ML19329C293
| ML19329C293 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 02/28/1979 |
| From: | Fletches J, Reutter J OHIO STATE UNIV., COLUMBUS, OH |
| To: | |
| Shared Package | |
| ML19329C282 | List: |
| References | |
| 106, NUDOCS 8002121003 | |
| Download: ML19329C293 (28) | |
Text
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CLEAR TECHNIC;.L REPORT NO.106
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PHYTOPLANKTON AND ZOOPLANKTON
. _ f' DENSITIES FROM LAKE ERIE NEAR THE u
DAVIS-BESSE Nilr' EAR POWER STATION i
DURinG 1978 s
Environmental Technical Specifications Sec. 3.1. 2. a.1 Plankton Studies (Phytoplankton and Zooplankton)
Prepared by Jeffrey M. P eutter James W.
Flet:ner Prepared for Toledo E ison Company Toleco, Chio l
THE CHIC STATE UNIVERS1Tr l
CENTER FCR L.AK E ERIE AR FA R ES EARCH CO LUMBUS, CHIO g00212 N F'ebruary 1979
3.1.2.a.1 Plankton Studies (Phytoplankton and Zooplankton)
Procedures Plankton samples were collected aoproximately once every 30 days from May through Novemoer from 7 sampling stations in the vicinity of Locust Point (Figure 1).
Samples could not be collected during April due to an unusually long winter and the presence of ice.
Four vertical tows, bottom to surf ace, were collected at each station with a Wisconsin plankton net (12 cm mouth; no.
20, 0.080 mm mesh).
Each sample was concentrated to 50 ml.
Two samples were preserved with lugol's and used for phytoplankton analysis.
Soda water was added to the remaining 2 samples to relax the zooplankters prior to preservation with 5% formalin.
The volume of water sampled was computed by multiplying the depth of the tow by the area of the net mouth.
Three 1-ml aliquots were withdrawn from each 50-ml sample and placed in counting cells.
Whole organism counts of the phytoplankton were made from 25 random Whipple Disk fields in each of the three 1-ml aliquots from 2 samples. When filamentous forms number 100 or more in 10 Whipple fields, tney were not counted in the remaining 15 fields. Identification was carried as far as possible, usually to the genus or species level.
All zooplankters within each of.the three 1-ml aliquots from 2 samples were counted by scanning the entire counting cell with a microscope.
Identification was carried as far as possible, usually to the genus or species level.
(
Phytoolankton Results.
Phytoplankters collected from tiay through November 1978 were divided into 54 taxa, generally to the genus level (Table 1). Fifteen taxa were grouped in 8acillariophyceae, 23 in Chlorophyceae,1 in Chrysophyceae, 2 in Dinophyceae, 1 in Euglenophyceae, 10 in Myxophyceae, and 2 in Protozoa.
Monthly mean phytoplankton populations ranged from 29,607/1 in July to 281,852/1 in May (Table 1). The mean dens.ity frcm all samples collected in 1978 was 109,768/1.
Phytoplankton densities at individual sampling stations ranged from 3,389/1 at Station 8 in Jua to 504,678/1 at Station 1 in May (Table 2).
Population pulses were observed in the spring and the fall (Figure 2).
The
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spring pulse was caused by diatoms while the fall pulse was caused by green algae (Figure 3).
Monthly mean bacillariophycean densities ranged from 915/1 in July to i
280,066/1 in May (Table 1). The annual mean bacillariophycean density from all
. samples collected during 1978 was 46,267/1 or 42 percent of the entire phytoplankton density. The dominant diatom taxa were Melosira sp. in May, June, and July; Asterionella formosa in August; and Fracilaria crotonensis in September, October, and November.
Melosira sp.
had the largest annual mean population, 18,972/1. Diatoms were tne cominant phytoplankton group in May when they constituted 99 percent of the entire phytoplankton population.
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TABLt 1 (Con't.)
MONTilLY MEAN POPULAT10tlS* OF IN0lV100AL PilYIOPLANKT0fl TAXA AT LOCllST POINT - 1978 TAXA itay June July Aug.
Sept.
- Oct, llov.
Crand 11 29 25 17 15 17 1
tlean CilLOROPilYCEAE (Green Algae)
Coelastrum sp.
0 0
13a 0
3 0
0 20 Cosmarium sp.
0 0
0 6
8 0
0 2
Dictyosphaerium sp.
0 0
982 1
0 0
0 141 Kirchneriella sp.
0 0
8 0
0 0
0 1
00cys tis sp.
0 7
0 6
4 0
7 4
Pediastrum duplex 102 579 441 312 202 2023 1466 733 Pediastrum simplex 225 36 607 441 916 1434 1166 689 Scenedesmus sp.
105 40 11 4
6 4
28 24 L Selenastrum sp.
28 0
0 0
0 0
0 A
Sgirogyra crassa 0
0 0
0 7
0 0
1 Spirogyra sp.
0 0
2 0
0 0
0 0.2 Stauras trum paradoxum 20 0
198 62 51 3
89 60 Tetraspora sp.
0 0
32 0
0 0
0 5
Trentepohlia sp.
0 0
18 0
0 0
0 3
Uniden ti fied 0
2117 0
0 0
0 0
302 Subtotal 482 2778 13026 4192 2845 27160 117566 24008 CilRYSOPilYSEAE (Brown Algae)
Dinobryon sp.
0 0
0 0
0 0
4 1
DIN 0PilYCEAE (Dinoflagellates)
Ceratium hirundinella 7
100 1164 54 11 0
0 191 PeridiiiTum sp.
0 0
2 0
2 0
0 1
Suhtotal 7
100 1166 54 13 0
0 192 EUGLENOPilYCEAE (Euglenas )
i Euglena sp.
0 0
0 0
4 0
0 1
TABLE 1 (Con't.)
fl0NTilLY f1EAN POPllLATIONS* Of
-lNDIVIDUAL PilY10 PLANKTON TAXA AT LOCUST P0lHT - 1978 May June July Aug.
Sept.
Oct.
flov.
Grand TAXA 11 29 25 17 15 17 1
Hean MYX0PilYCEAE (Blue-green Algae )
Anabaena spiroides-0 0
0 18 559 198 523 186 Anabaena sp.
0 239 53 15 371 802 446 275 Aphanizomenon flos-aquae 0
18071 13912 68825 74047 52362 15132 34621 Chroococcus sp.
0 0
94 0
0 0
0 13 Coelsphaerium sp.
0 3
0 0
0' 0
0 0.4 Herismopedia sp.
0 0
24 0
0 0
0 3
Microcys tis sp.
3 510 148 98 98 67 7
133
& Oscillatoria sp.
1289 3590 1011 85 502 6686 15530 3984 Raphidiopsis sp.
0 372 0
2 0
0 0
53 Uniden ti fied 0
0 0
0 0
53 14 10 Subtotal 1292 22784 14481 69043 75577 60169 31 rA' 39278 PROT 020A Domatomonas sp.
5 7
14 26 38 12 6
15 Unidenti fled flagellate 0
0 0
0 9
0 0
1 Subtotal 5
7 14 26 47 12 6
16 TOTAL 281852 31207 29607 76687 83484 99846 165699 109768 Expressed as no. of whole organisms / liter and computed fron duplicate vertical tows (bottom to surface) with a lliscnnsin plankton net (12 cm diameter, 0.080 nun mesh) from 7 sampling stations on dates indicated.
1 i
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TABLE 2 MON 1llLY HEAN PilYT0 PLANKTON POPULATIONS
- FROM SAMPLING STATIONS AT LOCUST POINT, LAKE ERIE - 1978 Station May June July August Sept.
Oct.
Nov.
Grand 11 29 25 17 15 17 1
Mean 1
504678 52904 24934 30122 69070 65157 260749
'143945 3
267168 15420 28707 48336 67592 226943 244023 128313 6
298575 33599 47841 36724 86274 88069 1720P,8 109024 E,
8 191915 3389 15871 116805 86739 71015 199435 97881 13 214234 42701 23913 119697 93823 77695 75855 92559 14 251516 33442 28692 95567 83979 64988 118171 96623 18 244880 36995 37254 89559 123929 105053 89567 103891 Grand Mean 281852 31207 29602 76687 83484 99846 165699 109768 s
Data presented as no. of whole organisms / liter and computed from duplicate vertical tows (bottom to surface) with a llisconsin plankton net (12 cm diameter, 0.630 mm mesh) at each station.
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FIG' RE 3 J
liONTHLY MEAN SACILLARIOPHYCEAE, CHLOC.0PHYCEAE, Att0 MYXOPHYCEAE POPULATICNS FOR LAKE ERIE AT LOCUST POINT, 1978.
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Monthly mean chlorophycean densities ranged from 482/1 in May to 117,566/.1 in November with an annual mean pooulation tram all samples collected during 1978 of 24,008/l or 22 percent of the total phytoplankton pcpulation (Table 1).
The dominant green algae taxa were Pedi strum sieclex in May; an unidentified specimen in June; Sinuclearia tatrana in Juiy, September, October, and November; and Botrvococcus suceticus in Auc;st.
31nuclearia tatrana had the largest annual mein p E at cn, 21,431/1.'
Chloropnyceae was tne dcminant phytoplankton class 1,1
- November, reoresenting 71 percent of the entire phytoplankto'n pcpulation.
Chrysophyceae was a rare class represented only by Dinobrycn sp.
It was present in samples from November, 4/1 (Table 1).
Dinophyceans were represented by 2 taxa, 0eratium hirundinella and Peridinium sp.
(Table 1).
Neither occurred in sa pies rom Octocer or hovemoer.
Ceratium hirundinella was the dominant of the two during the remaining montns.
Euglenophyceae was represented only by Euclena sp.
It occurred in September, 4/1 (Table 1).
Monthly mean myxophycean densities ranged from 1,292/l in May to 75,577/1 in September with an annual mean density from all samples collected in 1978 of 39,279/1, 36 percent of the total phytoplankton mean (Table 1). 'The dominant myxophycean taxa were Oscillatoria sp. in May and November and Achanizomenon flos-aouae eom June tnrougn October.
Achanizomenon exhibiteo tne largest annuai mean density, 36,621/1.
Myxophyceae was tne cominant algal class from June through October, representing 73 percent, 49 percent, 90 percent, 91 percent, and 60 percent, respectively, of the total phytoplankton population.
Protozoa, grouped here with the phytoplankton, was represented by 2 taxa, Domatomonas sp. and an unidentified flagellate.
Domatomonas occurred in every collection and was always the dominant of the two.
All raw data were keypunched O'1d are stored in Columbus, Ohio at the offices of tne Center for Lake Erie Area Research on the campus of The Ohio State University.
Analysis.
The Center for Lake Erie Area Research has monitored phytoplankton populations at Locust Point since 1974 (Figure 2).
Radical differences were noted between populations in 1974 and 1975, but 77 percent of the variation was explainable by variation in physical and chemical parameters of water quality (Reutter, 1976).
Bacillariophycean and Chlorophycean populations observed in 1974 and 1975 were quite comparable (Figures.4 and 5).
The Myxophycean component of the populations accounted for the differences between the 2 years.
No Myxophycean bloom occurred in 1974, whereas a huge Achanizomenon sp. bloom occurred in August 1975.
This bloom was highly correlatec with increased transparency (80 percent greater than in 1974) and decreased turbidity (20 percent of that observed in 1974) (Reutter, 1976).
A correlation of this type was first hypothesized by Chandler and Weeks (1945).
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O APRIL
. AAY JUNE JULY AUG SEPT OCT NOV 1
FIGURE 4-MONTHLY MEAN DACILLARIOPHYCEAE, CHLOROPHYCEAE, AND MYXOPHYCEAE POPULATIONS FOR LAKE ERIE AT LOCUST
- l FOINT - 1974.
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i 315 vs
-s 100 Bacillarlophyceae 90 N
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O APR MAY JUNE JULY AUG SEP'r OCT NOV DEC FICURE 5, MON fHLY MEAN 13ACILLARIOPllYCEAE, CHLOROPI-lYCEAE, AND MYXOPl (YCEAE POPULATIONS FOR LAKE ERIE AT LOCUST POINT - 1975.
Bacilliriophyceae and Chlorophyceae populations in 1976 were similar in size and :omposition to those observed in 1974 and 1975 (Figures 4, 5, and 6).
The diatom population, especially, was strikingly similar feca year to year, with 1976 nost resemoling 1974 Populations were always greatest in spring and f all, and pulses which began and ended abruptly ere comonplace. Chlorophycean populations tended to increase in the fall. A very small pulse was observed in June 1975 which was not observed in 1974 or 1976.
The 1976 Myxophycean population was between the extrames set forth in 1974 and 1975.
A bloom of Achanizomenon sp. occurred in July and August which corresponded well in time or occurrence with the 1975 August bloem, but, thcugh it was slightly longer la peak duration, it was only one third the magnitude of the 1975 bloom and started and ended much more abruptly.
Again, these pulses appear to be explainable by variation in transparency and turbidity.
Transparency in 1976 was similar to 1975 and much greater than 1974, while turbidity, though more variable than in 1974 or 1975, reached a low in July similar to that observed in 1975 and below that of 1974 (Reutter and Herdendorf, 1977).
The 1977 phytoplankton population exhibited diatom blooms in fall and spring as in preceding years, however, the spring bloom was approximately twice as large as those observed from 1974-1976 (Figure 7).
The myxophycean peculation showed pulses in sumer as in 1975 and 1976, but blue-greens also increased in the fall which was only hinted at in previous years. Chlorophycean populations were generally low and were very similar to those observed in 1974 and 1976.
The major' differences between 1977 and previous years were in the size of the spring and fall diatom pulses and the summer cyxophycean pulse.
- However, lack of a large cummer blue-green bloom was not unusual (1974) and the unusually long and cold winters of 1976-1977 and 1977-1978 undoubtedly had a 1arge influence on diatom densities as they are cold water forms.
Furthermore, the increase in the myxophycean densities in the fall of 1977 was due to Oscillatoria sp. which is also a cold water form.
The 1978 phytoplankton population exhibited spring and f all blooms and was very nearly a mirror image of the 1977 population (Figure 2).
However, the composition of this population was quite different from the 1977 population.
All three major components of the phytoplankton, diatoms, greens, and blue-greens, exhibited relatively large blooms during 1978.
The spring diatom bloom was the largest recorded to date, and its composition would indicate that it was probably much larger. The rationale for this statement is that approximately half the bloom was composed of Sceletonema subsalsa which is generally too small to be collected with an 80p plankton net.
Inererare, although Iarge numbers appeared in the sample, evea greater numbers were probably present but passed through the net. Consequently, this should not be viewed as a new species in the area, but rather a scecies which normally is not sampled by these methods.
Its presence at this time is probably due to clogging of the plankton bucket with the large Melosira so. population and suspended sediments. s T
FIG URE 6.
MONTHLY MEAN BACILLARIOPHYLEAE, CHLOROPHYCEAE, AND MYXOPHYCEAE POPULATIONS FOR LAKE ERIE AT LOCUST POINT,1976.
100,MO Bacillarlophyceae 90,000 __
Chlorophyceae 80,000 Myxophyceae
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FIG'JRE 7 CROFhYCEAE, AND MONTHLY MEAri EACILLAR'OPHYCEAE, C:2 MYXCPHYCEAE FCPULATIONS FOR LAKE ERIE AT LOCUET POINT, 1977.
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- 20.000 q 210.000 1i H1 s.
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The chlorophycean population was very similar to that observed in 1974 and 1977. However, the maximum wnich occurred in November was the highest observed for this grouo.
This peak was almost entirely due to a bloom of Binuclearia tatrana.
It thould be pointed out that a monthly sampling frequency for pianston can lead to this type occurrence.
It is also worth noting that Mougeotia sp. was absent.
Although never an extremely abundant taxon, it is usua i ly connon.
Recounting several samples indicated that although it was present, the numbers were so 10w that it was most often missed when counting 25 random Whipple Disk fields of view.
A check of similar samples collected throughout the Western Basin of Lake Erie for the' USEPA by the Center for Lake Erie Area Research, revealed a similar trend.
Myxophycean populations in 1978 were most like those from 1975 and 1976.
As usual, the dominant taxa were Achanizomenon and Oscillatoria.
In summary, phytoplankton populations observed at Locust Point during 1978 are similar to those of previous years and appear typical for those occurring in the nearshore waters of the Western Basin of Lake Erie.
Zooolankton Results. Zooplankters coll.ected May through November 1978 were grouped in 41 taxa generally to the species level (Table 3).
Twenty taxa were grouped under Rotifera,12 under Copepoda, 8 under Cladocera, and 1 under Protozoa.
Monthly mean densities ranged from 135/1 in November to 557/1 in Septemoer. The mean density from all samples collected in 1978 was 339/1.
Zooplankton densities at individual sampling stations ranged from 124/1 at Station 3 in May to 894/1 at Station 18 in September (Table 4).
Monthly mean rotifer densities ranged from 33/1 in June to 264/1 in May (Table 3).
The annual mean rotifer density for all semples collected in 1978 was 108/l or 32 percent of the entire zooplankton density. The dominant rotifer taxa during 1978 were Synchaeta spp. in May; Trichocerca multicrinis in June, July, and August; Polyartnra vulgaris in Septemoer ano hovemoer; and an unknown rotifer in October.
Polyartnra vulgaris had the largest annual mean density, 30/1.
Rotifera was tne cominant zooplankton group during May, Septemmer, October, and November constituting 89 percent, 38 percent, 49 percent, and 37 percent res::ectively, of the total zooplankton population. In contrast to this, rotifers constituted only 6 percent of the June population.
Monthly mean copepod densities ranged from 31/1 in May to 141/1 in August (Table 3). The mean copepod density from all samples collected in 1978 was 88/l or 26 percent of the entire zooplankton population. Cyclopoid nauplii dominated every month but August when Diaotomus siciloides was the dominant taxon.
Copepoda was the dominant zooplankton group in July and August representing 34 percent and 56 percent, respectively, of the total zooplankton population.
Monthly mean cladoceran densities ranged from 1/1 in May to 360/1 in June (Table 3).
The mean cladoceran density from all samples collected in 1973 was 118/l or 35 percent of the total zooplankton population. Cladoceran populations were dominated by Diachanosoma leuchtanbergianum in May; Eucosmina correconi
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TAllLE 3 (Con'l. )
M0flTilLY HEAN POPULATIONS OF INDIVIDUAL ZOOPLANKTON T'AXA AT LOCUST P0 lilt - 1978 May June July Aug.
Sept.
Oct.
Nov.
Grand TAXA 11 29 25 17 15 17 1
flean COPEPODA Cyclopoid Copepods Cyclops bicuspidatus thomasi 0.04 0.2 0.0 1.1 1.0 0.1 0.6 0.4 C. vernaTis 0.5 24.1 11.4 9.0 9.9 4.3 0.5 8.5 Mesocyclops edax 0.0 0.1 0.0 0.0 0.0 0.0 0.1 0.02 Tropocyclops prans nex 0.0 0.0 0.0 0.0 4.0 3.3 3.7 1.6 Copepodids, cyclop'oid 3.7 10.2 7.2 3.7 16.5 4.0 9.2 7.8 Naupleii,cyclopoid 17.9 55.2 73.9 5.2
- 46. fi 46.0 32.0 39.6 Subtotal 31.4 90.6 126.1 141.2 108.9 67.1 48.4 87.7 k CLAD 0CERA Bosmina 1
lon3 rostris 0.0 0.0 0.0 0.0 0.04 0.1 0.0 0.02 Chydorus sphaericus 0.0 1.3 33.5 30.2 83.7 9.8 11.7 24.3 Diaphanosoma leuchtenbergianug 0.3 0.1 0.1 2.3 4.8 0.6 0.1 1.2 Daphnia galeata mendote 0.0 0.1 0.3 0.1 0.04 0.5 0.2 0.2 D. retrocurva 0.2 71.1 42.7 13.6 44.5 16.2 1.9 27.2 Eubosmina corregoni (mature) 0.0 274.7 45.1 25.7 59.2 28.3 12.3 63.6 E. corresofd (ininature) 0.0 12.4 0.0 0.0 0.0 0.0 0.0 1.8 Leptodora kindlii 0.0 0.6 0.2 0.3 0.1 0.1 0.0 0.2 Subtotal 0.5 360.3 121.9 72.2 192.4 55.5 26.1 118.4 PROT 0ZOA DiffIunla sp.
0.0 33.4 83.9 0.9 49.9 3.4 10.8 25.0 10TAL 295.3 517.7 370.3 250.3 557.0 245.9 134.7 338.7 l
4
TABLE 4 MONIllLY HEAN Z00PLF,1KT0!! POPULAT10llS*
Fit 0M SAMPLING STATIONS AT LOCUST POINT, LAKE ERIE - 1978 Station May June July August Sept.
Oct.
Nov.
Grand 11 29 25 17 15 17 1
Hean 1
591.9 572.9 436.2 306.5 449.1 298.4 131.9 398.1 3
326.9 534.6 549.7 270.7 541.3 265.3 150.7 377.0 6
309.2 666.1 285.9 216.6 517.5 241.3 131.8 338.3 8
124.4 306.3 318.5 227.8 412.3 252.1 137.3 265.5 13 243.4 497.8 336.5 197.4 513.1 179.3 127.0 299.2 14 240.4 460.8 276.9 270.8 571.3 232.9 135.3 312.6 1 11 231.2 505.2 406.7 262.3 894.2 252.0 129.1 383.0 Grand Mean 295.3 517.7 370.3 250.3 557.0 245.9 134.7 338.7 Data presented as no. of organisms / liter and computed from duplicate vertical tows (bottom to surface) with a Wisconsin plankton net (12 cm diameter, 0.080 nmi mesh) at each station.
(mature) in June, July, October, and November; and Chydorus schaericus in August and September.
Eubosmina correccni (mature) nao tne largest annual ean density, 64/1.
Ciacocera was tne dominant zooplankton group only in June constituting 70 percent of the total zooplankton pcpulation.
Monthly "mean protozcan densities ranged from 0/1 in May to 84/1 in July (Table 3).
The annual mean density of 25/1 was 7 percent of the total zooplankton population.
Difflucia sp. was the only protozoan taxon.
Protoz:a was never the dominant zocpiancon group.
All raw data were keypunched and are stored in Columbus, Ohio at the offices of the Center for Lake Erie Area Research on the campus of The Ohio State University.
Analysis.
Zooplankton populations at Locust Point have been monitored since 1972.
In 1978, 2 new monthly lows were established for total zooplankton denstty.
Zooplankton densities observed during May and June were the lowest recorded to date although the June density was very s'milar to that observed in 1973 (Figure 8). Results from the other months of 1978 fell within the ranges established from 1972-1977.
Densities in July were slightly larger than 1977,,
slightly less than 1976, and less than those observed from 1972-1975. Densities observed in August were slightly larger than those observed in 1977, similar to those of 1973, and smaller than those of 1972 and 1974-1976. Densities observed in September of 1978 were greater than those cbserved during September of 1972 and 1975-1977 and virtually equal to those observed during September of 1973 and 1974 October densities were greater than those of 1972 and 1977 and less than those from October of 1974-1976. November densities were greater than 1977 and less than 1972-1976.
There are several plausible explanations for the variation which has occurred.
Samples in 1972 were collected with a 3-1 Kemmerer water bottle at the surface. From 1973-1978 samples were collected by a vertical tow, bottom to surf ace, with a Wisconsin plankton net. A brief comparison study in 1973 shawed that tne vertical tow captured approximately 50 percent more taxa than a 3-1 grab (Reutter and Herdendorf,1974).
The actual stations sampled have varied from year to year.
In 1973 the intake and discharge pipelines were being dredged, and in 1972, tropical storm Agnes affected the weather.
Due to the weather, samples were neither collected on the same day of the month each year nor spaced exactly one month apart. Hubschman (1960) pointed out the tremendous differences which occurred between daily samples, and these samples were taken monthly, while Wieber and Holland (1968) showed that even with replication, wide variation can occur due to patchiness in population densities. The high spring populations frem 1975 were undoubtedly largely due to early warming and lower turbidity as the total zooplankton population was significantly correlated with coth temperature and turbidity (r = 0.587 and -0.328, respectively) (Reutter, 1976).
Finally, operation of station circulating pumps was comon in 1976, 1977, and 1978.
Of the three main components of the zocolankton population, ratifer densities are by far the most erratic and unpredictable (Figure 9).
- However, densities observed in 1978 were generally within the bounds described by populations from 1972-1977.
The one exception was July when the censities 0
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observed were the lowest during the 7 year sampling period. Rotifer densities observed during May 1978 were greater than those observed during May of 1975 and 1977 and less than those observed during May of 1973,1974, and 1976.
July densities were greater than 1972, approximately equal to 1976 and 1977, and less than 1973-1975.
August densities were greater than 1977 and less than 1972-1976. September densities were greater than those observed in 1972 and 1975-1977 and less than those of 1973 and 1974. October densities were greater than those from 1972,1974,1975, and 1977, but less than those from 1976. November densities were greater than 1977 and less than 1972-1976.
Copepod populations are much more regular and predictable than rotifer populations (Figure 10).
They generally exhibit one peak per year and this usually occurs in the May/ June period. In 1978, one peak was observed, however, it occurred about two months later, July / August, and was smaller than those from previous years.
However, ~ due to the frequency of sampling arid the fact that peaks are always controlled by pulses of immature forms, this lower density in 1978 should not be considered too unusual as the peak may have been missed.
As with the copepod densities, cladoceran densities are quite regular and predictable.
They of ten exhibit two peaks, one in the spring and one in the fall (Figure 11). This was the case in 1978 which was extremely similar to 1975 and 1976.
In general these three years exhibited the greatest cladoceran densities followed by 1974 and 1977, which were very similar, and 1973 which was a poor year for cladocerans.
In sumary, due to the large variability observed in previous years, zooplankton populations observed in 1978 should be considered typical for the south shore of the Western Basin of Lake Erie.
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FIGURElt MONIllLY MEAN CLADOCERAN POPULATIONS FOR LAKE ERIE AT LOCUST POINT, 1972 - 1978.
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8912 3913 1974 1975 3916 3977 89/8
LITERATURE CITEL Chandler, D.C., and.0.3. Weeks.
1945.
Limnological studies of sestern Lake Erie V: relation of limnological and meteorological conditions to the production of phytoplankton in 1942.
Ecol. Monogr. 15:435 a56.
Hubschman, J.H.
1960.
Relative daily abundance of planktonic crustacea in the island region of western Lake Erie. Ohio J. Sci. 50:335-340.
Reutter, J.M. and C.E. Herdendorf.
1977.
Pre-operational aquatic ecology monitoring program for the Davis-Besse fluclear Power Station, Unit 1.
The Ohio State University, CLEAR, Columbus, Ohio.
205 pp.
Reutter, J.M.
1976.
An Environmental Evaluation of a iluclear Power Plant en Lake Erie; Scme Aquatic Effects.
Ph.D. Dissertation, The Ohio State University, Columbus, Ohio. 242 pp.
Reutter, J.M. and C.E. Herdendorf.
1974 Environmental evaluation of a nuclear power plant on Lake Erie.
Ohio State Univ., Columbus, Ohio.
Project F-41-R-5, Study I and II.
U.S. Fish and Wildlife Service Rept.
145 pp.
Wi eber,- P.H. and W.R. Holland.
1968.
Plankton patchiness:
effects en repeated nt tows.
Limnol. Oceanogr. 13:315-321.
4 6
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e-
X SgCTION 3 1.2.A.2 3
DENTHIC DTUDIES e
- --