooe nu/s«3aunN 00 as CO 00 ON o 00 ON bO c •H CO B C a CO o •H U CO •H }-i CO > o M ^14 36 en 00 o • • • • rM -»- e>4 9^ o* en 00 >^ m en C^ «>j ^ -* •^ s.^ >^ >^ • m e^^ C^ nA CM c^ 00 00 o \n 00 O 00 as a 3 O > M *J 5 e 9« *»— * >-s >0 ^,^ >-s >-* ^^ '^^ /^ /-s ^-s y-s vO m • »n o -^ OO 00 ^ CM • P*» • 0» r»» • • • • • CM tn •-4 CM M« r* ^ r^ >o ^ »n x-' en CM >-' cn CM >iii^ p* Sm^ Ni^ CM N-i* >*^ »^<' N-.' 9« •^ ^ NO .^ «n CM o O m a* ^ »n ^ CM m 09 00 o CM en •■« CM vO -* ^ 00 >o -^ m «^ ^•^ >-> ^^ ^N /'-N ^-K 9« ^^ • • o 00 CM o o ^ CM • o o OO CM m -* M4 try CM CM Vi^ >-^ >m^ NiX -^ M^ >^ >«^ >-^ >•-' >— ' vO v>^ ^ nO CM vO ^ -* o «n o* o» CM vO p* vO r*. O* •^ o o o .•n ON ^ »n vO m CM CM m en >^ — • in ^s 9> 00 >-s CM ^ lO m • en • O* a\ so o N-^ >my >*• cn ><• -* o 00 >-' • -^ ^ CM a> — < OO o* a\ eM —4 NO 00 d CM CM CM r^ ON ON ^-^ ^-s /-^ /— \ cn y^k ^-N y.^ /-\ • O r» • cn cn as «♦ r* m O en • o • • O • ^4 00 r»* m^ -* cn en -^ cn 00 cn o V*' N^ >-<' N-' ^ >o CM CM •-4 CM 00 o* CM NO >-• >-' >-^ N-' nO >■• S.^ Nirt' o en vO r«» ^ o '^ ON >o m CM sr m m vO m o o 00 ^ CM NO ^ m -* CM -< /*S >-N >«^ -^^ /-s -* 00 • vO o p*. !C ^ NO "~* NO o • • • m in o m^ r*» CM vO r>. •ii^ in •^ CM Si^ CM N.^ >-^ CM CM V-i' CM 0^ N*^ CM p^ N-* NO ON N-' >^ o "^i* >-^ ^ >m^ NO r«» in f** en vO CM cn 9k cn o •14 NO m cn ON o NO 00 p>« vO •^ •^ CM «i4 •-• •-* ^-^ ^*^ «««^ /-\ >-\ -* -s -•-s ^-K rf— N >*N m f^ ^'-k • ON . • 00 •^ cn 00 f** f^ NO m o • CM • • • ^ • cn m ^ r* CM CM ON ^ cn r>. as N-^ Ni^ >-» CM in •n CM >i^ Nm' cn en as •-« \^ s^ >-• ^m^ ^-^ rv O >^ a »H O CO 9} 37 cr -J GC 2 i ° I CM 00 00 ON CO V4 0) B (U WD U i g c o >. •H i& 4J CO s cd 1 > o M &b4 iu/sa38unN 38 CM OO ON as • • /^S • • rs. vO vO -^ 00 m C>l 00 m . -* e>< -s ^^ ^— * >*s ^-s »o • • • CM CM o ON OO 00 ^ o OO ON O vO r* m 00 o o ON O CM '^ >o ^O en ON CM -• -* -* tn m CM ON • • ^^ en o • ^ -'S /-\ ^ «-^ en ** • OO rs o 00 r^ €M CM CM <* CM CM CM ON «n »n o 00 ON NO Ni*' CM CM ON 00 >-• N,-^ — < en en o J d d d • o • o d o • d • o ON ON en m rs ON sO en 30 »n m <^ o vO en OO ON CM rs. r* m —4 CM -^ -* en en -« -• -« CM CM -* CM CO X 3 O r* ON /■s • rs» 9\ ^-s .^-s • /-S ^ /-> ^s ^-> ^-^ ^ O • O rs .^ CM en o r>. ^ CM -^ "-4 en p>* ON NO CM rs sr\ o rs CM 00 ^ ■^^ •-4 N«-* cn cn N—' sT CM o tn • • d d d • O o • o • o • o ON NO *5 o •<* CM 00 >o m cn 00 nO o s^ -* vO m 00 CM 00 s» cn yrs in o o •-4 -* -«• f^ cn -• •^ -^ cn m en • ^0 *»-N NO • ON NO • vO • O »n 00 ON 00 o en '^ m ON •^ 00 CM 00 CM CM en CM s^ CM CM S-' CM >^ CN| • o • o d d d • o • O • • o d • o O ON NO «n OO r^ ON s '■^ 00 m 00 00 NO CM -* NO CM 00 cn CM cn -• -• CM CM *^ CM cn ^ CM <0 bo O O O vO rs ON NO ON cn NO m 00 CM m CM nO o 00 o ON ON o ON o o -* «n -• o o o CM ON PS O -^ -« CM s^ -^ n* O ON > 4J a (0 H Ps ON • ON • OO • NO cn • CM • cn >-x OO • 00 nO .^-«N • ON • ON CM ^ CM •-4 «^ O '^ CM o 00 in rs. ON ^ -* CO ^ cn CM ON CM CM CM cn N^ Nt.^ Nn^ N"-* NlM^ >^ x-' N^ s^ >^ >-» >m^ N^ o cn o PS o o CM § o s g S S • O m • o ON • lO ON cn o 00 PS CM CM cn «» p<» CM cn CM cn m in cn '^ -• CM CM CM CM cn 3! O e a m •-J 4) e 3 •n i i! 9 ►n 5 O 0) *-» > o o o z s ^ 01 4) 39 i I 8 OD ^ 05 i 8 a. 00 ON •T3 C C3 <-3 S & 8 E s I a I 8 00 ON o 00 C "H C 0) CO "A -I "I CO o C o cd > iu/sd3aunN OOK C3 M 40 monthly samples) as dominant forms were excluded from consideration. If they were included, the resulting complexity could obscure the existing patterns. The monthly comparisons among the years were made for March to December, when complete data from 1975 to 1982 were available. Data for 1982 were complete for January through May. No samples were collected after May. In March, Tabellaria fenestrata v. intermedia and centric diatoms were dominant in 1975; Cyclotella stelligera and flagellates were dominant in 1976; flagellates, Fragilaria crotonensis , and Synedra f ilif ormis were dominant in 1977; Stephanodiscus sp. was dominant in 1978; flagellates were dominant in 1979; flagellates were dominant in 1980; flagellates and chrysophycean flagel- lates in 1981; and flagellates, Fragilaria crotonensis , chrysophycean flagel- lates, and Stephanodiscus sub tills in 1982 (Table 13). During April, the domi- nant forms were flagellates and Cyclotella stelligera in 1975; Fragilaria crotonensis and Asterionella f ormosa in 1976; flagellates, Fragilaria crotonen- sis , chrysophycean flagellates, and Synedra filiformis in 1977; chrysophycean flagellates and Stephanodiscus sp. in 1978; Stephanodiscus minutus in 1979; flagellates and Asterionella formosa in 1980; Asterionella f ormosa in 1981; and chrysophycean flagellates, centric diatoms, and Stephanodiscus subtilis in 1982 (Table 14). The dominant forms for May were Tabellaria fenestrata v. intermedia in 1975, flagellates in 1976, flagellates in 1977, Melosira granulata in 1978, and flagellates and Asterionella formosa in 1979; Asterionella formosa and Melosira granulata in 1980; Stephanodiscus subtilis in 1981; and chrysophycean flagellates, Fragilaria crotonensis , and Tabellaria fenestrata v. intermedia in 1982 (Table 15). In June, the dominant forms were flagellates and Tabellaria fenestrata v. intermedia in 1975, flagellates and Dinobryon divergens in 1976, Fragilaria crotonensis in 1977, and chrysophycean flagellates in 1978 41 CN ON I c CT3 00 O ON ON 00 ON On in ON u o c CO c e o o a> u c CD u 3 U u O TO H CN 00 ON 00 ON o 00 ON ON CO r^ 0) 0^ u i-H C (U }-t v^ 00 a r^ U ON CJ 1— 1 o ON CJN oo^foooO'—''— 'OONinoo CN m o o 00 OOC7NOO^-^ O CJ f-H CO o C >^ < O CO 0) 4J CO a; CO CO • ^\ •H 0- u co CO dJ 1— t CO CO r- 1 x: 1-^ OJ a r— 1 c CO QJ o O 4J •f-4 ^ O »-• a .— t OJ e o 4J o >^ CO o O < o c o c c 0) a; u d) r-l PQ U CO > O c :3 CO O 4-> CO T3 O 4-» c 0) CJ co CO O 3 u o o CO • l-l CO TD • l-l O }-l C CO CO f— 4 ^ •H O- W) o; CO 4-» J-< cn fe co 01 u CO CO c CO o; u a o CO u x: CO CO •r-« D r-4 4J •H 3 ^ C JOi H 3 6 CO CO 3 o CO T3 O C CO x: CL CO CO 3 3 u o CO CO oH •r-l TD TD O o C C CO CO JC ^ a Ou QJ o; 4-J XJ cn cn CO >^ c o r— I O U o G P CO O) CL B CO CO -TS CO u-^ O •H o c 4-) CO CO }-• ^ >^ (D a O rn CU CO B u C 3 CO < Z 42 13 c CT3 00 On O 00 ON ON 0^ 00 ON in ON 03 B o c CO O (1> u c D a o O ^3 H 00 0^ 00 ON O 00 ON ON CO r^ 0) ON u .— t c a; u u 00 a 1^ u ON o i-H O r^ r^ 0<^l^OOOOC^lOOOOOvO o o ^ r-4 O fe CO U CO CO CO CO CO CO •H D D a D V4 o o u o 0) CO CO CO CO CO •H •H • H •H ^ TJ T3 TJ T3 a O o O o CO c C C c o CO CO CO CO ^ jr 4= x: X Pu CL a CL a B OJ 4-> CO p CO f-H 5 •H r— 1 O ■o (D c OJ W) ^ B CO c u f-H OJ 4J U-l m c c >. • IH CO c a; o CO CJ f-H •H >^ o i^ X a CO a f— 1 o c •l-l CO a> W) >^ OJ CO u u u -C O fc o • l-t CO •r-l •H -o B ,—1 u a; o t4-l UH c •H ^ C o o c c CO B o 4J f— t CO O -H U t3 V4 4J c CO CO 1 TD no o 0) 0) c C C ^ >. >» c CO CO :d CJ CO N U C CO 4= CO u CO •H T3 O C CO 0) CO c 3 a; o iM CD •i-l CO T3 • H O V^ c CO CO r— 1 ^ f-H o- OJ OJ ^ 4-» CO CO H 0'-'OOcMOO CO 0) f-H a B CO CD u B o 43 CNI 00 ON c CTJ 00 On o 00 ON ON ON ON CM 00 ON 00 ON o 00 ON ON en r^ (U ON o »-H C <3J U u 00 r^ u ON u T— 1 o r^ r-- ON OLTil^^OOOOOOOOOr^OOOCNO 00 O^-^O^^OOOOOO^H O— 'OOOOO ^ OCSlOvOOOOOOOOOOOOOOOOOin 00 ,-H^OONOOOOOCMOOOOOOOOCO CNJ 0 u c a> u u o o u o H o o o ^ m OOOOOOOO CM ON 6 V-i o u a c en >^ o CO c <: CO > c CO I5 •H CO o CO 4J c C CO ^ (U U c c 4J D o CO ^J 0) •» o C • B !-• o; a o o u-i CO CO CO CO CO 0) CO •r-l •H •H J-) CO T3 }-l u CO C CO CO f—i o a r-^ r-4 r-t B •H • H r— t QJ o ^ 60 CD bO u 4J CO jOi CO ^ c V^ CO r— 1 o cu fe H ^ O o CO o CO H • H 4J 1— 1 a» • •-1 c U e CO H u r— 4 W) a- CO CO •H CO 4J O ^ B D u CO o CO 3 o CO 'f-i T3 O C CO JC CI. CO CO a u CO O C CO u CO x: Ou CO O a B o o CL CO CO 0) CO c CO ^ u x: o co CO C • i-i CO • 1-4 ^ ns CO .—1 f— » 0) u^ c c CO a; U j-» bO CO o D- •H CO co 6 a; }m f— ) >^ o a C (4-( e o •H CO r-l 1— 1 CO o «i-l o V4-4 O CO C CO U J5 }-i U T3 O X3 (D OJ c OJ ^ C ^ C e >> c >^ D C/3 p C/3 :z 44 (Table 16) • Because no sample was collected in June 1979, there was no informa- tion on dominant forms available for this month. The dominant forms in June were Fragilaria crotonensis and Melosira granulata in 1980; and chrysophycean flagellates in 1981. In July, Cyclotella stelligera , Dictyosphaerium pulchel- lum , and Gloeocystis sp. were dominant in 1975; no forms were dominant in more than 50% of the total samples in 1976; Cyclotella sp., Cyclotella comensis , and Fragilaria crotonensis were dominant in 1977; Fragilaria crotonensis and Scene- desmus bicellularis were dominant in 1978; and flagellates, Fragilaria croto- nensis , chrysophycean flagellates, and Anabaena f los-aquae were dominant in 1979; chrysophycean flagellates, flagellates, and Qocystis sp. in 1980; chryso- phycean flagellates and flagellates in 1981 (Table 17). In August, Anacystis incerta and Chromulina parvula were dominant in 197 5; Fragilaria crotonensis was dominant in 1976; Anacystis incerta and flagellates were dominant in 1977; Fragilaria crotonensis was dominant in 1978; Fragilaria crotonensis and Anacys- tis incerta were dominant in 1979; Anacystis incerta and flagellates in 198U; and flagellates, chrysophycean flagellates, and Cyclotella comensis in 1981 (Table 18). In September, Anacystis incerta and flagellates predominated in 1975; Fragilaria crotonensis did so in 1976; Anacystis incerta and flagellates did so in 1977; Anacystis incerta did so in 1978; Anacystis incerta , flagel- lates, and Melosira granulata did so in 1979; Anacystis incerta and Melosira granulata in 1980; and Anacystis incerta and Cyclotella sp. #6 in 1981 (Table 19). In October, Anacystis incerta , flagellates, and Gomphosphaeria lacustris were dominant in 1975; flagellates were dominant in 1976; Anacystis incerta , Fragilaria crotonensis , and flagellates were dominant in 1977; Anacys- tis incerta , Gomphosphaeria lacustris , and Melosira granulata were dominant in 1978; Anacystis incerta and Gomphosphaeria lacustris were dominant in 1979; 45 00 ON 00 ON inOOOOOOOOOOOCNOOOOO ID c o 00 ON o 00 ON CM O O O O C^vOOOOOOOOl I I ON ON 00 ON ON ON 1^ ON CO -H a; u c a; 00 U r^ U ON CJ u o ON I I I I I I I I I o o o OOOOOCScSr-HOOOOcNOOOOO CsimOOO'-^'-^OOOOOOCNr-^^OOO ON ON -HOoooo^o^^mONoooooo in ON c in ON ONO^CNCM'-^CNCNJOOOOOOOOOO g u o c CO c 6 o T3 o c a; u u o u u o vO H o CO 0) a; cd T3 u 0) CO > CO u u CO c CO 01 CO H CO c o CO o CO too CO u c CO D o CO •H o c CO CD CO u c g }-4 o o CO o u a; u c CO >^ a CO c <: CO H V4 CO u • l-l CO CO D C o 0) CO c r— 1 o u CO o F-l }m u o a; CO a CO O a e o o too CO e . D cu •u CO CO too 0) C J-J o CO a CO u CO > 3 C 01 s CO § C o o; •H too V^ u CO (D > > CO •H ^ TJ c o >^ o c I— I CO 01 C too «0 CO to€ c o >^ u o c c CO 0> o >^ o CO >^ U SI cu CO CO CO •H .-» TJ CO «— < OJ r— 1 a; CL rH c o o; o 6 u •r-l CO o }m •H f-4 o; }M O ■u 0) >% CO S u < o C ^ c 3 ^ CO >^ 4J CO C CO 01 O r-l f— 1 r-l 3 a o C e u CO CO U CO c too OJ 4-4 0) CO o v^ J-i too 'H u CO dJ (U O ^ D f— 1 g r-l o; 3 PQ S 52 46 00 c CTJ O C30 ON ON ON 00 o> ON Ov o> r— < e o c c • 1-1 E O T3 a; u c 01 u u o o u o CO 00 ON o 00 ON as ON CO •—! a; o c 0) 00 U 1^ >-< ON u u o ON -HOoo^ooo^ONomoooroooooom^oo cs cncoooooooocor^ooooo OOOOOOOOO— ^cnoOOOOOOOOCNOOOO OOOOOO^OOOOOr-iinom-HOr-HOOOOO O CM O O O CN OCSICNCJNOOON— i^^ B ^ U u CO CO o c c fe < < a CO B O CO o; ^ U 0) r— I CO o- .—I D C -^ CO V-i (U ^ >» u u o X •-< a CO CO c c u ^ 5 •H o o c c c o ^ ^ •u • C CO c u a P 4J 3 c CO CO CO •* 1— 1 «\ f— J CO E 3 73 CL D O C •i-l , O 4J CO CO O CO CO CO }-i q; u • H •H •H 60 4J u ^ T3 T3 CO o CO O CO f-H O >^ C O V- r-l u CO •H .f-1 CO u • 4-* Pu CO CO 01 c CO 0) iJ CO C a > •-• O r-H C CL ^ D C V4 D TD CO - D >. cr c o B O r^ U r-l (U c c O) g V-I 60 CL CO C CO O) >^ O) CJ V^ o o o CO a> r— I a B CO CO O u g 47 00 X3 C CO O 00 ON ON c^ 00 1^ On 0^ CO u o c CO C •r-l e o T3 a c u u c 00 CO 00 o 00 ON CO «-H u c '-• • 0) c u 1 CO U CO (U a o CO <\) CO 3 CO • 1-4 4-) CO c >> ^ O cr CL V4 CO •H CJ u f-H . - ^ r ^ CO "M-l S CO CO cOf •H CD CO CO CO , 3 c Xi r-H 4-» u •r-l •H • H CO r— 1 •H CL f-< CO CO 4-) 4-> 4-1 C f-l 1— 1 CO ^ I—I CO CO CO OJ % >^ >% CO c s X o o 01 O U U rO 0) o a 1— 1 (L» txO CO CO CO CO s u € o O CO c C c C W) s: o >. r-H f— 1 < < < -H CO o CO V4 l-l •f-l r-l CO CO CO c r-4 4J f-^ c o q; CO 3 a; 4J bO U txO c o CO 4J C o c f-* CO CO u CO VM (U 4J o r-l c U v^ a- C OJ 0) o CO M-l }-l . CO O- ••-• CO U CO CO U 3 C >^ CO o rC M P- CO O r-H CO r-l >> OJ U Xi x: CO 13 CU C •H B u » CJ C O CO u a; 4-> C o (D rH C O O ^ CO c c ^ ^ 3 CO C r-l 3-3 •» erH CO CO O >-• c c: CO o) cu o (U 0) f— I V4 V-i 0) o o s CO (L) r-l a e CO CO U-i o }-» I z 48 00 13 c CT3 00 ON O ^ vO vO O 00 ON O 00 ON O — I vO VO .-H r— I f-H ON 0^ 00 ON ON On CO u c J o CO V4 •H u V4 o CO u CO C 60 CO U CO a CO o Cl B o CO OJ CO • H CO rH 4J CO CO s ^^ u 3 . CO W) o O CO CO f— 1 f— 1 C a; 1^ < S co CO CO c O 6 o u u O CO O c 3 CO U CO 3 O u o u o >^ u o PQ QJ B u QJ •u C c • l-l a CO s u o CO CO •H i-H U c CO c f— 1 •f-l 5 u o (U CO f— 1 o CO •u W) • H a c V4 • o CO vO CO 3 ^ JJ CO a c •—1 CO =**= C ^4 c CO % CO u cr >% M-l CO i-> co % 4-1 >% CO r—l rH 3 f— 1 • H ^ o CO J3 •H r—l r-l r-l o }^ O o >^ CL 4-t XJ 0) r-l V-i QJ O CO >^ O O c c f^ QJ CO 01 >^ CJ f— 1 f— 1 (U 01 QJ X) ^ O u CO u u s 0) pjQ £ a 1— 1 ^ C >% >^ W) J-< CO 3 en O CJ < o U <: O H Z 49 Anacystis incerta and Tabellaria fenestrata v. intermedia in 1980; and flagel- lates and chrysophycean flagellates in 1981 (Table 20). During November, the dominant forms were flagellates, Anacystis incerta , Fragilaria crotonensis , and Cyclotella comensis in 1975; flagellates and Cyclotella sp. in 1976; flagel- lates, Anacystis incerta , and Gomphosphaeria lacustris in 1977; Anacystis incerta, Fragilaria crotonensis , and Gomphosphaeria lacustris in 1978; flagel- lates, Anacystis incerta , and Gomphosphaeria lacustris in 1979; Anacystis incerta and Tabellaria fenestrata v. intermedia in 1980; and flagellates and Stephanodiscus subtilis in 1981 (Table 21). In the month of December, centric diatoms and Cyclotella stelligera were dominant in 1975; Fragilaria crotonensis and flagellates were dominant in 1976; Anacystis incerta , Gomphosphaeria lacus- tris, and Tabellaria fenestrata v. intermedia were dominant in 1977; Gomphos- phaeria lacustris and Anacystis incerta were dominant in 1978; Anacystis incerta and Fragilaria crotonensis were dominant in 1979; Anacystis incerta and Tabel- laria fenestrata v. intermedia in 1980; and Fragilaria crotonensis , flagellates, and Stephanodiscus subtilis in 1981 (Table 22). No consistent trend of change in dominant species was observed in the monthly comparisons during the years 1975 through 1982. However, if the data are tabulated for those diatoms which are associated with an identifiable trophic level (Table 23), certain patterns of total annual occurrence for the dominant diatom species emerge (Table 24). These patterns are summarized in Table 25. The occurrences of mesotrophic species not tolerant of nutrient enrichment continuously decrease from 34 in 1975 to in 1982. On the other hand, there has been an increase from 47 in 1975 to 79 in 1982 in the occur- rences of mesotrophic species which are tolerant of moderate nutrient enrich- ment. The highest numbers of occurrences were in 1977 and 1980-82. The highest 50 00 ON c CO O 00 ON ON ON 00 ON 00 0^ O 00 in ON o XJ C CO e 5-1 O c CO c e o T3 O C O o o Csl CO H o> r^ 0^ CO ^^ 01 u c 0) 00 ^. r^ V-t ON a r-H u o ON in ON o^^^inoo^oovoooo^foo cn oinooLnooooovoo^'-H oo r— (inoooNOooomooooooo oo •"• I— H Ov000cn0^00f*^0000000 00 ooooocnoooooO'-H^'-^ooo cn omcNjONCNioocNr-^ocN'-Hooooo cm oo-^oovomooooooooooo o s o s D ■u CO CO o •H •f-4 CO f— 1 C a (l> D CO C }-i 4J o 13 M 4J CO Q) D O u cr C u •H CO e CO ^ •i-l ^ O O dJ O f— I o a CO )-i > CO f-H CO f-l u O) CO W) M CO u r-t CO CO M-l • ^ M-l o; CO a U •r-l CO >. U CO •H JC CO •H Vh a >^ 4-> CO o u CO r— ( CO O >> •-H >^ ^ to XJ c o CO CO ,—4 UH • fH o o j-> u CO u >^ c 0) U OJ ^ CO 0) e C Vj 3 < o IZ 51 00 13 c 00 O •— ' CN •— I r- 1 o 00 0^ O 00 ON r-< O 00 ON ON 00 ON w QJ u C 0) Vj }-• D u o O ON On 00 ON On r-H O a^Om o !2 in 0^ r^r^ovO^H CO CO CO u 3 CO •H r-l • H u u O 3 r-< CO r-4 CO •H CO c 4J «H OJ CO 01 c rH D M D ■U CO CO CO CO e>o Q) a o c • C ^ • p^ v^ o •H CO CO c D CO a a •H D CO u B .— ( CO 4J f-^ o V4 .-^ CO B CO c CO u CO 0) u M-l u '^ #k (U 0) o • S f— 1 0) o CO CO S CO CO CO s • c M-) a V-i O- o c M d •H o 3 3 3 o o- o; CO ^ •H § ^ -d T3 T3 T3 f-4 r-l •H 0) XJ CO M-l CO •rH ■g. Vh f— » Ou O O O r— 1 •-H V4 c CO •H o r— 1 4J CO f— 1 CO o c c C 0) 0) CO o >^ 4-1 r— 1 CO o r— • a; O •i-i CO CO CO ^ AJ f— 4 •H U CO U 0) >» CO •i-l C x: >-• x: x: s: o o r— t u o >. ^ tc a; a 4-i a CL a 1— t f— < OJ d) a; O ^ CO CO ]m CO B S c d) OJ o; u u ^ 4-1 o CO g r-^ c M 6C o o u 4J 4J >% >^ CO CO r— 1 c 3 fe <: fe < o o zn c/ii C/3 o CJ H < o <: !Z 52 00 T3 c CO 00 ON o^J-ooocMoooocNom^fooooo-Hr^ino oo o 00 On o 00 ON OCNOOOCOOOOO'-^OOOOOOOCNOOO^ 00 ON ON CO a> o c CO c o a CO u CO O) CO M-l CO U r-H CO r— I r-4 too 60 CO CO r-^ V-l CO CO 0) CO 4J •H CO r-H f-^ • H f-H iJ 0) ^ 60 D CO CO «— 1 -_ M-4 CO iJ CO CO a; 1— 1 i-H D a C e CO CO U CO 60 M-l CO O }^ •f-i V^ CO a> o Xi r-H B q; 3 ;s z 53 Table 23. Apparent trophic preference and abundance of selected diatoms in Lake Michigan.^ Selected Diatoms Trophic Preference Ml M2 E EI Cyclotella comta (Ehr.) Kiitz. Cyclotella operculata (AgO Kiitz. Cyclotella ocellata Pant. Cyclotella kuetzingiana Thwaites Cyclotella stelligera CI. n. Grun* Melosira distans (Ehr.) Kiitz. Melosira distans var. alpigena Grun. Melosira islandica 0. Mull. Tabellaria fenestrata (Lyngb . ) K'utz. Tabellaria flocculosa (Roth) Kiitz. Rhizosolenia eriensis H. L. Smith Stephanodiscus transilvanicus Pant . Synedra ulna var. chaseana Thomas Cyclotella michiganiana Skv. Asterionella f ormosa Hass . Fragilaria crotonensis Kitton Stephanodiscus alpinus Hust. ex Huber-Pestalozzi Stephanodiscus minutus Grun. ex Cleve and Moll. Stephanodiscus niagarae Ehr. Stephanodiscus hantzschii Grun . p M P M M P P M P P M P M M M p M P M P p M P p M p M p M P P M P P M P P M P P M P M P M (continued) Symbols: 0, oligotrophic; Ml, mesotrophic but intolerant of nutrient enrichment; M2, mesotrophic and tolerant of moderate nutrient enrichment; E, eutrophic; EI, recently introduced eutrophic species; P, presence of species; and M, apparent maximum abundance of the species. References: Holland (1968, 1969); Stoermer and Yang (1969, 1970); Holland and Beeton (1972). (Courtesy to Tarapchak and Stoermer). ^Tarapchak and Stoermer (1976), 54 Table 23. (Concluded). Trophic Preference Selected Diatoms Ml M2 E EI Synedra delicatissima Lewis Synedra ulna v. danica (Kiitz. ) Grun. Synedra ostenfeldii (Krieger) A. Cleve Synedra f iliformis Grun. Amphipleura pellucida (Kiitz.) Melosira granulata (Ehr. ) Ralfs Melosira granulata var. angustissima Mull. Fragilaria capucina Desm. Fragilaria capucina var. mesolepta (Rabh.) Grunow Fragilaria construens (Ehr.) Grunow Fragilaria intermedia Grun. Stephanodiscus tenuis Hust. Asterionella bleakeleyi Wm. Smith Diatoma tenue v. elongatum Lyng. Stephanodiscus binder anus (Kiitz.) Krieger Stephanodiscus subtilis (Van Goor) A. Cleve Nitzschia dissipata (Kiitz.) Grun. Coscinodiscus subsalsa Juhl.-Dannf. p M P p M P p M P p M P P M P M P M P M P P M M P M P M P M P M P M M P M 55 Table 24. The annual occurrence of selected dominant diatom forms in 1975, 1976, 1977, 1978, 1979, 1980, 1981, and 1982 (5 months). (See Table 23 for definition of symbols Ml, M2, and E). 1975 1976 1977 1978 1979 1980 1981 1982 Stephanodiscus minutus (E) Fragilaria capucina (E) Stephanodiscus tenuis (E) Stephanodiscus subtilis (E) Diatoma tenue v. elongatum (E) Fragilaria crotonensis (M2) Tabellaria fenestrata var. intermedia (M2) Synedra f iliformis (M2) Asterionella formosa (M2) Cyclotella stelligera (Ml) Cyclotella sp. Cyclotella comensis (M2) Melosira granulata (E) 2 8 17 3 11 2 1 4 4 1 2 43 11 1 17 52 54 48 40 48 18 58 30 1 16 6 38 43 21 20 5 17 2 3 22 34 13 34 11 1 3 12 9 13 12 11 23 28 13 53 Table 25. The annual occurrence of dominant diatom forms with respect to each trophic level for 1975, 1976, 1977, 1978, 1979, 1980, 1981, and 1982 (5 months). (See Table 23 for definition of symbols Ml, M2, and E). 1975 1976 1977 1978 1979 1980 1981 1982 Mesotrophic, intolerant of nutrient enrichment Mesotrophic, tolerant of moderate nutrient enrichment Eutrophic 34 11 7 70 92 57 62 125 74 79 8 13 28 30 56 58 11 56 number of occurrences of eutrophic species was in 1981. A combination of decreasing occurrences of mesotrophic species that are intolerant of nutrient enrichment and of higher occurrences of eutrophic and mesotrophic species toler- ant of moderate nutrient enrichment illustrates the continuing eutrophication of this region of Lake Michigan. Important trends have been observed between 1975 and 1980 in entrainment assemblages (Table 26): 1) a doubling in the occurrence of the blue-green algae Anacystis incerta , Gomphosphaeria lacustris , and flagellates; 2) a large increase in the number of occurrences of chrysophycean flagellates; and 3) the continued increase in occurrence of dominant blue-green algae. The mechanisms which cause these changes are presently unknown; and, from the information available, it is difficult to offer a good explanation. Nevertheless, further study of these species may yield considerable insight into the factors influenc- ing these changes. In 1981, there was a marked decrease in the blue-green spp. of Anacystis incerta and Gomphosphaeria lacustris , thus decreasing the dominant blue-green algae. Table 26. The annual occurrence of dominant blue-green algae and flagellates in 1975, 1976, 1977, 1978, 1979, 1980, 1981, and 1982 (5 months). 1975 1976 1977 1978 1979 1980 1981 1982 Flagellates Chrysophycean flagellate (sp.) Anacystis incerta Gomphosphaeria lacustris Dominant blue-green 43 71 57 32 95 90 108 41 1 4 24 23 27 19 73 64 42 33 57 83 85 90 35 2 24 13 24 49 48 37 16 9 66 46 81 132 133 127 51 11 57 Numbers of Forms, Diversity, and Redundancy — When working with complex and variable assemblages of phytoplankton such as those appearing in entrainment samples from the nearshore of Lake Michigan, it is advantageous to use some quantitative measure of the distribution of popu- lations within the various assemblages. Such measures can furnish information for assessing changes in community structure. The quantitative measures employed in this study are the number of species, diversity index, and redun- dancy. The diversity index is calculated using the formula presented by Wilhm and Dorris (1968): _ S d = - Z (n-|_/n) log2 (n^/n) i=l where S is the number of species , n is the total number of phytoplankton in cells/mL, and n^ is the number of phytoplankton of the ith species. As not all forms encountered can be identified to the species level, the diversity index presented may differ somewhat from the true diversity measure. Redundancy is a measure of the dominance of one or a few species within a population assemblage. As presented by Wilhm and Dorris (1968), it is: ^max " ^ r = ^max "" ^min where d is the diversity of a community as calculated above, d^^^ ^^ ^^^ maximum diversity for the community, and d^^^ is the minimum diversity for the community, ^^niax ^^^ ^min ^^^ computed as follows: 58 ^max = (l/n)(log2n! - Slog2 [n/Sj!) dmin = (l/n)(log2n! - Slog2 [n-(S-l)]!) The possible values of r vary between and !• When an r equals 0, it indicates that all the species encountered in a community have the same abundance; where- as, when an r equals 1, it implies that one species dominates a community. As shown in the formula, this value is derived from the measure of species number, abundance, and diversity. The number of forms in the 1980 and 19bl entrainment samples showed a bimodal variation. The primary peak in 1980 was in September, with a lesser peak in June (Table 27 and Fig. 13). The number of forms varies from 41 to 7U, with the minimum and maximum corresponding with the months of July and Septem- ber, respectively. In 1981 the phytoplankton peaked in March, May, and Septem- ber, with 66 forms in March and May and 65 forms in September. The minimum number of forms was 40 in July. Species number fluctuations have long been an important issue. Many theories attempt to explain this phenomenon. The one offering the simplest and most plausible explanation for this was proposed by Moss (1973), who explained that different species begin to divide at different times of the year depending on their specific requirements for light, temperature, and nutrient types and levels. Most of these species are probably present in at least very small numbers throughout the year, and from these inocula larger populations can develop. After growth of a large population, decline occurs as the number of cells returns to the inoculum level. Population size depends on the balance between growth and concomitant loss by sinking, parasitism, and grazing. After the peak population has been reached, there is a rapid initial decline. As some 59 00 ON NO CS ^ «-4 *<-4 NO d CM ON ^ ON I ^-' I CN I ON o NO CM CM CM w4 CM 00 00 CN CO -4 CM NO ir> ON CM 00 ^ r* NO CO 00 CO 5 ON NO 00 CM in m O in U 0) CO m oj ON iJ ^ c QO U U CO CO CU o ■u oj O t3 o c a O (U 4J GO CO x: a o c >v o en O en o 00 ON ON en in en 00 00 in CM m ON 00 NO en en -4 -. -. ^ -. -^ en -H -. CM en r^ NO rx. « 00 o 00 SO -^ m O -3- ON in NO NO m 00 en CM en 00 vO NO vO in vO CM in -< CM CM 00 O NO St CM O p»» cn en <3N en m CM o ON o in CM ^ -4 en Cvl ^ 3 -• 00 3 3 i cn > o z ON vO ON ON c CO a ^ a; u O CO 0) (U O >4 60 o cr Lu m r: 3 " 5 -• « -I -' 5 a. I J" •• i ■■i .. I flO kU > s 8 a. " ^ " s QD mnu. -i 00*09 OO-SS OO'OS sudOi dO diauriN — I oo'se CM 00 ON cd 00 o 00 ON bO c •H M CO S o M-l o a C o u Cd > O M CS4 61 populations decline, others grow; and, with time, the complexity of overlap increases, leading to progressively greater diversity. This hypothesis seems to explain why the number of forms increased rapidly in late spring, late summer, or early autumn after an initial decline in spring and summer population. This hypothesis alone cannot fully illustrate all the changes in the system because the species fluctuation is also governed by many biotic and abiotic factors which vary from year to year. However, the increase in species numbers in summer has often been associated with upwelling which makes available hypolim- netic nutrients, including orthophosphate and silica, which stimulate the growth of some forms (Rossmann et al. 1979). The diversity index is an estimate of the structure of communities. It measures the degree to which individuals are represented in an assemblage and is determined by the number of species and the degree of apportionment of individuals among species. For example, a diversity index varies with (1) large numbers of species, or (2) a high degree of apportionment of individuals among species, or (3) both of the above. In 1980, diversity reached its maximum in June and its minimum in August, corresponding with the values 4.16 and 3.58, respectively (Table 28 and Fig. 14). In 1981, the maximum was in May and the minimum in June, with values of 4.83 and 1.93, respectively. For both years, the minimum values do not coincide with the time when the minimum number of species occurred. The number of species does not always have a strong influence on the diversity index. This is because the diversity index depends on not only the number of species but also the codominancy of many species. Therefore, it is not uncommon that a sample with a high abundance in which one species is dominant has a relatively low diversity value. In fact, the cases of September 1977, October 1978, and September 1979 illustrate this situation: a large 62 x: 01 ac w 3 0) £ u J-i s: c ■u a; u LTi «0 r^ a. > J= c CO o i-l OJ JU c a. CO S en a Cfl 4^ -o >> c JZ CO a. to 04 HI CO P-- 00 vO 00 oo d- 3- o o ^ CN m in o ON in o CO vO O o CM CN vO O 00 CO o -^ ON o CM 00 O NO o vO ON o CN CN en o CO CO NO 00 o O in CN ON 00 >3- ON vO ON NO CO a- 3- XL „,-^ ^-^ CN r^ -J- r*. 00 ^^ in CO ON 00 ON 00 CN -3- in in CN 00 vO NO 00 CO a\ ON o o d CN o o "^ ""* ^^ o o m o ,^ SO r- CO 00 sD NO CN CO in CO CO CN r^ — t ON in CO ON o 00 <7N >a- -•a- -a- CO >t CO CO CO CO % 3 j.t o 0) a 3 3 cu u o (U •-) <: CO o z Q 63 i • 8 I T C o CO > 64 number of species was encountered, but only one species, Anacystis incerta , was the dominant phytoplankter appearing at the time^ Despite these exceptions, species number has often been significantly correlated with the diversity indices (Rossmann et al« 1980). In the open lake, the diversity index normally ranges from values slightly greater than zero (in bloom situations) to values as high as 4.5 (Tarapchak and Stoermer 1976). In this system, however, the monthly mean index of the 1980 entrained samples varied from 3.58 to 4.16, with an annual mean of 3.86; in 1981, the monthly mean varied from 1.93 to 4.83, with an annual mean of 3.71. According to the Margalef (1968) classification, the ranges of values corresponding to trophic states are as follows: oligotrophic, >3.5; mesotrophic, 2.5 to 3.5; and eutrophic, <2.5. Considering the annual mean of diversity, this geographic region is still far from a state in which any disturbance drastically changes algal community structure and thereby signifi- cantly reduces the diversity index. In 1980, redundancy was low in March and high in August. In 1981, redun- dancy was low in May and high in June (Table 29, Fig. 15). When the species numbers and the diversity and redundancy indices are compared annually, the number of species is high in 1976 and 1978, but low in 1975, 1977, 1979, 1980, and 1981; the diversity index is also at its peak in 1976 and 1978; 1980 and 1981 are similar to 1975, 1977, and 1979. The redun- dancy index, however, has its maximum in 1981 and its minimum in 1976. Numbers and Biomass of Phytoplankton Passing Through the Plant — One of the major stress factors unique to entrained phytoplankton is the artificially-elevated temperature in the condenser through which entrained phytoplankton must pass. The intake water temperature during 1979 varied from 65 0^ ij OJ >s U OJ 0) 05 "5 1; £ C en O C Q. cc e ^ CO a. CO o >^ C ^ to .-- O) rs OB a a E o y-* u o o o O — • o o o — « — ' o o o 0^ O O — — o o o o o so o o 00 -3- CM -^ \0 f*^ o cs CM o m vO in o m 00 r^ ^ o ^a- _4 cn P^ m vO ON so r^ 0^ r* cr^ CM CN O o o CN o o o o O o o o o o o O O O 00 r^ p^ CN r>. o^ "^ o r^ in f^ CN o m O _4 r^ _4 CM o 00 d" CM m cn m ^ CM CN CN CN CM CN CN CM CM CN CN » CM CN CM 00 r^ cn so sO in CN a^ CN cn CM CN so CM CN CN CN CM CN CM cn CN CM cn m CM CN ^ ^ X X X X -'-s X X ^ X X CM CT\ 00 ON -^ o rm-4 NO a^ ^-4 O r^ in o o o in CM CN CN CN o o o O o o o o o o o o o m sO r^ 00 o cn o> p^ o> in ON cn to O M C&4 67 0.5°C to over 24.5°C; after the water had passed through the cooling system, its temperature at the discharge was about 10 C° higher. In the summer, the discharge water temperature approached 34 °C, the temperature suggested by- Patrick (1969) as having a harmful effect on algae. Because of possible harmful effects on algae, the numbers and biomass of phytoplankton passing through the condenser and the possible effect of this impact on phytoplankton were assessed. The plant pumped water at an average rate of 2,700 m-^ min"^ for unit #1 and 3,500 m^ min~^ for unit #2. When both units were in operation, the average rate at which water was pumped through the plant was 6,200 m-^ min""-*-. The mean monthly total phytoplankton densities were used to estimate the number of phyto- plankton passing through the plant in each month. The weight of the phytoplank- ton was then computed using the conversion coefficient of 0.57 x 10""^ gm as the average v/eight of a phytoplankton cell (Ayers and Seibel 1973). Using these methods, an estimate of the number of phytoplankton cells and their weight has been calculated for every month studied (Table 30). Not all the annual esti- mates began in January, and the units in operation were different in each year; therefore, it is not appropriate to make annual comparisons of the total en- trained phytoplankton in numbers or weight. Furthermore, the above estimates were based on the assumption that the plant was operating 100% of the time and that no recirculation of discharge water occurred. Thus, the monthly estimate represents a somewhat inflated value for the number and weight of phytoplankton passing through the plant during each month. 68 00 ON »-H •* o 00 o> -H * cr» r^ a\ ^ ^ 00 r^ ON • .^ cd ■U •> Cd r>. -^3 r-^ a> O C •K CO vO (D r^ 4J 0^ Cd ^H o •H bOXl d c •H •H U 1 T3 1 1 JJ c cd • ^ CNJ p-oo a\ 0) f-H ^ u M-4 O >s rn CO J2 'TS 4J 0) c c o •H e cd V4 OJ •u > a •H cu »+-l c 4J o CO 4J U M ^ C U-l cd rH 0) a^ o 4J u >^ TJ x: c p^ Cd • o m 0) rH ^ cd H 00 00 ON o 00 ON c •H cd u CO o> B O 00 ON ON C3N o r^ r^ r>^ 00 r^ '-H 1-H ^^ '— ♦ o o O o O — H .-H -H p— 4 -^ X X X X X * 00 r^ r-H *-4 ^H r-H --H — ^ r^ ,.1^ f-H —4 ,1.1^ — H o o o o o O O O O o o o f-4 •-H r-H ^^ »-H »-H — < »-H »-H »-H X X X X X X X X X X X X ^H 00 -^ —* ^H ^H X X X X X X X X X X X X •-H v£> v£5 CO in in ON CJN in 00 vO ON • 9 O • in • • • —4 • • CM • • • o • m ^d- -H G\ r-^ '-M ^-M r^ vO vo r^ r^ 00 00 -H f-H f-H ,-H t-H ^^ ^-H o o o o o o o XXX ON v^ f-H r^ O cN X eg X 00 in X ON o X 00 o r-H o — « X in o f—j O X en 00 .-H o X X CM ON ^ in 00 CM r^ -H ,— « CM 00 r^ r^ f^ r^ r>» r^ r^ r^ r^ r^. 00 t-H f— 4 f— 4 f— 4 f-H —^ — H ,1^ .— H F-H o o o o o o o o o o o F-H f— 4 -H ^-H F-H f— » -H f-H f— 4 f-~^ X X X X X X X X X X X ro in 00 CM ^-H in 00 CO o CM in O 00 vO 00 CM 00 <* vO r*^ 00 • • • • • • • • • • • en •-H CO in vO ^^ en * r^ 1^ r^ rv r^ r^ r^ r— 4 f-H F-H f-^ p— 4 f— 4 f^ »— H r-H F-H o o o o o O O o o o f-H f— 4 F-H ^H ^H ^H i—H i-H F^ F-H X X X X X X X X X X p^ CM cn cn CO 00 00 r^ vO F-H 00 • cn • • 00 • in • • 00 • O • m • F-H • CM F-j fO CO CM o F-H o F-H o O p>. o p^ F-H o F-H o O FiH o F-H o O o F-H F^ ^H ^-H ^-H F-H F-H ^H F-H ^H F-H f-H X X X X X X X X X X X X m C3N CM CJN in f-H r^ ON ON 00 o vO CM in CM -^r % U fQ u % 4J O 0) (]) c jQ u U >^ c rH bO P4 4J > () Cd o 00 o X vO 00 O F— 4 X in 00 00 -H o X 00 00 o f—H X -^ 00 o H 69 00 ON 00 ON o 00 ON B T3 c •r-l 4J 0^ W 60 00 ON ON T3 0) I— t U c o o en ON 00 00 00 00 00 o o o o o i-H 1-H i-H «-H <-H X X X X X o ON o 1^ en On CN ^ 00 r^ OOOOOOOOONOOOOOOONOOOOOO ooooooocoooo X X X X X X X X X X X X m 00 1— 1 f-H r-. o I-H o in O ON vO en 00 «n t-H —I CN en en I-H 1-H esj % OJ in u >^ U ^ u Q) ^ D ■u o a» (U c rO u U >% c I-H W) Ou AJ > u CO OJ CO a CO 3 :3 3 OJ u o OJ ^ fe s < S •-) *n <: en o :z Q CJN o X CJN 00 ON o I-H X o CN CJN o I-H X o CJN o f-H X o CN ON o 'x ON O f-H X en in ON o f-H X vO O 70 CHLOROPHYLLS MID PHAEOPHYTIN a The complete results of the chlorophyll a., b^, c_, and phaeophytin a^ analysis from January 1980 through May 1982 are contained in Appendix 2. These data have been used 1 ) to assess the immediate and delayed impact of entrainment on phyto- plankton viability and 2) to monitor the monthly fluctuations in these pigments with respect to the observed phytoplankton densities. Assessment of Damage to Phytoplankton Because disruption of the photosynthetic mechanism could result in the inhibition or death of the algae, analysis of the photosynthetic pigment concen- tration is used to assess viability changes associated with condenser passage. The chlorophyll molecule degrades to three pigments (phaeophytin, phaeophorbide , and chlorophyllide) . Phaeophytin (also measured in this analysis) is formed when CHLOROPHYLL -phytol ^ CHLOROPHYLLIDE -Mg -Mg \J/ PHAEOPHYTIN phytol ^ PHAEOPHORBIDE chlorophyll loses its central Mg atom. Subsequent loss of the phytol side-chain results in pheophorbide. Chlorophyllide is formed by the enzymatic removal of the phytol group from the chlorophyll molecule. Additional loss of the Mg atom produces phaeophorbide. Each of these pigments may be broken down into small colorless compounds or oxidized. Chlorophyll a^, the primary photosynthetic pigment , is found in all groups of algae and occurs in much higher concentrations than either chlorophylls b^ or c_; it is the best chlorophyll for the assessment of intake/discharge differ- ences. Chlorophylls b^ and c_, while significant for comparison with the major 71 groups of phytoplankton, do not exhibit any consequential patterns relating to entrainment. The phaeophytin a_ to chlorophyll a. ratio is relatively insensitive to changes of the magnitude that occur during entrainment, but it is also of some interest to the discussion of monthly pigment variation and seasonal suc- cession. The occurrence of statistically significant (a < 0.05) differences between pigment concentrations of intake and discharge water for all 1980, 1981, and 1982 samples are summarized in Tables 31 and 32. The differences are presented as percentages of the number of sample sets (N) for each year. There are three non-incubated and one incubated sample sets per month. As is evident from Table 31, the chlorophyll a_ concentration decreases more frequently than it increases, indicating that at least some of the pigment is altered during condenser passage. However, it is either not becoming or not remaining phaeophytin a_, because there is no apparent increase in the degra- dation product after entrainment. In fact, the data indicate that phaeophytin a^ actually decreases. It is possible 1) that the phaeophytin a^ is broken down further to phaeophorbide, 2) that the chlorophyll _a and/or the phaeophytin a_ may be degraded to small or colorless compounds, or 3) that the chlorophyll is becoming chlorophyllide . The cellular metabolism may be disrupted without any immediately detectable damage to the photosynthetic system. An assessment of delayed effects was attempted by the analysis of pigment concentration in samples 36 hours after collection. Data on the incubated samples will be dealt with in the discussion of chlorophyll a data for all study years. 72 Table 31. Percent of non-incubated sample sets which showed statistically significant (a < 0.05) differences between pigment concentrations of intake and discharge water. The number of sample sets (N) and the phaeophytin a to chlorophyll a ratio are included. Chl. a Chl. b Chl. c Phaeo a Ratio (%) (%) (%) (%) (%) Increased 1980 1981 1982 Decreased 1980 1981 1982 36 3 6 3 3 36 3 8 3 15 13 7 36 17 3 36 14 3 6 6 15 13 7 7 20 13 Table 32. Percent of incubated sample sets which showed statistically significant (a < 0.05) differences between pigment concentrations of intake and discharge water. The number of sample sets (N) and the phaeophytin a to chlorophyll a ratio are included. Chl. a Chl. b Chl. c Phaeo a Ratio (%) (%) (%) (%) (%) Increased 1980 1981 1982 Decreased 1980 1981 1982 12 8 12 17 5 20 12 8 8 8 12 25 8 25 25 25 5 73 Table 33 contains a comparison of the combined chlorophyll data for all study years. The values presented are the number of significant changes in all variables divided by the total number of comparisons for each year, and they are shown as percentages. There were 240 comparisons in 1980 and 1981, and 100 in 1982 (see Appendix 2). The difference between 1975-76 and subsequent years has been attributed to a methodology change (Rossmann et al. 1977). No consistent trends in viability are evident and only 197 7 shows a notable difference between the occurrence of increases and decreases in pigment concentrations. The mean and standard deviation (x,a) for all years are also indicated in the table. The chlorophyll a. data from Tables 31 and 32 are combined with data from previous years in Table 34. The difference between the instances of increases and decreases in the non-incubated samples of 1980-82 is consistent with earlier data. Although the years 1975, 1979, and 1982 are notable exceptions, overall, the data indicate that some decrease in viability does occur during condenser passage. Comparison of the incubated and non-incubated samples provides some information on the delayed effects of entrainment on phytoplankton viability. Delayed damage would be indicated if the percentage of incubated samples showing decreased chlorophyll a. concentration were high compared with the non-incubated samples. Only 1977 and 1981 exhibit this pattern, with the remaining data indicating that no additional viability decrease occurs within 36 hours after entrainment. Between 1978 and 1981, the somewhat higher percentage of incubated samples showing an increase (compared with non-incubated) indicates that cell division occurred during incubation and implies that the algae may have been mildly stimulated by entrainment. 74 Table 33. Percent occurrence of statistically significant changes in all comparisons between intake and discharge. Percent of Comparisons Percent of Comparisons Year Showing Increase Showing Decrease 1975 2 4 1976 4 5 1977 1 16 1978 9 9 1979 9 5 1980 3 2 1981 8 5 1982 (through May) 11 7 X = 5.9 6.6 a = 3.8 4.3 Table 34. Percent occurrence of statistically significant changes in chlorophyll a concentration between intake and discharge. Increas se Decrease Year Non- -Incubated Incubated Non- -incubated Incubated 1975 5 1976 6 8 8 1977 30 60 1978 5 17 22 17 1979 16 30 15 12 1980 3 8 17 8 1981 3 17 14 25 1982 (through May) 13 13 X = 5. 8 9. 14. 9 16.9 a = 5. 9 11. 3 8. 9 19.0 75 Although condenser passage appears to alter phytoplankton metabolism to some degree, more quantitative conclusions are hampered by our inability to sample from exactly the same "parcel" of water before and after condenser pas- sage. High variability between samples is evident in the chlorophyll data, as well as the species counts, and may be due in part to the "patchiness" of the phytoplankton in the lake. Furthermore, chlorophyll analysis, while providing an indication of the phytoplankton 's gross condition (dead or alive), is not sensitive enough to subtle changes in viability of the degree likely to occur during entrainment. Primary productivity data based on uptake of C-14 indicate that a reduction in the photosynthetic rate occurs even though little signifi- cant change in chlorophyll a_ is observed (Chang et_ _ai . i93ib). Factors causing the rate reduction and details concerning the duration of the change are still unclear. Monthly Variation of the Chlorophylls and Phaeophytin a Data from the intake samples are used to monitor monthly chlorophyll and phaeophytin a. fluctuations. The results for January 1980 through May 1982 are illustrated in the figures which follow. Comparison of these with the major group plots (Figs. 3-12) gives an indication of the origins of chlorophyll peaks. Chlorophyll a. (Fig. 16) is present in all major groups of algae and the monthly levels are associated closely with the seasonal succession of phyto- plankton (Total Algae, Fig. 12). All years show regular spring and fall peaks. Spring chlorophyll a peaks resulted primarily from the high abundance of dia- toms, while the fall increases were caused by greens, coccoid blue-greens, and diatoms. 76 -■ i ■•I ^ 9 Ql S it; -.55 T i ••I u. i *• ^ »{ t ^ O Z 00 i i "•? orsi vzi org 00*9 d3I3U 3X803 dad SUbdOnilU 00 as 13 C cd 30 ON o 00 bO c 3 T3 03 c o CO u C 0) o c o o eO| a o o iH c o CO > o M 77 Chlorophyll b^ (Fig. 17) is found primarily in green algae. In addition to the coccoid and filamentous groups, flagellates and especially Other Algae may contain sizable green algae components. The green species of flagellates made a major contribution to the April 1980 chlorophyll _b peak; and the greens in Other Algae, along with the coccoid greens, were the important constituents of the Fall 1980 increase. A single species of filamentous green algae appears respon- sible for the chlorophyll h peak in May 1981. The original phytoplankton counts for that month (see Appendix 1) indicate a high abundance of Ulothrix sp. in one of the samples. The large peak in January 1982 must be attributed to experi- mental error, because no group of algae occurred in numbers sufficient to produce such an increase. Pennate and centric diatoms are the principal contributors of chlorophyll c in the phytoplankton samples, and the chlorophyll £ plot (Fig. 18) follows the seasonal succession of diatoms. Chrysophycean flagellates, dinof lagellates , and cryptomonads (lumped into the major group Flagellates) also contain the pigment; but their combined biomass is considerably less than that of the diatom fraction. The phaeophytin a. levels (Fig. 19) generally follow the pattern seen in chlorophyll a^, although the actual concentration of phaeophytin remains well below that of chlorophyll. The peak in May 1981 is larger than usual but is in line with the high abundance of phytoplankton observed for that month. The ratio of phaeophytin a^ to chlorophyll a. (Fig. 20) was high in April 1980, prior to the spring phytoplankton bloom. This increase may have resulted from the spring turnover, when decaying algae are brought up from the bottom. The ratio remained relatively low through the rest of 1980 and early 1981. In May 1981, the ratio increased sharply, possibly again as the result of turnover. 78 X Q. O cr o OrO 91-0 21-0 bSiiu oiano aad sudaoiniu CM 00 ON c CO 00 ON o 00 ON bO c •H 3 CO C o cd u c O c o o •^1 a o u o iH u a o •H U Cd CO > M PB4 79 " 2 8 CD I S I I i 00 ON CO 00 ON o 00 c CO C o u u c a c o o a o u o iH a o Cd > 00 c o M K'f ore o»T ot'i K'l d3i3U 31803 H36 SUbdOiniU 80 SL't ^ 9trt srz os*i a3i3u Diana d3d subdoiniu eg cd 30 o 00 as bO •H U 3 CO C o CO C 0} a c o o 4J o ON M CS4 81 00 OS Ql o O 5 I UJ d X a. T3 C CO 00 ON o 00 u 4J CO u a o u o a o CO a o CO > o Csl O 82 The points from June through September are difficult to interpret, but the gradual rise in the ratio from October 1981 through January 1982 was probably the result of the decline of the winter bloom. 83 SUMMARY In 1980, orthophosphate concentration ranged from O^ll ppb during maximum utilization in June to 1.25 ppb in October, after the onset of fall turnover. Nitrate varied from 0.143 ppm (September) to 0.5 ppm (April), and nitrite was detectable in January, April, and June. Dissolved silica concentrations ranged from 1.36 ppm during the spring turnover in April down to 0.06 ppm after the winter bloom. For 1981, orthophosphate was at its minimum level of 0.215 ppb during the diatom bloom in November and at its maximum of 1.83 ppb, atypically, in Decem- ber. Nitrate ranged from 0.11 ppm in June to 0.481 in December; and nitrite was present in April, July, August, October, November, and December. Dissolved silica varied from 0.409 ppm in August, well after the May diatom bloom, to 2.22 ppm in March, perhaps as a result of runoff combined with the beginning of turnover. It exceeded 1.0 ppm in January (1.18), February (1.53), March (2,22), October (1.42), November (1.02), and December (1.68). In the 1982 samples available, orthophosphate generally decreased between the maximum in January (0.979 ppb) and the minimum in May (0.0409 ppb). Nitrite appeared in April, with spring turnover. Spring maximums for dissolved silica (1.2 ppm) and nitrate (0.453 ppm) also occurred in April. Utilization was evident in May, when the dissolved silica concentration was 0.314 ppm and the nitrate concentration was 0.0303 ppm. Coccoid blue-green algae were low in concentration during February through May and high in concentration from July through December 1980. In 1981, concen- trations were low from January through July and high in September, with a decrease from October through December. Concentrations were low in 1982 from 84 January through May. Filamentous blue-green algae were less numerous than coccoid blue-green algae and peaked in June 1980 and May 1981, with 312 cells/mL and 111 cells/mL, respectively. Coccoid green algae were relatively high during July through September 1980 and July 1981. Filamentous green algae reached 9 cells/mL in May 1980 and 85 cells/mL in May 1981, thus constituting a minor portion of the total algal population. Flagellates were numerous and contrib- uted an important share to the total annual algal population. They peaked in April 1980 and were low during October through December 1980. In 1981, flagel- lates peaked in June and were considerably higher than 1980 for the remainder of the year. The yearly means for 1981 and 1982 were the highest for 1975-1982. Centric diatoms peaked in May and September 1980; May, September, and November 1981; and April 1982. Pennate diatoms were most abundant in May and November 1980; May and December 1981; and April and May 1982. Desmids were consistently low during 1980-1982, reaching 5 cells/mL in May 1981. Other algae had peak abundances in September 1980, and April and September 1981. Total algae numbers were highest in May, September, October, and November 1980; May, September, and November 1981; and April 1982. Comparison of phytoplankton major group mean concentrations for 1975 to May 1982 gave the following general observations: 1) coccoid blue-green algae and desmids were least abundant during 1976; 2) coccoid green algae and centric diatoms were least abundant in 1977; 3) flagellates were least abundant in 1979-1980; 4) filamentous blue-greens were least abundant in 1981; 5) filamen- tous green algae were most abundant in 1976, and other algae were most abundant in 1981; 6) total algae and pennates were least abundant in 1979. The reason for this low count in 1979 may be the absence of June samples, when the 85 abundance is usually high. The value for the yearly average may, therefore, be unduly low. The number of forms of phytoplankton identified during 1980 varied from 41 in July to 70 in September, In 1981, forms varied from 40 in July to 65 in September, Diversity ranged from 3,58 in August to 4.16 in June during 1980, and from 1.93 in June to 4.83 in May 1981; and redundancy varied from 0.240 in March to 0.396 in August 1980, and from 0.197 in May to 0.661 in June during 1981. The average number of forms and the redundancy index were highest in 1976 and 1981, respectively; and diversity was highest in 1976 and lowest in 1981. Important trends have been observed in entrainment assemblages: 1) a con- tinuous frequent occurrence and large abundance of the blue-green alga Anacystis incerta through 1980, followed by a substantial decrease in 1981; 2) decline in the occurrence of Gomphosphaeria lacustris in 1980-1981; 3) a large increase in the occurrence of flagellates and chrysophycean flagellates through 1981; and 4) a continued increase in the occurrence of dominant blue-green algae through 1979, and then a sharp decline in 1981. A combination of decreasing occurrences of mesotrophic species that are intolerant of nutrient enrichment and of higher occurrences of eutrophic and mesotrophic species tolerant of moderate nutrient enrichment illustrates the continuing degradation of this southern sector of Lake Michigan. Viability results based on the comparisons of chlorophyll and phaeophytin concentrations of intake and discharge samples were variable and lacked consis- tent trends in the years (1975-1982) under consideration. Only 1977 showed a significant decrease in viability after condenser passage, with 16% of the sampling periods exhibiting lower chlorophyll levels and only 1% having higher 86 levels after entrainment . However, comparison of chlorophyll a concentrations before and after condenser passage shows a lower concentration for all study years except 1979, indicating that some damage does occur. Chlorophyll £ levels in the incubated samples imply a delayed stimulatory effect on viability but are inconclusive because of the high variability of the samples. 87 LITERATURE CITED Ayers, J. C. 1975a. Benton Harbor Power Plant Limnological Studies. Part XXI. Bacteria and phytoplankton of the seasonal surveys of 1972 and 1973. Univ. Michigan, Great Lakes Res. Div. , Spec. Rep. No. 44, 152 pp. Ayers, J. C. 1975b. The phytoplankton of the Cook Plant monthly minimal surveys during the preoperational years 1972, 1973, and 1974. Univ. Michigan, Great Lakes Res. Div. , Spec. Rep. No. 59, 51 pp. Ayers, J. C. 1978. Benton Harbor Power Plant Limnological Studies. Part XXV. Phytoplankton of the seasonal surveys of 1976, of September 1970, and pre- vs. post-operational comparisons at Cook Nuclear Plant. Univ. Michigan, Great Lakes Res. Div., Spec. Rep. No. 44, 258 pp. Ayers, J. C. , and L. E. Feldt. 1982. Benton Harbor Power Plant Limnological Studies. Part XXIX. Phytoplankton of the seasonal surveys of 1978 and 1979, and further pre- vs. post-operational comparisons at Cook Nuclear Plant. Univ. Michigan, Great Lakes Res. Div., Spec. Rep. No. 44, 7U pp. Ayers, J. C. , and L. E. Feldt. 1983. Benton Harbor Power Plant Limnological Studies. Part XXXI. Phytoplankton of the seasonal surveys of 1980, 1981, and April 1982, and further pre- vs. post-operational comparisons at Cook Nuclear Plant. Univ. Michigan, Great Lakes Res. Div., Spec. Rep. No. 44, 91 pp. Ayers, J. C. , and E. E. Kopczynska. 1974. The phytoplankton of 1973, pp. 139-174. In The biological, chemical and physical character of Lake Michigan in the vicinity of the Donald C. Cook Nuclear Plant. E. Seibel and J. C. Ayers, eds. Univ. of Michigan, Great Lakes Res. Div., Spec. Rep. 51. 88 Ayers, J. C. , and E. Seibel, 1973. Benton Harbor Power Plant Limno logical Studies. Part XIII. Cook Plant preoperational studies, 1972. Univ. Michigan, Great Lakes Res. Div. , Spec. Rep. No. 44, 281 pp. Ayers, J. C. , and S. J. Wiley. 1979. Benton Harbor Power Plant Limno logical Studies. Part XXVII. Phytoplankton of the seasonal surveys of 1977, and further pre- vs. post-operational comparisons at Cook Nuclear Plant. Univ. of Michigan, Great Lakes Res. Div., Spec. Rep. No. 44, 92 pp. Ayers, J. C. , R. F. Anderson, N. W. O'Hara, and C. C. Kidd. 1970. Benton Har- bor Power Plant Limnological Studies. Part IV. Cook Plant preoperational studies 1969. Univ. Michigan, Great Lakes Res. Div., Spec. Rep. No. 44, 92 pp. Ayers, J. C. , D. E. Arnold, and R. F. Anderson. 1971. Benton Harbor Power Plant Limnological Studies. Part VII. Cook Plant preoperational studies 1970. Univ. Michigan, Great Lakes Res. Div., Spec. Rep. No. 44, 85 pp. Ayers, J. C, H. K. Soo, and W. L. Yocum. 1972. Benton Harbor Power Plant Limnological Studies. Part X. Cook Plant preoperational studies, 1971. Univ. Michigan, Great Lakes Res. Div., Spec. Rep. No. 44, 152 pp. Ayers, J. C. , S. C. Mozley, and J. A. Stewart. 1974. Benton Harbor Power Plant Limnological Studies. Part XIX. The seasonal biological surveys of 1971. Univ. Michigan, Great Lakes Res. Div., Spec. Rep. No. 44, 181 pp. Ayers, J. C. , N. V. Southwick, and D. G. Robinson. 1977. Benton Harbor Power Plant Limnological Studies. Part XXIII. Phytoplankton of the seasonal surveys of 1974 and 1975 and initial pre- vs. post-operational comparisons at Cook Nuclear Plant. Univ. of Michigan, Great Lakes Res. Div., Spec. Rep. No. 44, 279 pp. 89 Chang, W. , R. Rossraann, J. Pappas , and W. L. Yocum. 1981a. Benton Harbor Power Plant Limnological Studies. Part XXVIII. Entrainment of phyto- plankton at the Donald C. Cook Nuclear Plant-1978. Univ. of Michigan, Great Lakes Res. Div. , Spec. Rep. No. 44, 106 pp. Chang, W. Y. B. , W. Yocum, and J. Barres. 1981b. Response of phytoplankton to power plant entrainment. Abstracts of the Twenty-fourth Conference on Great Lakes Research, International Association for Great Lakes Research, p. 36. Holland, R. E. 1968. Correlation of Melosira species with trophic condi- tions in Lake Michigan. Liranol. Oceanogr. 13: 555-557. Holland, R. E. 1969. Seasonal fluctuation of Lake Michigan diatoms. Limnol. Oceanogr. 14: 423-436. Holland, R. E. , and A. M. Beeton. 1972. Significance to eutrophication of spatial differences in nutrients and diatoms in Lake Michigan. Limnol. Oceanogr. 17: 88-96. Margalef. 1968. Perspectives in Ecological Theory. University of Chicago Press, Chicago, Illinois, 111 pp. Moss, B. 1973. Diversity in fresh-water phytoplankton. Amer. Mid. Natur. 90: 341-355. Patrick, R. 1969. Some effects of temperature on freshwater algae, pp. 161-185. In Krenkel and Parker (eds.). Biological Aspects of Thermal Pollution. Vanderbilt Univ. Press. 90 Rossmann, R. , N. M. Miller, and D. G. Robinson* 1977. Benton Harbor Power Plant Limnological Studies. Part XXIV. Entrainment of phytoplankton at the Donald C. Cook Nuclear Plant 1975. Univ. of Michigan, Great Lakes Res. Div. , Spec. Rep. No. 44, 264 pp. Rossmann, R. , L. D. Damaske, and N. M. Miller. 1979. Benton Harbor Power Plant Limnological Studies. Part XXVI. Entrainment of phytoplankton at the Donald C. Cook Nuclear Plant - 1976. Univ. of Michigan, Great Lakes Res. Div., Spec. Rep. No. 44, 88 pp. Rossmann, R. , W. Chang, L. D. Damaske, and W. L. Yocum. 1980. Entrainment of phytoplankton at the Donald C. Cook Nuclear Plant - 1978. Univ. of Michigan, Great Lakes Res. Div., Spec. Rep. No. 67, 180 pp. Rossmann, R. , W. Chang, and J. Barres. 1982. Benton Harbor Power Plant Lim- nological Studies. Part XXX. Entrainment of phytoplankton at the Donald C. Cook Nuclear Plant - 1979. Univ. of Michigan, Great Lakes Res. Div. , Spec. Rep. No. 44, 98 pp. Sanford, G. R. , A. Sands, and C. R. Goldman. 1969. A settle-freeze method for concentrating phytoplankton in quantitative studies. Limnol. Oceanogr. 14: 790-794. Stoermer, E. F. , and J. J. Yang. 1969. Plankton diatom assemblages in Lake Michigan. Univ. of Michigan, Great Lakes Res. Div., Spec. Rep. No. 47, 268 pp. Stoermer, E. F. , and J. J. Yang. 1970. Distribution and relative abundance of dominant plankton diatoms in Lake Michigan. Univ. of Michigan, Great Lakes Res. Div., Publ. No. 16, 64 pp. 91 Strickland, J. D. H. , and T. R. Parsons. 1972. A Practical Handbook of Seawater Analysis. 2nd ed. Fish. Res. Board Can. Bull. #167. 310 pp, Tarapchak, S. J., and E. F. Stoeriner. 1976. Environmental status of the Lake Michigan region. Vol. 14. Phytoplankton of Lake Michigan. Argonne National Laboratory. 211 pp. Wilhm, J. L., and T. C. Dorris. 1968. Biological parameters for water quality criteria. Bioscience 18: 477-481. 92