BENTON HARBOR POWER PLANT LIMNOLOGICAL STUDIES PART XXVII. PHYTOPLANKTON OF THE SEASONAL SURVEYS OF 1977, AND FURTHER PRE- vs. POST-OPERATIONAL COMPARISONS AT COOK NUCLEAR PLANT John C. Ayers Susan J. Wiley Under Contract with: American Electric Power Service Corporation Indiana & Michigan Electric Company Special Report No. 44 of the Great Lakes Research Division The University of Michigan Ann Arbor, Michigan March 1979 PREVIOUS PARTS OF THE REPORT SERIES RELATIVE TO THE DONALD C. COOK NUCLEAR STATION Benton Harbor Power Plant Limnological Studies 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. ^5 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. 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. iii PREVIOUS REPORTS continued 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. I8l 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. Entrainraent 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 comparisons 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.). Seibel, 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. IV PREVIOUS REPORTS continued 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 southeastern 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. I87 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. 1978. The 1975 and 1976 operational zooplankton investigations relative to the Donald C. Cook Nuclear Power Plant with preoperational tests (1971-1976) for plant effects. Special Report No. 64 of the Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan. 166 pp. Plus appendix of 4 microfiche cards. TABLE OF CONTENTS Page PREVIOUS PARTS OF THE REPORT SERIES RELATIVE TO THE DONALD C. COOK NUCLEAR PLANT iii FIGURES viii TABLES ix ACKNOWLEDGMENTS x INTRODUCTION 1 TECHNIQUES 5 RESULTS AND DISCUSSIONS 8 The Thermal Bar of 14 April 1977 8 Phytoplankton Summary Tables 12 Dominant and Codominant Phytoplankters 12 Master Lists of Phytoplankters Collected 25 Continued Increase of a New Diatom Species 26 Major Algal Group Percentages at Plant and Reference Stations, 1970-1977 27 Inner-Outer Graphical Comparisons: Numbers of Forms 30 Inner-Outer Graphical Comparisons: Diversity Indices 37 Inner-Outer Graphical Comparisons: Phytoplankton Redundancies . 42 Inner-Outer Graphical Comparisons: Phytoplankton Abundances by Algal Categories 45 Inner-Outer Statistical Comparisons: Phytoplankton Abundances by Algal Categories, 1970-1977 68 CONCLUSIONS 86 REFERENCES 91 Appendices are in microform inside back cover APPENDIX A: PHYSICAL MEASUREMENTS 93 APPENDIX B: PHYTOPLANKTON COLLECTIONS 98 APPENDIX C: MASTER LISTS OF PHYTOPLANKTON COLLECTED 209 vii LIST OF FIGURES Figure Page 1 . The Cook Plant 36-station sampling grid used for phytoplankton after April 1972 3 2. The thermal bar and phytoplankton abundances in the Cook Plant grid on 14 April 1977 10 3. Histograms of phytoplankton, sulphate, and chloride during the thermal bar condition of 14 April 1977. . . 11 4. Major group percentage compositions of the phytoplankton, July 1970 through November 1977 .... 28 5. Mean numbers of phytoplankton forms collected in three depth zones and in inner-outer* station groups, preoperational 1970-1974 and operational 1975-1977 33 6. Mean diversity indices of phytoplankton collections in three depth zones and in inner-outer station groups, preoperational 1970-1974 and operational 1975-1977 . . 39 7. Mean redundancies of phytoplankton collections in three depth zones and in inner-outer station groups, preoperational 1970-1974 and operational 1975-1977 . . 46 8. Mean abundances of ten categories of phytoplankton in three depth zones and in inner-outer station groups, preoperational 1970-1974 and operational 1975-1977 8A (Desmids) 51 8B (Filamentous greens) 52 8C (Other algae) 53 8D (Filamentous blue-greens) 54 8E (Coccoid blue-greens) 55 8F (Coccoid greens) 57 8G (Flagellates) 58 8H (Pennate diatoms) 59 8l (Centric diatoms) 51 8J ( " " ) 62 8K ( " " ) 63 8L (Total algae) 64 8M ( " " ) 65 8N ( " " ) 66 Vlll LIST OF TABLES Table Page 1 . Comparison of the original 54-station sampling grid to the 36-station grid used after April 1972 4 2. Phytoplankton summary tables, 1977 ... 13 3. Dominant and codominant phytoplankters in the Cook Plant seasonal surveys, preoperational 1970-1974 and operational 1975-1977 18 4. Means, standard errors, and numbers of observations of phytoplankton forms by seasons, depth zones, and inner-outer station groups in Cook Plant seasonal surveys during 1977 32 5 . Means , standard errors , and numbers of observations of phytoplankton diversity indices by seasons, depth zones, and inner-outer station groups in Cook Plant seasonal surveys during 1977 38 6. Means, standard errors, and numbers of observations of phytoplankton redundancies by seasons, depth zones, and inner-outer station groups in Cook Plant seasonal surveys during 1977 44 7. Means, standard errors, and numbers of observations of abundances of ten categories of phytoplankton by seasons, depth zones, and inner-outer station groups in Cook Plant seasonal surveys during 1977. . . 48 8. Statistical tests of mean abundances of ten categories of phytoplankton at inner vs. outer station groups by seasons and depth zones in Cook Plant seasonal surveys 1970 through 1977 71 IX ACKNOWLEDGMENTS We are indebted to a number of persons for their contributions to the completion of this study. Field assistance has been rendered by members of the fisheries, benthos, and zooplankton sections to whom our thanks are extended. The captain and crew of the R/V MYSIS have provided much appreciated field assistance over and above their mere duty. Pairoj Waiquamdee is thanked for drafting and computer work well done. To members of the phytoplankton staff who carried out the tedious but essential work of counting and identifying phytoplankton samples we extend our sincere gratitude; they were Nancy Southwick Rago, Sally Kleinschmidt , and Douglas Hodgkins. One of us (SJW) also participated in this work. Gregory Godun is thanked for assistance and advice in statistical matters. INTRODUCTION The Donald C. Cook Nuclear Plant is located on the southeastern shore of Lake Michigan, in Lake Township, Berrien County, Michigan. The plant is approximately 1 1 miles south of Benton Harbor and two miles north and west of Bridgman , Michigan . A 2-unit electric generating station, the plant is rated at 2200 megawatts and draws cooling and service water from Lake Michigan through three intake pipes from approximately 2250 feet offshore in 24 feet of water. The plant employs a once-through cooling system, returning used cooling water to the lake through two diffuser discharge structures located approximately 1200 feet offshore in 18 feet of water. Unit 1 began operating in January 1975 and unit 2 in early 197S. With both units at full power the condenser cooling water flow rate is 1,645,000 gpm 9 (3650 cfs) and the total heat rejection rate is 15.5 x 10 Btu per hour. Unit 1 at full power inparts to the condenser cooling water a temperature rise of 21.8 F ; unit 2 at full power produces a rise of 16.7 F in its cooling water. Used cooling water from unit 1 returns to the lake through a 2-slot diffuser discharge structure; that from unit 2 through a 3-slot diffuser discharge structure. The exit velocities at both diff users are about 13 ft/sec. The discharge velocities create an area of high turbulence in front of each discharge structure. The regions of high turbulence are short-lived both temporally and spatially as ambient water is rapidly entrained into the discharged water and the velocity of the discharged water falls quickly to ambient current velocity. Phytoplankters drawn into the plant with cooling water are subject to sudden increase in temperature, mauling by pumps, chlorination of cooling water, high velocity discharge, and rapid dilution with cooler water. Operation of the plant, then, has at least the potential of affecting the structure of the phytoplankton community. The strategy for detecting changes in the phytoplankton community near the Cook Plant involves comparisons of phytoplankton abundances in three depth zones near the plant to abundances in the same three depth zones at distances two miles or more away from the plant. In any one survey these comparisons are spatial but, repeated over time, they allow temporal comparisons as well. The temporal comparisons primarily consist of conditions in preoperational years compared against operational years. Conditions in preoperational years provide a measure of natural variation against which variations in operational years may be compared to detect possible plant-related perturbations. This report serves the double purpose of recording the results of seasonal surveys carried out in 1977 and of presenting additional preoperational vs postoperational analyses according to the strategy outlined above. Figure 1 shows the station positions of the present 36-station sampling grid centered on the Cook Plant. This grid, used after April 1972, replaced an earlier 54-station grid. Table 1 compares the two sampling grids and shows the stations dropped and stations retained in changing to the 36-station grid. At all complete stations in Figure 1 phytoplankton, zooplankton, benthos, and physical measurements are collected during the seasonal surveys. The physical measurements consist of surface-water temperature, water depth, bottom type, Secchi disc water transparency, and water color as seen above the white 20-cm Secchi disc, as well as weather conditions and wind and wave characteristics. The seasonal physical data are given in Appendix A. Occasionally weather or logistical difficulties result in some stations of a survey being taken a day ahead of or a day later than the bulk of the stations. This results in different dates on the phytoplankton station s ^ • c ^ O/^ /A n. CM Cd Cd ^ 7 , q> o ^4 I ^ ^ J3 ^ 0} O o u r-^ , 0) 4J OQ (U r-f rH Cd i: -D cd o a CO A O C C >» x: c c CD c -C E-» O O £ cd fH OB a. -H -H H rH cd 2 <3 • cd Cd SL. .- , , »- 4J 4-> • (D CD si I III . " "-SS " M x: Q rH » •H rH £i Q) Cm O T3 a; O c 4J T3 •H 03 Sm C OJ CO •H 5 (D •o T3 •H C C ^ •H 03 iH H CO DO c iH t. a> -c Sm 4-) OJ 03 c ja 3 o 4J iH Sh ^ 03 Q) c S B m t. J« (— 1 03 c-^ 5 o ^ -fcj T} >^ (D C sz x: 03 C H ? <;-♦ Zi* o • 03 c- 3 c ^- o ON Vj •H t— 03 4J iH ^ rH ^ H o •H U 4J t. a 4-i '•a: :^ 00 0) •H .=r ^ -o '^ § 0) Cm x: O t- H c -o o rH • •H O C\J 4J H o e •a J= o c ^ M o •H Ct. o 3 10 6000 CELLS. 400CI 200C 14 APRIL 1977 3 i t I 3 3 2 3 4 5 6 7 8 9 10 H 12 'C 6 II I 20 . 1 » PPM -n.-— - ' r SO4 15 ■ 10 5 < 3 1 1 \ 3 3 6 II 1 ) 1 ; 5 - \ 5 ( B 7 1 8 S ) 1 11 i 15 PPM or 10 I I I 3 6 II I 2 3 45 67 89 ran 12 'C FIG. 3. Histograms of phytoplankton densities (cells/ml) and of sulphate and chloride by one C°water temperature intervals during the thermal bar condition of 14 April 1977. Numbers within the bars indicate the numbers of samples averaged. 11 PhvtoDlankton Summary Tables The phytoplankton summary tables employed here are based on the ones used by the Michigan Water Resources Commission at the time our reporting procedures were established (MWRC, 1970). Our summaries differ from theirs in that we count the numbers of cells in filamentous and colonial forms (except blue-green algae with cylindrical trichomes which are counted as individual organisms), while the Commission counts a filament or colony as a single organism. The station collection records from which the summaries for 1977 were prepared constitute Appendix B. The summary table for each seasonal survey presents, station-by-station, the surface-water temperature at the time of collection, the numbers per ml of each of ten major categories of planktonic algae, and the dominant (and codominant, see below) species or groups. The categories of phytoplankton employed are: coccoid blue-green algae, filamentous blue-green algae, coccoid green algae, filamentous green algae, flagellates, centric diatoms, pennate diatoms, desmids, other algae, and total algae. The summary tables allow quick assessment of the general compositions of the populations sampled, the ambient water temperature, and give the dominant and codominant species or groups (forms). The summary tables presented in Table 2 cover the surveys of spring (April), summer (July), and fall (October) of 1977. Dominant and Codominant Phvtoplankters In each phytoplankton sample one form (species or group) is typically present in greater abundance than the others. We designate these species or groups as "dominant." 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On the whole, the temporal changes of the component parts of the phytoplankton communities at the two station groups have been qualitatively similar in the preoperational years; only in the flagellates and green algae in 1973 were the changes directionally different in the two station sets. In the operational years the compositional changes in the communities at the plant and reference stations have been, if anything, even more similar than in the preoperational period. In both the plant and the reference stations in 1975 flagellates represented a greater proportion of the population than in 197^, though not so great a one as was observed in September-November 1970 and about the same as in July 1972. As a result of the warmer summer, flagellates in both station groups reached their greater abundances a month earlier than in 1974, Green algae in both plant and reference stations began their greater abundances in July 1975, again an effect of the warmer summer. In neither station group did these algae reach the massive proportions of the populations that were observed in 1971. In 1976 the partitionings of the five components of the phytoplankton populations were, in both the plant stations and the reference stations, different from those observed in previous years. Blue-green and green algae did not exhibit the pronounced maxima or minima of other years. Flagellates in both station groups were generally a higher and more sustained proportion of the population than in other years. Desmids and other algae peaked in September, which had not been seen before. The summer diatom minimum occurred in June in the plant stations and in June and July in the reference stations; in both sets of stations the minima were less severe than in 1974 29 or 1975. In general, it appears that in 1976 flagellates and desmids and other algae increased at the expense of diatoms , coccoid and filamentous greens, and blue-green algae in both the plant and the reference stations. In 1977 blue-greens returned to the summer peak levels of 1974 and 1975. Green algae, in both sets of stations, were a minor part of the population in each of the surveys. Flagellates were, somewhat more abundant in spring 1977 than in the springs of preceeding years and had a May peak in abundance at the expense of the diatoms . Diatom summer minima occurred in August in each station set; a second minimum occurred in October at the plant stations and in November in the reference stations. Desmids and other algae peaked in September as they had in 1976. Except that the fall increase in diatoms and decrease in blue-greens had begun in November at the plant stations but not yet at the reference stations, the abundance changes in the two sets of stations were directionally similar in 1977. No dissimilarities attributable to plant operation have been revealed by this method of analysis. Inner-Outer Graphical Comparisons: Numbers of Forms In this section the term "forms" includes organisms identified to species (e.g. Melosira jg;ranulata ) y organisms identified only to genus (e.g. Ulothrix sp. or spp.), and composite groups of unidentified organisms (e.g. Flagellates) . Data on the numbers of phytoplanktonic forms in collections from the Cook Plant region in the years 1971 through 1975 have been presented and discussed by Ayers, Southwick, and Robinson (1977); Ayers (1973) extended the data and discussions to include 1970 and 1976; for the most part the tabulated data in those reports are not repeated here. This section concerns 30 itself with extending the previous tabulations, figures, and discussions to include the seasonal surveys of 1977. Numbers of forms are listed in each station collection in Appendix B. As was done in the reports cited, the data on numbers of forms present in 1977 are stratified by three depth zones and inner (treatment) and outer (control) station groups. Stations along, or less than two miles north or south of, a central transect extending perpendicular to shore from the Cook Plant are defined as inner stations which might be affected by plant operation. Stations 2 miles or more north or south of the plant are defined as north and south reference stations or, lumped together, as outer stations. Zero to 8 m depths are designated "Zone 0"; 8 to 16 m as "Zone 1"; and 16 to 24 m as "Zone 2." For each depth zone there are inner and outer station groups. The depth zones and station groups used are: Depth Zone Depth Range Inner Station Group Outer Station Group to 8 m DC-0 NDC-2-0 DC-1 NDC-2-1 NDC-.5-0 NDC-4-0 NDC-.5-1 NDC-4-1 NDC-.5-2 NDC-7-1 NDC-1-0 SDC-2-0 NDC-1-1 SDC-2-1 SDC-.5-0 SDC-4-0 SDC-.5-1 SDC-4-1 SDC-.5-2 SDC-7-1 SDC-1-0 SDC-1-1 8 to 16 m DC-2 NDC-2-3 NDC-1-2 NDC-7-3 SDC-1-2 SDC-2-3 SDC-7-3 16 to 24 m DC-3 NDC-4-3 DC-4 NDC-7-5 SDC-4-3 SDC-7-5 Mean numbers of forms, the associated standard errors, and numbers of 31 observations have been computed and are given in Table 4. TABLE 4. Means, standard errors, and numbers of observations of phytoplankton forms by seasons, depth zones, and inner and outer station groups in Cook Plant seasonal surveys 1977. Previous years are reported by Ayers, Southwick, and Robinson (1977) and Ayers (1978). 1977 14 April HJulx 14 October 57.33 66,50 4.86 3.91 Zone 0, Inner Mean S. E. M 57.17 2.74 12 Outer Mean S. E. N 51.60 1.63 10 Zone 1 , Inner Mean S. E. N 57.67 9.17 3 Outer Mean S. E. N 54.00 6.37 4 Zone 2, Inner Mean S. E. N 61.00 4.00 2 Outer Mean S. E. N 46.75 5.44 4 12 12 54.00 63.10 6.78 4.84 9 10 42.67 68.00 5.33 6.43 3 3 48.25 71.25 3.04 9.76 4 4 42.00 61.50 2.00 0.50 2 2 40.50 45.50 1.33 2.85 4 4 Time plots of mean numbers of forms by seasons , depth zones , and inner and outer station groups are presented in Figure 5. Also included in the figure are, for each year, three-seasonal averages of mean numbers of forms at inner and outer stations; these are plotted in July of each year and are connected 32 00 q: O Li. Ll O en [±1 CD o u z O o ^ Q: .^ "1 u ^_ 18 uO (jO z z < < U UJ 2 2 ^' -J < < z z O O 00 (jO < < ijj LU LH Ul Ul Ll. O o UJ LJ o o < < q: q: LU LU > > < < z z O O uo (y") Q: cc < < LU u UJ LU z 1 — UO C/) z -J O m m < r 9 1^ ^ b 6 <:[i> o ( 3 Oi 00 o ^. — ) < ^ CD CD LO < ^ O) < ^ P CM O < — z O uO O) o • -P CO 3 C O •H C CO m > SL. 0) (D CO G ^ G O •H » rH jC CO cx o •H <<-♦ 4J O £. 0) W > u S H c c CO LO CQ a 3 O su c o o o LP; c o o J O a CO 33 or O IJL u. O q: u CD Z) z LlI z o < ^ O CD < ^ O ID 0^ o en o < ^ O 04 O (v uO O) a; O o o o o CO o o o o o en C CM O CO Ci- CQ 34 Z o Ll Ll o q: u CD Z) C\J UJ z: O INI O o Q: c: UJ LjJ Z h- . Z =5 - O (yi (/) z z < < LU UJ Z 2 -j -J < < z z O O m ld < < U UJ in 00 U- Li_ O O UJ UJ CD CD < < q: cc UJ UJ > > < < z z O GC q: to ^ U UJ < < z ^ U UJ z -^ 00 (/) O c^ ^ 1 4 ^ 53 C? ^ A i Q o CT) 00 O IV IV < ^ O CD IN O o in IN o IN K '- o en !N G) o < — m IN o IN o o o O o O CO o o -o ^ C ctJ 03 > SU ^M 0) CD CO C JD C O •H C O •H QQ 3 -o C c Cd u o u Q) ^ S S 0) 3 rH CO jQ Cd *H C

> rH ^ Cd cu o ^ 4^ C t- 0) CO > xi x: E H C c Cd o CO a O bO C o a Cd M 4-i Ct4 CO 35 from year to year by a solid line for inner stations and a dashed line for outer stations. Such averages for 1970 are not given because only summer and fall were surveyed . The three-seasonal averages of numbers of forms in 1977 are: Zone 0, inner 60.3, outer 56.2; Zone 1, inner 56.1, outer 57.8; Zone 2, inner 54.8, outer 44.3. Ayers (1978) gives the values for 1971 through 1976. The annual curves of mean numbers of forms in Figure 5 show substantial degrees of parallelism, indicating that the numbers of forms in inner and outer station groups have in general varied in the same directions from season to season in each year. In Zone the positions of the annual curves on the graphs and the three-seasonal averages indicate steadily rising tendencies from 1971 through 1976 with a small decrease in 1977. In Zone 1 the curve positions and averages show a tendency to plateau in 1973 through 1975 with increases in 1976 and 1977. In Zone 2 the curve positions and averages for the outer stations show a slow increase in numbers of forms; the inner stations of this zone well off shore show an overall tendency for increase and for there to be more forms at these stations than at the outer ones, conditions which have been true since 1971. The tendency for increase in numbers of phytoplankton forms in Cook Plant collections since 1971 is consistent with the observations of Stoermer and Yang (1969, pp. 209 and 211) that phytoplankters have been introduced into Lake Michigan in recent decades and that one of the effects of nutrient enrichment from man's activities has been to make the planktonic environment more accessible to forms that find their primary habitat in benthic assemblages. There is no convincing evidence from this analysis that operation of the Cook Plant since 1975 has had any effect on the local phytoplankton community, 36 instead the increases in form numbers at the inner and outer station groups appear to be an effect of the lake's eutrophication process. Inner-Outer Graphical Comn arisons: Diversity Indices Cook Plant species diversity data for the years 1971 through 1976 have been presented and discussed by Ayers, Southwick, and Robinson (1977) and Ayers (1978). The tabulated data in those reports are for the most part not repeated here. This section is concerned with extending the previous discussions, tabulations, and figures to include the major surveys carried out in 1977. As was done in the report cited above, the diversity index data have been stratified by three depth zones and by inner treatment stations (near the plant) and outer control or reference stations groups. The diversity index used is, as previously, that of Wilhm and Dorris (1968): _ S d = - E (n /n) log (n./n) i=1 ^ ^ where S is the number of species, n is the total number of phytoplankton in cells/ml, n^ is the number of phytoplankton of the i^^ species. Mean diversity indices and associated standard errors for each depth-zone-station-group combination in 1977 have been computed and are presented in Table 5. In Figure 6 the surveys of 1977 have been added at the end of the time plots of diversity indices and standard errors which were presented by Ayers (1978). 37 TABLE 5. Means, standard errors, and numbers of observations of phytoplankton diversity indices by seasons, depth zones, and inner or outer station groups in Cook Plant major surveys during operational 1977. Previous years are reported in Ayers, Southwick, and Robinson (1977) and Ayers (1978). The diversity index used is that of Wilhm and Dorris (1968) based on log 2. Standard errors are computed only when the number of observations is two or more. 1977 Zone 0, Inner Mean S. E, N Outer Mean S. E, N Zone 1 , Inner Mean S. E, N Outer Mean S. E, N Zone 2, Inner Mean S. E, N Outer Mean S. E. N In Figure 6 the annual curves of mean diversity indices generally show substantial degrees of parallelism between inner and outer station groups, though parallelism was poor in all zones in 1971 and 1972, in Zone in 197^, and in Zone 1 in 1970 and 1973. Parallelism between the curves for inner (treatment) and outer (control) stations indicates that changes in diversity 4 April liilUii 14 October 4.24 0.11 12 3.92 0.08 12 4.06 0.22 12 4.23 0.08 10 3.84 0.08 9 3.92 0.13 10 4.19 0.08 3 3.73 0.16 3 3.67 0.42 3 4.13 0.28 4 3.44 0.21 4 3.54 0.34 4 4.18 0.13 2 3.29 0.21 2 3.19 0.40 2 4.06 0.20 4 3.73 0.13 4 2.84 0.20 4 38 utpr* ill z O IN 2 !r ^-Su O ^ < ^ O CO N O O 10 < *- 0) O CO N 0) O c\i N 0) < ^ Z r- N O joo in o 0") Q ui m i^ oj S30 1 a N 1 o rvi iD Al i 9^3 A la in d O CD SU O S 3 03 Sm O t. Cm £ iH C Cd 03 H CQ > 03 ^ X) O iH CU •H OQ SZ 03 H O •H •o • C C-- •H C^ o -u r •H O CO C-- •H C CO a • 3 73 o c s- o bO -H 4J 0) . CO M JJ X2 Ex. CQ O 4-) O 03 39 UJ z O N wj*r z t T ? ;^ 9. '^ S30 1 ON 1 q tT) A 1 ! S^ 3 Al a 'S) o o r^ o ^ < *- o in < ^ o m < ^ C^ 00 O ) 03 ^ X) T— iH CQ •H > T— 4-5 1 •H o CO >- Sm a^ •H c -o •H C CO 03 ex • •H Sh • 4-3 o— -t Ld Z O ? in o iD Q lO m ri S30 IQN 1 c iD Ai lSd3A 1 a If) d o ^. < ^ O CD < ^ O 10 P ^ < ^ O CO CD K ^ O CM < ^ z O 0^ o u CO > 03 jD -Q CVJ rH 03 Q) c •H o 4.^ N Ai4 o; c > •H 0) CO JZ > ^ 1 •H 00 >- t, a^ •H C •o H C CO 03 a • Q) 3 CO S c s^ bO-H • 4-> o C 03 VO > H ;^ • 4J» (U o m w M 4-:> ^ 1X4 CO 41 from season to season were the same in both sets of stations. Parallelism of the curves for inner and outer station groups in the operational years 1975 through 1977 has been as good as or better than in the preoperational years. The placement of annual curves on the graphs shows in all zones either a trend toward increasing diversity from 1972 through 1976 with no increase from 1976 to 1977 or (alternatively) an increase from 1972 through 1974 with a horizontal trend since that year. The meaning of these two trend possibilities is not now clear. Stoermer and Yang (1969, p. 212) point out that in Lake Michigan there has been a trend for diversity to increase with increasing eutrophication, rather than to decrease as might be expected from theory; if the lower data from 1977 are within normal annual variation, then increase due to eutrophication may be continuing. Alternatively, if the efforts toward reduction of phosphorus input to the lake are beginning to have effect, the upward trend due to eutrophication may be being halted. Data from additional years will be needed to clarify the question. There is no evidence from our diversity studies thus far that operation of the Cook Plant has adversely affected (lowered the diversity of) the local phytoplankton community in the operational years 1975 through 1977. Instead, the phytoplankton community has in the operational years continued to be more diverse than it was in the preoperational years prior to 1974. Inner-Outer Graphical Comparisons: Phvtoplankton Redundancies Redundancy values are derived from the diversity index of Wilhm and Dorris (1968): _ S d = - H (n^/n) log^ (n^/n) i=1 42 where S is the number of species, n is the total number of phytoplankton in cells/ml, n^ is the number of phytoplankton of the i^^ species. Diversity as presented here is not the true diversity since not all forms encountered can be identified to the species level. Therefore, this diversity must be viewed with caution. However, since these diversities do mean something about community structure they will be used to illustrate changes occurring within the phytoplankton population from year to year and for the derivation of redundancies. Redundancy is a measure of the dominance of one or a few species within a given population. As presented by Wilhm and Dorris (1968) it is: d - d max r = d - d . max mm where d is the observed diversity as calculated above, d is the maximum max diversity for a particular community, and d . is the minimum possible diversity for a particular community, d^^^ is calculated using the following equation: ^max = (^/n)(log2 n! - s log^ [n/S]!) and cl . is calculated using the equation: ^min = (^/n)(log2 n! - s log^ [n-CS-l)]!) The values of r range between and 1 . An r equal to implies that the species encountered in a community each have the same number of cells. An r equal to 1 implies that one species dominates the community of phytoplankton. Since redundancy values are not given in Appendix B, it is necessary to give them here (Table 6). The values for years 1970 - 1976 have been reported by Ayers (1978). Table 6 also presents the means, standard errors, and numbers of observations of redundancies in Cook Plant major surveys during 1977 stratified by seasons, depth zones, and inner and outer station groups. The means and 43 TABLE 6 . Means, standard errors, and numbers of observations of phytoplankton redundancies by seasons, depth zones, and inner and outer station groups in Cook Plant niajor sur^'eys during operational 1977. 14 April 1977 15 July 1977 14 October 1977 Zone 0, Inner Stations DC-0 0.236 0.260 0.204 DC-1 0.272 0.338 0.380 NDC-.5-0 0.275 0.400 0.263 NDC-.5-1 0.212 0.350 0,493 NDC-. 5-2 0.244 0.309 0.382 NDC-1-0 0.216 0.346 0.298 NDC~1-1 0.250 0.337 0,340 SDC-.5-0 0.416 0.329 0.231 SDC-.5-1 0.274 0.265 0.480 SDC-.5-2 0.346 0.324 0.420 SDC-1-0 0.260 0.342 0.155 SDC-1-1 0.268 0.304 0.324 Mean 0.272 0.325 0,331 S. E. 0.016 0.011 0.031 N 12-12 12 Outer Stations NDC-2-0 0.211 0.321 0.253 NDC-2-1 0.254 0.336 0.384 NDC-4-0 0.193 0.400 0.365 NDC-4-1 0.312 0.281 0.388 NDC-7-.1 0.230 0.307 0,320 SDC-2-0 0.227 0.334 0.350 SDC-2-1 0.264 0.308 0.272 SDC-4-0 0.318 0.300 0.369 SDC-4-1 0.25; 0.422 SDC-7-1 0.282 0.349 0,303 Mean 0.257 0.326 0.343 S. E. 0.014 0.012 0.017 N 10 9 10 Zone 1, Inner Stations DC-2 0.277 0.289 0.284 NDC-1-2 0.244 0.328 0.541 SDC-1-2 0.314 0.316 0.381 Mean 0,278 0.311 0.402 S. £. 0.020 0.012 0.075 N 3 3 3 Outer Stations NDC-2-3 0,227 0.340 0.416 NDC-7-3 0.261 0.317 0.329 SDC-2-3 0.384 0.458 0.479 SDC-7-3 0.255 0.447 0.501 Mean 0.232 0.391 0.431 S. E. 0.035 0.036 0,039 N . 4 4 4 Zone 2, Inner Stations DC-3 0.237 0.364 0.538 DC-4 0.308 0.426 0,408 Mean 0.298 0.395 0.473 S. E. 0.010 0.031 0,065 N 2 2 2 Outer Stations MDC-4-3 0,214 0.341 0.473 NDC-7-5 0.314 0.335 0.525 SDC-4-3 0,261 0.288 0.561 SDC-7-5 0.267 0.254 0,406 Mean 0.264 0.305 0.491 S. £. 0.021 0,021 0.034 N 4 4 4 44 standard errors are plotted on a time axis in Figure 7. The plots in Figure 7 show visual evidence of a trend, beginning in 1973, for redundancies to have become somewhat lower since that year. If real, the trend would indicate that there has been a tendency for the species in the community to have become more nearly equally abundant in numbers of individuals. Perhaps more important is that after 1972 there has been much better parallelism between the annual curves of redundancies at inae^ aia outer station groups, that is, changes in mean redundancies of collections from the two station groups have been much more alike than was the case in the earlier preoperational years. Since it began in the preoperational years and has continued into the operational years, the tendency for improved parallelism is attributed to some cause in the lake itself. There is nothing in this analysis of phytoplankton redundancies to indicate that the operation of Cook Plant has exerted any adverse impact on the local phytoplankton community. Inner-Outer Graphical Comparisons: Phvtoolankton Abundances Bv Algal Categories This section applies the inner-outer graphical analysis method to the abundances (in cells per ml) of ten major categories of phytoplankton and extends previously reported tabulations, figures, and discussions to include the seasonal surveys of 1977. Earlier years have been reported by Ayers, Southwick, and Robinson (1977) and Ayers (1978). The phytoplankton abundances used are those of total algae and of the nine major algal groups: coccoid blue-greens, filamentous blue-greens, coccoid greens, filamentous greens, flagellates, centric diatoms, pennate diatoms, desmids, and other algae. The use of major algal groups bypasses difficulties stemming from inability to always identify to species, and is justifiable on 45 Z o '■■\ UJ Ixi li UJ z O \ OJ d d o CO -) < *"■ o in -5 Q < '- o ^ rv -5 Q < '^ o CO r- -^ 0) < *" C\i -> < ^ z ^ rx -5 C7) < •~" z o N en O in d ADNVQNnaad CO Sm m (d Q) JD u CtJ rH CO 4J a C •H cd 4-5 r-4 S^ ffU > JiiJ O o CO Sm su 4-5 (D ^ CO CO X) CQ u o C O C CO X3 U rH C * O CO s: W H Q. CO a • CO ? a o M >> sz Es- -Q W 46 the basis that members of each individual group have more or less similar functions in the ecosystem. Table 7 presents, for the seasonal surveys of 1977, the means, standard errors, and numbers of observations of abundances of total algae and the nine major groups of planktonic algae in the three depth zones and the inner and outer station groups. These are graphed with the preceeding years in Figure 8. Desmids (Fig. 8A) have shown almost no variation in abundance over the entire eight years of the study. Filamentous green algae (Fig. 8B) , which in April 1976 had somewhat increased in abundance in both station groups and in all three depth zones, returned to preoperational levels in July of that year and have remained there ever since. Other algae (Fig. 8C) , increased in abundance in all depth zones and both station groups in 1976 and 1977, but similar abundances had been observed in preoperational years. There is no clear evidence that the recent greater abundances were plant-induced. Filamentous blue-green algae (Fig. 8D) have been more abundant in all depth zones and both sets of stations in the three operational years. In Zones and 1 increases at the outer stations equalled or exceeded those at the inner stations in all three years. In 1976 and 1977 in Zone 2 July abundances at the inner stations greatly exceeded those at the outer stations. Although these inner stations are in front of the plant, they are offshore stations where the plant's discharge plume is present little if any of the time; the increases at these stations appear more apt to be effects of lake eutrophication than of Cook Plant operation. Coccoid blue-greens (Fig. 8E), which had been present in small amounts during most of the preoperational surveys, increased notably in October of 47 03 c -C OJ ■u OJ a ;2 ^ a; cu 60 T3 (U 1 XI 0) •» 3 03 0) rH C > XJ CO w II CO Q) 03 c 03 M 1 CO « >> 0) ^ >^ 03 03 1—1 O 3 B a o c •H u d > 0) 'O 0) CL C )-i 3 Q^ 03 •a f—i CO • ^ r«* 0) C r^ CJ o 0^ 4J fH > D £ 03 a >» dJ • 14^ > >-N o U 00 r^ 03 3 CTn C »-H ^4 N-*' •H ;j •r-j 03 CO CO U > g . o ■u < 01 C J3 CO T3 rH C P4 CO U-l ^ /**«. P^ 03 l^ u CJ CJ\ X c 3 U CO O 3 •u O • 03 •73 w 03 C 3 « CO •« 03 03 ^ c u u ^ CO 0) ^ e r c < CO T-l fH >> •H T2 ^ M-l C c-^ CO ii •« 4J • w 03 u E ^J OJ o CO (23 C Ci- r-4 < OJ •H H ^a ^ nS4 o 5-1 0) 0) CO JJ rH O CO 03 TS •H a 03 0) c 0) 03 w a CO c XJ c CO — ^ CO • 03 a Q CO 01 •H }- O O a o CO O — i I o u a pa o o o CM o m O o ON c^ O 00 T CO in CN CN ^ 00 CO O in CN vD cn CN rH P-. O a\ CN cn T cn vO un r^ CN fH c^ C5> CM O^ ^ ^0 r^ f^ CN vO rH ON CN CN NO rH CN 00 CM r^. sO CN CN 00 CM vO CN cn cn » v^ CN C^ vO rH o o m cn o ^ r-i r-^ o o f^ in . cn <3- C^ ^ r^ cn ctn cn vo d vO CN C CO m r-1 o o m «n CN CN in CN CN ^T cn cn C O <• . C\ C^ cn cn in CN cn cn r-i 00 00 CM 00 00 rH CM CN m cr\ o O in rH cn 00 m CN o -l a; oj r-^ Qi a; C i-> c • 4H • C 3 ^ 3 3 W 3 c c=: H C M CO O CO &4 X c/2 z X cn OJ < c o rH o i-i V4 a; 0) 3 • ■u C 3 W 3 3 r-t CO O CO Oi 2: cn 2 2 u 3 W 3 3 M CO O CO s: cn 2 s CO 2 48 o en T3 •H a CO a> a Q) w U 6 ca c C 4J C en Q) •H Pm T3 CJ cn •H £ U •u u C CC cn 0^ ^T ^ as cn C r^ f^ ON CN ^ in rH r^ o> CN cn m r^ in on O r- in cr ^3- rH CN O rH on eg cn CO O vO cn ^ o o CN CN vO -vT vO O CJ> CN 00 CN r^ v,0 r^ CN O CN cn ,1 in cn CN cn CM oo' CN m 00 CN in 00 CN O 1^ OM on CN rH O 00 ON on CO CN vO on in <• O in "»3* o o cn CN CN CN o sr C^J rH VO rH in cn O --! rH rH in O .-1 fH m P-. m CN 00 on in 3- o o CN 00 CN r^ ^ on iH 00* rH on o m rH -^a- CM r^ C 00 P>. r^ r** on OM CN O O o in ON o in m CN on \o r^ m <■ O CN a\ ON vo c d- o c:n CN O CM in m CN a^ CN CN SO ON 00 on CN in vO so <• CN m on T3 0) 3 C e CO O •H cq fa O O a I O CJ O in on ON CN ON on cn ON in on fH SO 3" CM pH r^ 00 r^ CN ON d m CM . in m vO ON on r^ ON CJ\ <• 00 tH on a\ CN «H m o ON O r- r^ in on CN CN vO ON m m m in <■ o 0^ tn r^ 00 r^ CN vO 0^ . CO CN O 00 in \o en CN CT\ "^d- rH vC tH • • • e CVJ rH CN r* » in 00 rH P^ rH r^ vO cn r>» OS 3" O 3- CN d in CN o^ iH oo' 00* C7> on on vo * m , C^ u u rH U U u V-i }-< ^ a Q) Q) Q) cu a CU a C -u ci C • u • c • ■u • c • p • c = W r^ &3 a c Cs:3 c c Cz3 D j- C=4 c jU w 3 c w fH O PP M CO c CO M CO O s M CO O CO c OJ • (D • IJ • CJ • 0) • a • H CJ O s c/: 2 2 cn z 2 cn z s cn z 2 cn z z cn z 0) c c >3- tv3 rH o iH CN 50 • o is LOO UJNJ Q UJ z O N in o" Ixl Z O N lO d (s,000l) }UJ/S{|^D in d %0 !;< :o ;< in CO CM O o C7) O t. CO CO -o >> c J-5 CO o X3 rH «•-. CO •a c • 03 CO - 03 B B CO •H 03 t. -a a c CO 03 CO o • o • CO ^- u ^- 3 -O c 03 00 O (• J^ 51 < ^O c < 0) CD 1— 1 ',< <;-< CO "O CO ct3 4 o S^ A ^ -^ < - O § ^ 3 T3 • C CO g| : O S- CO C^ a ■"■ ^ in CQ c •H 55 < ^ c :5 •H CO Z ^ \ S. UJ UJ O 1 0) o w' • • eg 0) x: O 4J ^H ' UJ z UJ - < § I z N CO O !u -O 0) _j u. < C 00 dJ % CO C 0) 4J " -/'Si CO > « < r— S =5 £. « -? 00 o Cm 03 CO C^ in o «^ o in o CO C d o (S.COCI) lUU/Sil^O d • CO rH o CO ja M (D CO Ct. CO E-* 52 i 6 UJ < I- o \ LlI Z O rsi U Z O M 1 r^ Cm 1^ O 2 OQ •H SU CtJ (D C jQ o s (0 3 <« c CO s. o CO rH <*H K rH • o CO C^ .o d (s,OCOl) 0) -O rH CO CO to c •H a 4J 0) CO SU O CO C CO C\J CD x: O Ji o QQ x: sz s: o o c-« C3^ 00 r- 0) O JS C ttO CO D t3 O CO O C l>- CO CT\ 0) r- o CJ 00 CO CO >» > > c^ CO CO O o 53 II •SI z LiJ Ll! q: 9 LlJ 3o too O z LlJ < in d N.^ Z O N Cvj LU Z O If) O' (SOOCI) |UJ/S|!3D lO d SO n CM 0^ 1^ o 0) CTJ <;-* TD CO C t- CO o •> t. Sm (1) s -a B t^ Z3 CO CO CO tiO 4-> c CO •H Sm ^ ^ C •k Q) CD o 3 U rH o -o -Q s: c 3s CO CO 3 CO O • c ^ c^ o c c*- •H «H JZ^ S^ •H bO ^ D 00 O n » t- c o o CO > ^ o S-« s 3 CO • rH rH Q CO iD CO c CO o H • CO o CO M CD Cx- CO CO 54 £5 z UJ LU q: O I UJ Z) _J O UJ z O o u u o u -Kw-^: 1 ^ Id Z H o i \ \ K O CO CM U z o ^ -^ i CO o o CO O C E-» CD CO bO c •H a w o c\j c o Nl 05 c 4-5 CQ rH o ^ o o o o o CO O O o o o o to x: o x: > > CD 5h > SL* CO 3 XJ CO o 57 C9C» CD — O LiJ < UJ z o -o^s^ 1 I ftr-H UJ z O o -50 n Si z o (s,C00l) \lUfS\\ZO CO >> o o CO CO CO CO O O 58 LU zo Dl UJ z o irSH rvj U Z O rsl in 0^ ■••7 i t/) G) O f— ' CO CO c ^ o o TO jQ 03 S O 03 03 O c x: c H CD a o c^ CJ^ W «- CD O jC C bO OS 3 T3 O C Sh 3 x: JD 4.) 03 o 03 a^ • 5 > (D t. • > a Sm CO M 3 -Q Ct* CO O 59 but rather a combination of: (1) increasing nutrient loading; (2) summer epilemnetic silica depletions; and (3) a tolerant group of organisms. Concerning the latter, Stoermer, Bowman, Kingston, and Schaedel (op. cit., p. 365) say: "The elements of the phytoplankton flora which are common to both Lake Ontario and the upper lakes are those apparently eurytopic species such as Asterionella formosa [pennate], Fragilaria crotonensis [pennate], Ankistrodesmus falc^tus [other], Botrvococcus braunii [coccoid green], CrvDtomonas erosa [flagellate] etc. which enjoy almost universal distribution in both oligotrophic and eutrophic lakes." We note that the pennates Fragilaria crotonensis . Tabellaria fenestrata . and X- fenestrata v, intermedia have been frequent dominant or codominant forms in Cook Plant collections and consider this to be in harmony with the quotation above and with the paragraph on page 225 of the work cited where Tabellaria fenestrata is called common, widely distributed, and tolerant. Centric diatoms (Figs. 81, J, K) have varied widely in abundance during the period of study. Abundance variations at inner and outer stations have been directionally similar within each year but the annual patterns have been inconsistent from year to year. The expected summer minimum did not occur in any zone in 1977 nor in Zones or 1 in 1973. Fall recoveries in abundance did not occur in 1970, 1971, 1974, 1977, nor (except for the inner stations of Zone 2) in 1973. No clear effect of Cook Plant operation is discernable in the data on centric diatoms. Total algae (Figs. 8L,M,N) have, in all three depth zones and in both inner and outer station groups, exhibited steadily rising abundances since 1974; in Zone 2 the trend in abundance has been steadily upward since 1971. In Zone mean abundance levels in 1972 and 1973 were higher than a trend line from 1971 to 1974; in Zone 1 mean abundances in 1973 were higher than a trend 60 i 6 •is CO zo U iD 0^ n > 03 x: a\ x: O x: o c^ a> r— Cm O CO c o •H 03 > CD CQ O 61 I i 6 18 i-z zo u ; (SO CO I) \UJ/S\\ZO o CO r^ o "£ > 3 CQ < rH CO «M c o O CO CQ c CD CO ja r-- S -o o •H 5 < CO O E x: O en 4J Cd to n •H C- w -u Cd CVi =o -5 f^ o ^ O^ •H rH 5L, Cd 4J O < C -H 0) 4J o t- 0) ^ > z o 0) CO s: _ r^ O H ^ 0^ o r- c Cd • < -o C-- C C-- O en X2 r- cd s: T C fcO o Cd :3 « n 1^ 0) O CO ^ CD S Sm c *~ x: c •) ^ -H 4j »-5 O CT3 CO t- > a> L, . ^ (U cu CO M «M JO !X4 O O 62 * 6 11 in (J) UJNJ u en 0^ ^ O ; (/) o n C4 (s,000l) lUJ/SJOD CO >» > C cd o CO B C c jQ 03 0) CD CO 530 C •H . ^M CO CO o CsJ O C (d • jQ ON Sh O CO M "i-* ja IJu O O 63 id is UJ < CD > > o 0) JL > a; %. CQ 3 JD CQ O rH CiH OJ O C O CQ w u ^ CQ JD o CQ S 3 rH C r-l CO t. <;h O %^ -o C C-- CO O Oh o CQ C^ O c Cd •o c -Q cd c cd 0) CO 4^ a; > x: ON x: o x: 4-> (s,CCOt) \UJIS\\ZO • o Ct4 ^ 64 OJ O -5 CM O CO c u o o •H 4-i CO 03 >> > Q) t, > o ^ O w > CD O (D c s: 03 H 'O c =5 • X3 c^ 03 c- CT\ C t— 03 Q) x: S to :3 o • SL4 s: ^ CO 4-> . a ^- M o> Cz. (SOOCI) 65 < _J» > > a; S^ CO o: o CO o c O CO CO L, CO x: ON x: bfl O u x: 4-3 • o M ON CX4 r- (S.OCOL) !UJ/Si|3D 66 line from 1971 through 1972 to 197^. Trends of abundance increase in the flagellates, pennate diatoms, and blue-green algae have been commented upon; it appears that these algal categories are probably responsible for the trends in total algae. In depth Zone 0, parallelism between the annual curves of total algae abundance has been generally excellent and it is necessary to go back to 1970 and 1972 to find surveys wherein the standard errors of the means for inner and o iter station groups do not overlap. Parallelism between the curves for inner and outer stations has been if anything, better in the operational years than during preoperation. The increasing abundances in both station groups must be attributed to changes in the lake, not to Cook Plant operation. In Zone 1 , parallelism between the annual curves of abundances has been better in the operational years than it was in preoperational years. Except for April 1975, abundances in this zone have been coasistently higher in the outer station group. If plant operation results in heat stimulation of phytoplankton reproduction, as has been postulated, and with the plant's waste heat plume in the inner stations of Zone 1 most or all of the time, the higher abundances should have been at these stations; in eight of the nine operational surveys, however, the highest abundances were in the stations of the outer group. If plant operation results in phytoplankton inhibition at the inner stations of Zone 1, then inhibition should have been less (abundances higher) at these stations during 1975 when the plant was in the testing and power ascension phase than during 1976 and 1977 when the plant operated at higher levels and more consistently than in 1975; abundances at the inner stations, however, have continued to increase from 1975 through 1977. With the trends toward increasing abundances beginning at least as early as preoperational 1974, there is no clear evidence that operation of the plant has affected the 67 phytoplankton of Zone 1 . In Zone 2, parallelism between the curves of abundances at inner and outer stations has been, with the exception of July 1977, generally good since 1972. Except for July 1975 and October 1977, abundances of total algae have been greater at the inner stations in the operational-year surveys. With the plant's waste heat plume in Zone 1 most or all of the time, it would be unrealistic to attribute to plant heat the generally higher abundances at the inner stations of Zone 2. Abundances of total algae in both inner and outer stations of this offshore zone have been increasing quite consistently since 1971. Beginning during preoperation and continuing into the operational years, the increasing abundances reflect some change in the lake itself, rather than effects of plant operation. In the time sequences of total phytoplankton abundances there is no convincing evidence that Cook Plant operation has affected the local community; the changes observed appear to be expressions of the lake's continuing eutrophication. Inner-Outer Statistical Comparisons: Phytoplankton Abundances bv Alg;al C ^teg o r; Les, 1970-1977 Ayers (1978) reported preliminary statistical tests on total phytoplankton abundances (densities in cells per ml) at inner and outer station groups of shallow Zone and deep Zone 2 in the years 1970 through 1976. The test used was the 2-sample Students t. test. This section expands those preliminary statistical tests to include all ten categories of algae, the intermediate depth zone (Zone 1), and all three zones in the year 1977. The strategy was that if plant-caused effects on the phytoplankton were present they could be expected to show consistent significant differences in 68 cell densities between the inner and outer stations. Corollary to this was the possibility that plant operation might differently affect phytoplankters in the three depth zones and show consistent significant differences in the affected zone but not in the others. Another corollary was that plant operation might selectively act upon only one or a few of the ten categories of algae, producing consistent significant differences in densities of the affected categories between inner and outer station groups. For these tests spring was defined as March, April, and May; summer as June, July, and August; and fall as September, October, and November. For each season in each depth zone all available abundances of each algal category were averaged to give seasonal mean abundances at the inner and outer stations of each depth zone and comparisons were made between inner and outer mean abundances of each category in each depth zone. It was considered that lake-caused ?ibundance changes would similarly affect both the inner and outer station groups of each deoth zone in each season of each year. Table 8 gives for each algal category in each year, season, and station group the means, variance, number of observations, and T-test of significance in each depth zone. In Table 8 there are 591 paired comparisons of mean algal densities of which 350 are from preoperational years and 241 from the operational years 1975-77. In the eight years covered there were a total of 36 cases of significant differences of mean densities between inner and outer station groups; these amount to 6.0? of the possible comparisons. The following tabulation gives the distribution of the cases wherein there were significant (at the .05 or .01 levels) differences between mean densities of phytoplankton categories in inner and outer station groups. In each case the order of the abbreviations is: year, depth zone, season (Sp, 69 Su, Fa), and I or indicating which station group had the greater mean density of cells. Cases in operational years are underlined. Coccoid blue-greens 75 ^Zg r^a.]; Filamentous blue-greens 75iZ1,.Sy.Q 75iZ2,F^,I 7aiZ2,SuJ 77.Z2.Su,I Coccoid greens Filamentous greens Flagellates Centric diatoms Pennate diatoms Desmids Other algae Total algae 70,Z2,Su,I 71,Z2,Su,I 7^iZg,Fa,I 77,Z2,Su,I None 71,Z1,Su,0 72,Z2,Sp,0 73,Z1,Fa,0 74,Z2,Fa,0 76,Z2,F^,I 77iZ;ii3u,0 77,Z1,F^,0 72,Z1,Sp,0 72,Z2,Fa,I 7^,Z1,FaJ 7^,ZZ,V^,l 70,Z1,Su,0 71,Z2,Su,0 73,Z1,Sp,0 75.Z2.Fa.I 71,Z1,Su,0 71,Z2,Su,I 71,Z1,Sp,0 73,Z0,Sp,l 73,Z1,Sp,I 73,Z2,Fa,I 74,Z2,Sp,I 77i?2,Fa,I 72,Z0,Sp,0 72,Z2,Sp,0 76.Z1.SD.Q Summarized by years the cases of significant difference were: 1970 (2 seasons) 2 cases 1974 2 cases 1971 6 1Q7S A 1972 5 1Q76 1 1973 5 1977 L It is noted that the six cases of difference in operational 1975 and 1977 are not greater than the six that occurred in preoperational 1971; it is also noted that the four in operational 1976 are less than the five that occurred in preoperational 1972 and 1973- The numbers of cases by years appears to be within the natural range of variation, and no effect of plant operation is evident. Summarized by depth zones, with the station group having the greatest density of algae indicated and with operational year cases underlined, the cases of significant difference were: 70 -.—.:£ ^ C ' > -^ rsi CM C -"^ Ln 'sC i w w r. :0 -J w ^ = 3 ^ ■>C X — C .-M OX — rg 3 u c ^ cj v: C 1^ o ^ c ■n — r>s. u-^ C ^^ iT* r-j . . • -i • • O X C C X — — C^J JN vr XC^ XC XX ^-vc^ rs.i — II ^ i. >.^ ' Zi ^-v i. — sc ■A t: : j- — C c H ' Nli > i' a: "P ^ c ^ 75 X 1 M 72 2j c w ^ ^ u — i i/ i 73 u < >v t. — • v: II _: 3^ -- 1? in • • . 9 ^- J r^ -^ X 3 — o r^ XX -C — XX fj PV . . L'^ X — 3^ ii IJ > Si ,_, / ii 1; SC ^ ^ "^ ^ - -. P- 71 -T X rj ^ r-j c C C v/^ • tn rj C C C C C 5 c c c U-, i X ^^ — I c — — C C^ — 3> X ^ X i C C c — » 1^ O >jC • • • X f^ • c^ u-^ r» O CO sC un CO O rs. O tn r^ O O -"^ C >C C C r^ O O C C .-^ C ZC rsi o ^ O -^ L-^ r- » r; vT lt x -T — • X — X! O CNi o o o C X O ^ sC sC "" """ r-j rsi ~" -" — 3- ^ 3^ j^, ^ C 3? . !M — . f— o ? 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