Preliminary Results of the 1978-1979 Lake Erie


       Intensive Study - Phytoplankton
                    by

            David S. DeVault III

                   and

             David C. Rockwell
                    For

    U.S. Environmental Protection Agency
    Great Lakes National Program Office
      536 South Clark Street Room 102
           Chicago, Illinois 60605    %
             EPA-905-R-81-100

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                                         Introduction









       As part of the International Joint Commission's monitoring plan on the Great Lakes, intensive




surveys of Lake Erie were undertaken in 1978 and 1979 by the U.S. Environmental Protection Agency.




These surveys included monitoring of phytoplankton populations in the open waters on nine cruises in




each year (Table 1) to detect changes in the quantity and quality of phytoplankton reflective of changing




water quality and to provide data by which future changes may be measured. This report includes results




of the 1978-79 study as well as a discussion of changes occurring between 1978 and 1979.









                                               Methods









       Phytoplankton samples were collected according to the following sampling regime. When the




lake was thermally stratified, samples were collected from 1 meter, 1 meter above the metalimnion, at the




thermocline, 1 meter above the hypolimnion, and 1 meter above the bottom. When thermal stratification




was not evident samples were obtained at 1 meter, mid-depth, and 1 meter above the bottom. The




exception to this was on the March 1979 cruise when samples were obtained at the 1 meter depth from a




U.S. Coast Guard helicopter. Table 1 gives the cruise dates in 1978 and 1979.  In 1978 phytoplankton




samples were collected from all stations on all cruises (Figure 1). In 1979 a reduced station network was




implemented (Figure 2).









       Phytoplankton samples were obtained from the same opaque 8 liter Niskin bottles used for




nutrient-analysis. Following removal of water for nutrient analysis a 500 ml aliquot of sample was drawn




into an 540 ml polyethylene bottle and 10 ml of modified Lugols solution added. Samples were returned




to Chicago where analysis and quality control were carried out by USEPA's Central Regional Laboratory







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(CRL). In CRL the samples were shaken vigorously for several minutes and 10 ml poured into settling




chambers and allowed to settle for 35 to 48 hours.  Organisms greater than 10 |o.m were enumerated and




identified at 250 with 2 perpendicular strips 13.6 mm long (10.93 mm2) counted. Organisms less than 10




\i.m were enumerated and identified at 500 X with 2 perpendicular strips 13.6 mm long (5.55 mm2) being




counted. All analysis was performed using Lietz Ultralux inverted microscopes. All data was expressed




as cell/ml.









        Due to the large volume of samples generated and other commitments of Great Lakes National




Program Office (GLNPO); resources were not available for exhaustive station by station measurements




for the calculation of biovolumes. Instead the following regimen was used to generate approximate cell




dimensions for calculating biovolume. Organisms or cells were measured in surface samples from




stations 61, 84, 58, 50, 51, 86, 30, 79, 18, 80, and 5 on cruise numbers 4, 6, and 9 in 1978. At least 10




cells (usually many more) of each common species were measured. Less common species were measured




as they occurred. These measurements were combined and  mean dimensions calculated for each species.




Geometric shapes were approximated and mean volumes  calculated. When species not measured in this




process or were measured infrequently (n <10), biovolumes supplied by the Center for Lake Erie Area




Research at Ohio State University, State University of New York at Buffalo, or obtained from the




literature were utilized. Biomass was calculated assuming a density of 1.
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                                              Results
       Seasonal Variation 1978









       In 1978 total phytoplankton biomass in the western basin ranged from 2.0 g/m3 to 9.1 g/m3. Total




biomass (Figure 3) decreased from 2.0 g/m3 to 1.1 g/m3 between May and June before increasing to the




observed maximum of 9.1 g/m3in August. Following the August peak, biomass declined to 1.25 g/m3 in




November. The population was dominated (Figure 4) in turn by Diatomeae (May), Cryptomonadinae




(June), Dinophycinae (July), cyanophyta (August), Diatomeae (September-October), and Cyanophyta




(October-November). The seasonal variations in biomass of major taxonomic groups are given in Figures




5 and 6.









       Total phytoplankton biomass in the central basin in 1978 was less than that observed in the




western basin, ranging from 1.0 g/m3to 3.1 g/m3 (Figure 7). Biomass decreased from 2.8 g/m3 in May to




1.05 g/m3 in June before reaching the maximum observed value of 3.0 g/m3 in July. Following the July




maximum, biomass decreased steadily to the low of 1.0 g/m3 observed in November. The Diatomeae




dominated the plankton from May through late June (Figure 8). In July the population was nearly equally




dominated by the Chlorophyta (26%) and Dinophycinae (27%). The Chlorophyta continued to dominate




the central basin phytoplankton throughout the rest of the 1978 study period. The seasonal variations in




biomass of major taxonomic groups are given in Figures 9 and  10.









       The lowest total phytoplankton biomass and least seasonal variation in 1978 occurred in the




eastern basin (Figure  11) where biomass ranged from a low of 0.4 g/m3 in November to a high of 2.2 g/m3




in May. The major group composition (Figure 12) resembled that of the central basin with the Diatomeae







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dominating the plankton on the May and June cruises and the Chlorophyto dominating from July




through early October. The summer dominance of the Chlorophyta was, however more pronounced in




the eastern basin where it comprised over 88% of the total biomass. The seasonal variations in major




taxonomic groups are given in Figures 13 and 14.









       Seasonal Variation • 1979









       Caution should be exercised when considering seasonal variations in 1979. Vessel breakdown




and other technical difficulties resulted in data being available for seven cruises in the western basin, six




in the central and five in the eastern basin.









       The most complete data set in 1979 is for the western basin where total biomass ranged from a




low of 2.0 g/m3 in April to a high of 17.3 g/m3 in November (Figure 15). Biomass remained relatively




constant (2.0 g/m3 to 2.35 g/m3) on the April, May, and July cruises. By early August phytoplankton




biomass had increased to 15.7 g/m3 primarily as a result of large increases in Diatomeae (5.8 g/m3)




(Coscinodiscus rothii 3.1 g/m3) and Cyanophyta (7.3 g/m3) (Aphanizomenon  flos-aquae 3.6 g/m3)




biomass. Following a decrease to 12.3 g/m3 in September, total biomass again increased reaching 17.4




g/m3 in November.  The November peak resulted from very high 14.1 g/m3 Diatomeae biomass (Melosira




sp. 6.7g/m3, Stephanodiscus binderana 2.8 g/m3, S. Niagarea 2.5 g/m3) as well as a high Cyanophyta




biomass (2.1 g/m3)  (Aphanizomenon flos-aquae 1 g/m3). As  in 1978, the western basin phytoplankton




was dominated by the Diatomeae on the early cruises while  the Cyanophyta dominated the early to




mid-summer cruises (Figure 16) with the Diatomeae again dominating in September through November.




The seasonal variations in major taxonomic groups are given in Figures 17 and 18.
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       The central basin was similar to the western basin in that large diatom populations occurred on




the October (2.2 g/m3) and November (7.5 g/m3) (Melosira sp 3.5 g/m3, S. binderana 1.2 g/m3, S.




Niagarea 2.5 g/m3) cruises. In 1979 total phytoplankton biomass in the central basin ranged from 1.5 g/m3




to 8.4 g/m3 (Figure 19). The spring (March and May) cruises were dominated by the Diatomeae, with the




Chlorophyta dominating the plankton on the July cruise and the Diatomeae dominating on the September,




October and November cruises (Figure 20). The seasonal variations of major taxonomic groups in the




central basin in 1979 are given in Figure 17.









       Total biomass in the eastern basin in 1979 ranged from a low of 0.65 g/m3 in March to a high of




1.25 g/m3 in October (Figure 23). As in the central basin the spring cruise (March) was dominated by




Diatomeae. the summer (July through September) by Chlorophyta and the fall (October and November)




by Diatomeae (Figure-24). (Figures 25 and 26) give the abundance of major taxonomic groups.









       Species Composition









       The relative abundance of common species in 1978 and 1979 are given in Tables 2 through 7.




These tables also give the trophic preference of those species which have well defined trophic preference




(Stoermer and Yang 1970, Tarapchak and Stoermer 1976, Munawar 1981).









       The 1978 spring cruise (May 18-25) in the western basin was dominated by Melosira sp. with




Tabellaria fenestrata  and Closterium lunula as sub-dominants. The late spring (June 6-15 and June




23-July 2) cruises were dominated by Cryptomonas  erosa and Covata with Mougeotia sp. and Ceratium




hirundinella sub-dominants on the June 23-July 2 cruise. The three summer (July 19-September 6)




cruises were dominated by Ceratium hirundinella, Aphanizomenon flos-aquae, and Coscino discus rothii.







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Sub-dominants during this period included Cosmarium spp. and Melosira, spp. The fall cruises (October




3-November 16) were dominated by Oscillatroia sp. with Melosira sp. and Coscinodiscus rothii as sub-




dominants.









       In 1979 the early spring cruises (March 27-April 20) in the western basin were dominated by




Fragillaria sp. and Melosira sp. with Diatoma tenue and Stephanodiscus binderanus sub-dominate in




April. The summer period (July 11-August) was, as in 1978, dominated by Aphanizomenon flos-aquae




with Ceratium hirundinella and Coscinodiscus rothii as sub-dominants. The fall (September




11-November 16) cruises were dominated by Melosira sp., and Stephanodiscus niagarae with




Coscinodiscus rothii, Aphani zomenon flos-aquae, and Stephanodiscus binderanus as sub-dominants.









       The 1978 spring (May 18-25) cruise in the central basin was dominated by Asterinonella formosa




with Melosira sp. a sub-dominant. By late spring (June 6-July 2) an unidentified non-green flagcallate




and Fragilaria crotonensis were the dominant phytoplankton organisms with Cryptomonas erosa and an




unidentified pennate diatom important contributors to the total biomass. The summer (July 19September




6) cruises were dominated by eutropic forms, such as Ceratium hirundinella and Oocystis borgei with




other eutrophic species such as Aphanizomenon flos-aquae. Stephanodiscus niagarae, and Scenedesmus




bijuga common. The fall (October 3-November 16) cruises were dominated by Stephanodiscus niagarae.




and Cryptomonas erosa. Oscillatoria sp. and Crvptomonas ovata were sub-dominates. Eutrophic




indicators such as Aphanizomenon flos-aquae, Oocystis borgei; and Oscillatoria sp. were, common.









       In 1979 the central basin spring (March 27-May 26) cruises were dominated by the




Stephanodiscus niagarea with Stephanodiscus binderanus, Diatoma tenue var. elongatum, Fragilaria sp.,




Melosira sp., Tabellaria fenestrata, and Rhodomonus minuta common. The summer (July 11-August 4)







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cruises were dominated by Ceratium hirundinella with eutrophic indicators such as Coelastrum




reticulatum, Staurastrum paradoxum, Oocystis borgei, Aphanizomenon flos-aquae. and Coscinodiscus




rothii common. The fall cruises (September 11-November 16) were dominated by Stephanodiscus




niagarea in September and October while Melosira sp. dominated the November cruise.









       In the eastern basin the spring 1978 (May cruise was dominated by Stephanodiscus binderanus




with Asterionella formosa a sub-dominate. By late spring (June 6-July 2) an unidentified pennate diatom




and Cryptomonas erosa were the dominant and subdominant species. Diatoms such as Fragilaria




crotonensis, and Tabellaria fenestrata were important.









       The summer (July 19-September 6) cruises were dominated by eutrophic green and blue-green




species such as Anabaena flos-aquae, Scenedesmus bijuga, and Oocystis borgei. Other typically




eutrophic forms such as Ceratium hirundinella and Staurastrum paradoxum were common. By the fall




(October - November) cruises diatoms were becoming relatively more important in the plankton with




Tabellaria fenestrata and Stephanodiscus niagarea common. The fall 1978 cruises were dominated in turn




by Oocvstis borgei. Tabellaria fenestrata, and Cryptomonas erosa.









       In 1979 only five phytoplankton cruises were completed in the eastern basin.  Three of these




were clustered in the September-November period. The Spring (March) cruise was dominated by




Stephanodiscus niagarea which comprised over 78%  of the total biomass. The summer and fall cruises




for which data is available indicates a successional pattern similar to that observed in  1978.
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       Horizontal Variation









       Figures 27 and 28 illustrate the horizontal distribution of total biomass in 1978 and 1979. In 1978




a growth pulse had apparently begun in the central and stern basins prior to our May cruise. A second




pulse began in the western basin on the June 28 cruise which spread into the central and eastern basins in




July. Throughout the 1978 study season total biomass tended to be higher near shore in all basins. The




western basin, particularly west of the Detroit River and southwest of the Bass Islands exhibited the




highest total biomass. Biomass concentrations in the central and eastern basins were surprisingly similar.









       In 1979 total biomass at most stations in the western and central basins (from August through




November) was substantially higher than that observed in 1978 while eastern basin concentrations were




relatively unchanged from the previous year.
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                                              Discussion









       In both years of the study there was a west to east decrease in total biomass and change in




dominant groups. In 1978 mean total biomass ranged from 4.0 g/m3 in the western basin to 1.8 g/m3 in the




central and 1.2 g/m3 in the eastern basin. In 1979 the reduced station network and limited number of




cruises yielded mean biomass of 9.4 g/m3, 3.4 g/m3, 0.9 g/m3 in the western, central, and eastern basins




respectively. Between May and November, both years, the Cyanophyta was most common in the western




basin, the Diatomeae in the central and the Chlorophyta in the eastern basin. The large dominance of




diatoms on the April cruise in 1979 resulted in the Diatomeae being the dominate form in the, western




basin that year. (Munawar and Munawar (1976) reported similar dominance of major groups in the three




basins between April and December 1970.









       The major observation of our study was the increase in phytoplankton biomass observed between




1978 and 1979 in the western and to a lesser extent in the central basin. This was particularly evident in




the western basin where a nearly complete data base in 1979 and similar station locations in 1970, 1978,




and 1979 allows a more direct comparison than can be made in the other basins. Figure 29 illustrates the




cruise means for total phytoplankton biomass in 1970 (Munawar and Munawar 1976), 1978, and 1979 at




stations 50, 51, 55, 58, and 61. The data  indicates that western basin biomass between April and August




in both 1978 and 1979 was substantially below that observed in 1970. However, in the latter portion of




the 1979 season total biomass frequently equalled or exceeded that observed in 1970.









       While the lack of May and June cruises in 1979 prevents direct comparison over the season, the




data can be compared for the July through November period. This is given in Table 8 and shows the large




biomass increase over 1978 levels that occurred in the later half of 1979. This increase is supported by







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field observations of visible blue-green algae blooms over large areas of the western basin in August,




September, and October 1979. We also observed blooms associated with whitings (Schelski & Callender




1970) probably as a result of CaCO3 precipitation, in August 1979.









       Vollenweider (1968) has used maximum phytoplankton biomass as an indicator of trophic status.




He classifies lakes with maximum biomass <1.0 g/m3 as ultra-oligotrophic, 3 to 5 g/m3 as mesotrophic




and those >10 g/m3 as highly eutrophic. Based on this system, the western basin of Lake Erie would be




classified between mesotrophic and highly eutrophic (9.1 g/m3) in 1978 and as highly eutrophic (17.3




g/m3) in 1979. The central basin would be considered mesotrophic (3.1 g/m3) in 1978  and between




mesotrophic and highly eutrophic (8.4 g/m3) in 1979. The eastern basins with maximum biomass of 2.2




g/m3 and 1.25 g/m3 would be considered mesotrophic both years.









       The above classification is consistent with the trophic preference of common  species given in




Tables 2 through 7.  In the western basin; between  44% (in 1978) and 62% (in 1979) of those species




comprising 5% or more of the total biomass have been classified by at least one author as eutrophic. In




the central basin 41% and 55% fall in this category in 1978 and 1979. The percentage of eutrophic




species in the eastern basin in 1979 may be influenced by the limited number (5) of cruises.









       As the largest phosphorus loading and the most complete data bases are from the western basin,




the reminder of this discussion will be directed at that basin.
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       Heterotrophic bacterial populations have been shown to be sensitive to minute changes in




nutrient concentrations and are thus sensitive indicators of nutrient changes (Godlewska and Lippowa




1976, Rao and Jurkovic 1977). Heterotrophic bacterial populations in the western basin increased from




an annual geometric mean of 478 organisms/100ml in 1978 to a geometric mean of 526 organism/lOOml




in 1979.  The highest bacterial populations in both years were observed in the areas influenced by the




Detroit River, River Raisin, and Maumee River (stations 60, 61, 75, and 84). In 1978 the annual




geometric mean for the above  stations was 1136 organisms/lOOml with a maximum observed population




of 21500 organisms/lOOml at station 60 during the October-November cruise. In 1979 the annual




geometric mean for these stations increased almost three times to 3150 organism/lOOml with a maximum




population of 115,000 organisms/lOOml  observed at station 60 during the May cruise (#2). There were




three occurrences of populations >5000 organisms/lOOml in 1978 and seven in 1979 in this area (USEPA




- unpublished data). The increased bacterial activity observed in 1979 is in agreement with the larger




phytoplankton biomass and is  suggestive of increased nutrient concentrations.









       Unfortunately total phosphorus data is not available for a large portion of the 1978 study period.




However, during those periods for which data are available, western basin concentrations were higher in




1979. Total phosphorus concentrations from May through July averaged 18.8 ug/1 and 19.0 ug/1 in 1978




and 1979 respectively. This excludes the western basin mean of 98 ug/1 which was observed in April




1979, following severe storms. In 1979, a mean total phosphorus concentration of 29.3 ug/1 was observed




in the August through October period. While data is not available  for this period in 1978, comparison of




the November cruises in each  year suggests that total phosphorus concentrations in the later portion of




the 1979 season were as much as 50 percent higher than that observed in 1978. The mean western basin




total phosphorus concentration in November 1978 was  22.3 ug/1 compared to 32.7 ug/1 in 1979 (Fay and




Herdendorf 1981). Total phosphorus concentrations also increased from 1978 to 1979 in the central and







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eastern basins. During the periods for which data is available (May-November) total phosphorus in the




central basin averaged 8.4 ug/1 in 1978 and 12.1 ug/1 in 1978. In the eastern basin (May-August) total




phosphorus averaged 9.5 ug/1 in 1978 and 11.7 ug/1 in 1979 (Fay and Herdendorf 1981). The increase in




total phosphorus concentrations which occurred in 1979 supports, and probably contributed to, the




increased phytoplankton biomass.









       It must be noted, however, that total phosphorus loads to the western basin decreased by 1075




metric tons (Yaksich and Melfi 1982) from 1978 to 1979. A period during which biological and chemical




data indicates that increased concentrations occurred, particularly in the western basin. Changes in lake




levels may be responsible for part of the concentration change. Water levels were 30 to 122mm below




1978 levels the first half of 1979, and 30 to 122mm above 1978 levels during the last six months of 1979.




As a result, the mean western basin volume for the two cruise seasons was relatively constant, averaging




24.41 Km3 in 1978 and 24.79 Km3 in 1979 (Fay and Herdendorf 1981). It is evident that while some of




the increase in total phosphorus concentration may be the result of complicated interactions between




loading and lake level, the majority must be explained by other mechanisms.









       One possibility is that the increased loads of orthophosphorous (Table 9) in 1979 resulted in an




increase biologically available phosphorus despite the decrease in total  phosphorus loading. The




bioavailability of the phosphorus from tributary loads ranges from 1 to 55 percent depending on the




contributing source of the phosphorus. Cowen and Lee (1976) reported that available phosphorus




comprised 5 percent or less of the total phosphorus in particulates in tributaries and from 1 to 24 percent




of the total phosphorus in urban run off to the Genessee River. Algal available phosphorus ranged from 0




to 50 percent (mean 22.7%) of the total particulate phosphorus in  several tributaries to Lakes Erie and




Ontario (Maumee River, Sandusky-Honey Creek, Cuyahoga River, Cattaraugus Creek, Genessee River)







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(Martin et al 1982). If biologically available phosphorus comprised 13 percent or less of the total




tributary load to Lake Erie the 146 metric ton increase in the orthophosphorous load may have resulted




in an increase in biologically available phosphorus despite the decreased total phosphorus load.









       That this may have occurred is suggested by the timing of the biomass increase, precipitation




events, and orthophosphate load in 1979 (Table 9). Precipitation was significantly above 1978 levels in




July, August, and November 1979. While Table 9 indicates that annual total phosphorus loads were




reduced in 1979, orthophosphorous loads were above 1978 levels from July through December 1979 with




the exception of October. In addition, during August and November 1979, total phosphorus loads




exceeded  1978 loads. Thus, probably not coincidently, total biomass increased dramatically from




mid-July to early August and remained high throughout the remainder of the 1979 season.









       The results of the 1978-79 intensive study indicate that severe deterioration in water quality




occurred in the last half of the 1979 study. While chemical (phosphorus) data is lacking for a good




portion of 1978, the consensus of the data overwhelmingly indicates that deterioration in water quality




did occur. The increased phytoplankton biomass and bacterial activity in 1979 may have been a result of




the increased loads of bioavailable phosphorus that occurred in spite of the decrease in total phosphorus




loadings. Orthophosphorous loads to the western basin increased by 146 metric  tons during the study,




from 3742 metric tons in 1978 to 3888 metric tons in 1979. The Detroit River contributed 116 metric




tons of this increase (Yaksich and Melfi 1982).
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       The increase in orthophosphorous loading may have resulted from combined sewer overflows




and runoff due to the increased precipitation. Combined sewer, overflows from 25 major events




contributed 160 mt TP in the Detroit area (Giffels, Black, and Veatchs 1981) in 1979 (Table 9). This load




was estimated to be 50 mt above a normal rainfall year.
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                                             References









    Cowen, W. F. and G. F. Lee. 1976. Algal nutrient availability and limitation in Lake Ontario during




IFYGL. Part I. Available phosphorus in urban runoff and Lake Ontario tributary waters. USEPA




EPA600/3-76-094a. 217 p.









    Fay, L.A. and C. E. Nerdendorf. 1981. Lake Erie water quality assessment of 1980 open lake




conditions and trends for the preceeding decade. CLEAR, Ohio State University. 161 p.









    Giffels, L., J.R. Black and I.F. Veatch. 1981. Quantity and Quality of combined sewer overflows.




CS-806. Final Facilities Plan, Interim report. City of Detroit, Water and Sewage Department.









    Martin, S.C., J.V. Depinto, and T.C. Young.  1982. Estimation of phosphorus availability for Great




Lakes tributary sediments using chemical and algal assay techniques. 25th Annual Meeting of the




International Association for Great Lakes Research. Abstract.









    Munawar, M. 1981.Response of nannoplankton and net plankton- species to changing water quality




conditions. Canada Center for Inland Waters. 20 p.









    Munawar, M. and I.F. Munawar.  1976. A lakewide study of phytoplankton biomass and it's species




composition in Lake Erie, April-December 1970. J. Fish Research Board, Canada 33: 581-600 pp.









    Schelske, C.L., and E. Callender. 1970. Survey of phytoplankton productivity and nutrients in Lake




Michigan and Lake Superior. Proc. 13th Conf. Great Lakes Res., Int. Assoc. Great Lakes Res. 93-105 pp.







                                           Page -15-

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     Stoermer, E.F. and JJ. Yang. 1970. Distribution and relative abundance of dominant plankton




diatoms in Lake Michigan. Great Lakes Research Division, University of Michigan publication No. 16.




64 p.









     Tarapchak, S. J. and E. F. Stoermer. 1976. Environmental status of the Lake Michigan region.




Vol. 4. Phytoplankton of Lake Michigan ANL/ES 40, Argonne National Laboratory. 211 p.









     Yaksich, S.M., D.A. Melfi, D.A. Baker, and J.A. Kramer. 1982. Lake Erie nutrient loads 1970-1980.




25th Annual Meeting of the International Association for Great Lakes Research. Abstract.
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                                     Table 1

                          Lake Erie Cruise Dates 1978 -1979
Cruise
Number                     1978                              1979

   1                                                         March 27-29
   2                       May 18-25                         April 17-20
   3                       June 6-15                          May 15-26
   4                       June 23 - July 2                     sediments only
   5                       July 19-29                         July 11-19
   6                       August 8-16                        July 31-August 4
   7                       August 29- September 6              ship failure
   8                       October  3-12                       September 11-21
   9                       October  24 - November 1             October 4-10
   10                     November 7-16                     November 7-16
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                                       Table 2

                   Seasonal Relative Abundance of Common (>5%)
                          Species in the Western Basin 1978
Cruise

May 18-25
June 6-15
June 23- July 2
July 19.-20
August 8-16
August 29 - September 6
Species

Melosira spp.
Tabellaria fenestrata
Closterium Lunula
Unidentified pennate diatom

Cryptomonas erosa
Cryptomonas ovata
Tabellaria fenestrata
Cosmarium spp.
Unidentified non-green flagellate
Rhodomonas minuta

Cryptomonas ovata
Cryptomonas erosa
Mougeotia spp.
Ceratium hinrundinella  •
Aphanizomenon flos-aquae •

Ceratium hinrundinella  •
Cosmarium sp.
Aphanizomenon flos-aquae •
Cryptomonas erosa
Cryptomonas ovata

Aphanizomenon flos-aquae •
Coscinodiscus rothii •
Melosira spp.

Coscinodiscus rothii •
Aphanizomenon flos-aquae
Melosira spp.
Stephanodiscus niagarae
Oscillatoria spp.  •
Anabaena spp.  •
   Percent of
Total Biovolume

       34.43
       16.28
       15.11
        7.57

       32.74
       12.63
        9.20
        7.16
        6.11
        5.41

       14.57
       12.89
       12.84
       10.03
        7.30

       53.79
       11.99
        7.99
        7.11
        6.07

       49.50
       14.38
       11.88

       28.62
       14.13
       11.58
        9.28
        6.58
        5.14
                                     eutrophic species

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Cruise

October 3-12
October 24 - November 1
November 7-16
                                  Table 2 (Continued)
Species

Oscillatoria sp.  •
Melosira spp.
Coscinodiscus rothii  •
Anabaena spp.  •
Stephanodiscus niagarae
Pediastrum simplex  •

Oscillatoria spp.  •
Melosira spp.
Anabaena spp.  •
Mougeotia spp.

Oscillatoria spp.  •
Melosira spp.
Coscinodiscus rothii  •
Mougeotia spp.
Tabellaria fenestrata
Dinobryon spp.
    Percent of
Total Biovolume

      18.60
      17.82
      12.32
      6.85
      6.40
      6.16

      31.04
      16.40
      8.32
      5.68

      26.73
      15.04
      6.42
      5.88
      5.73
      5.06
                                      eutrophic species
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                                        Table 3
                     Seasonal Relative Abundance of Common (>5%)
                            Species in the Western Basin -1979
Cruise

March 27-29
April 17-20
May 15-26

July 11-19
Species
    Fragilaria spp.
    Tabellaria fenestrata
    Stephanodiscus niagarae  •
    Melosira spp.
    Stephanodiscus binderana
    Unidentified Centric Diatom
    Unidentified non-green flagellate
    Diatoma tenue var. elongatum  •
    Asterionella formosa
    Fragilaria crotonensis

    Melosira spp.
    Diatoma tenue var. elonatum  •
    Stephanodiscus binderana  •
    Tabellaria fenestrata
    Stephanodiscus niagarae  •

    No data

    Aphanizomenon flos-aquae •
    Ceratium hirundinella  •
    Cryptomonas erosa
    Coscinodiscus rothii •
    Cryptomonas ovata
    Percent of
Total Biovolume

      17.02
      9.71
      9.59
      8.51
      7.92
      7.54
      6.90
      6.00
      5.77
      5.01

      29.54
      15.49
      14.18
      7.49
      6.24
      18.43
      16.82
      11.57
      6.70
      6.14
July 31-
  August 4
    Aphanizomenon flos-aquae
    Coscinodiscus rothii •
    Anabaena spp.  •
    Melosira spp. •
    Anabaena spiroides  •
     23.10
     19.48
       9.95
       8.18
       7.49
                                      eutrophic species
                                      Page -20-

-------
                                  Table 3 (Continued)
Cruise

September 11-21
September 4-10
October 7-16
Species

Melosira spp.
Stephanodiscus niagarae  •
Coscinodiscus rothii  •
Aphanizomenon flos-aquae  •
Anabaena spiroides  •
Anabaena spp. •

Stephanodiscus niagarae  •
Melosira spp.
Aphanizomenon flos-aquae  •
Gyrosigma spp.
Pediastrum simplex  •
Stephanodiscus binderana  •

Melosira spp.
Stephanodiscus binderana  •
Stephanodiscus niagarae  •
Aphanizomenon flos-aquae  •
Diatoma tenue var. elongatum
    Percent of
Total Biovolume

     16.71
     12.54
     12.21
     10.93
      7.66
      6.38

     22.73
     12.93
     11.96
      8.10
      5.32
      5.13

     38.45
     17.82
     14.59
      6.01
      5.07
                                      eutrophic species
                                      Page -21-

-------
                                     Table 4
                Seasonal Relative Abundance of Common (>5%)
                        Species in the Central Basin 1978
Cruise

May 18-25
June 6-15
June 23 - July 2
July 19-29
August 8-16
Species

Asterionella formosa
Melosira spp.
Fragilaria crotonensis
Stephanodiscus niagarae  •
Stephanodiscus binderana  •

Unidentified non-green flagellate
Unidentified pennate diatom
Rhodomonas minuta
Tabellaria fenestrata
Cryptomonas erosa
Fragilaria crotonensis

Fragilaria crotonensis
Cryptomonas erosa
Unidentified non-green flagellate
Stephanodiscus niagarae  •
Rhodomonas minuta
Cryptomonas ovata
Tabellaria fenestrata

Ceratium hirundinella  •
Aphanizomenon flos-aquae  •
Stephanodiscus niagarae  •
Cosmarium spp.

Ceratium hirundinella  •
Aphanizomenon flos-aquae  •
Oedogonium spp.
Unidentified coccoid green
Scenedesmus bijuga  •
    Percent of
Total Biovolume

      31.92
      18.08
      6.44
      6.40
      6.39

      27.95
      13.06
      9.48
      8.70
      8.54
      7.25

      15.72
      11.42
      12.21
      9.64
      8.32
      7.32
      6.77

      29.34
      8.00
      7.59
      5.10

      21.93
      13.30
      9.61
      5.49
      5.13
                            eutrophic species
                                    Page -22-

-------
                            Table 4  (Continued)
Cruise

August 29 -
  September 6
October 3-12
October 24 -
  November 1
November 7-16
Species

  Oocystis borgei   •
  Aphanizomenon flos-aquae  •
  Unidentified coccoid green
  Scenedesmus bijuga •
  Oocystis spp.
  Oocystis pusilla

  Stephanodiscus niagarae  •
  Cryptomonas erosa
  Aphanizomenon flos-aquae  •
  Unidentified pennate diatom
  Oocystsi borgei  •
  Oocystis spp.

  Cryptomonas erosa
  Oscillatoria sp.  •
  Cryptomonas ovata
  Oocystis borgei  •
  Stephandiscus niagarae  •
  Unidentified coccoid green

  Cryptomonas erosa
  Cryptomona ovata
  Oscillatoria spp.  •
  Stephanodiscus niagarae  •
    Percent of
Total Biovolume

      17.68
      11.53
      8.79
      8.79
      7.60
      5.75

      12.53
      6.56
      5.81
      5.71
      5.60
      5.22

      13.85
      11.44
      9.74
      7.80
      6.55
      5.53

      17.10
      12.21
      11.79
      6.22
                                 eutrophic species
                                    Page -23-

-------
                                   Table 5
                Seasonal Relative Abundance of Common (>5%)
                        Species in the Central Basin 1979
Cruise

March 27-29
April 17-20

May 15-26
July 11-19
July 31-
  August 4
September 11-21
    Percent of
Total Biovolume

    36.03
    10.81
     8.89
     7.59
     7.32
Species

Stephanodiscus niagarae  •
Fragilaria spp.
Stephanodiscus binderana  •
Unidentified centric diatom
Gyrosigma spp.

No data

Stephanodiscus niagarae  •            15.55
Melosira spp.                        12.29
Tabellaria Fenestrata                 11.26
Diatoma tenue var. elongatum •       10.65
Rhodomonas minuta                  10.47
Unidentified non-green flagellate        7.09
Fragilaria crotonensis                  5.99

Ceratium hirundinella  •              28.53
Coelastrum retic ulatum               14.67
Staurastrum paradoxum  •             7.21
Cryptomonas erosa                    5.81
Rhodomonas minuta                   5.53
Oocystis borgei  •                     5.08

Represents only the western portion
 of the basin
Ceratium hirundinella  •              25.30
Aphanizomenon flos-aquae  •         22.98
Fragilaria crotonensis                 19.28
Coscinodiscus rothii  •                8.19

Stephanodiscus niagarae  •            28.05
Aphanizomenon flos-aquae  •          8.36
Pediastrum simplex •                 7.39
Ceratium hirundinella  •               7.28
                              eutrophic species

                                    Page -24-

-------
                            Table 5 (Continued)
Cruise

October 4-10



November 7-16
Species

Stephanodiscus niagarae  •
Melosira spp.
Aphanizomenon flos-aquae

Melosira spp.
Stephanodiscus niagarae  •
Stephanodiscus binderana  '
   Percent of
Total Biovolume

   30.63
   18.40
     8.23

   41.76
   29.97
   14.69
                             eutrophic species
                                   Page -25-

-------
                                   Table 6
                Seasonal Relative Abundance of Common (>5%)
                       Species in the Eastern Basin -1978
Cruise

May 18-25
June 6-15
June 23 - July 2
July 19-29
August 8-16
August 29 -
 September 6
Species

Stephanodiscus binderana
Asterionella Formosa
Melosira spp.
Stephanodiscus niagarae  •
Fragilaria crotonensis

Unidentified pennate
Cryptomonas erosa
Tabellaria fenestrata
Closterium lunula

Cryptomonas erosa
Fragilaria crotonensis
Rhodomonus minuta
Unidentified flagellate
Asterionella formosa
Tabellaria fenestrata

Anabaena flos-aquae •
Oocystsi borgei  •
Ceratium hirundinella •
Staurastrum paradoxum  •
Cryptomonas ovata

Scenedesmus bijuga  •
Oocystis borgei  •
Ceratium hirundinella •
Unidentified coccoid green

Oocystis borgei  •
Oocystis sp.  •
Scenedesmus bijuga  •
Unidentified coccoid green
    Percent of
Total Biovolume

       20.45
       17.8
        9.6
        9.6
        9.2

       15.7
       14.0
       11.5
        5.3

       16.4
       14.4
       11.7
       11.2
        9.8
        6.6

       18.7
       17.0
       13.0
        7.4
        5.1

       28.4
       15.1
        8.3
        5.5

       24.9
       16.7
       11.1
        8.0
                                  eutrophic species

                                    Page -26-

-------
                             Table 6 (Continued)
Cruise

October 3-12
October 24 -
 November 1
November 7-16
Species

Oocystis borgei  •
Oocystis sp.
Tabellaria fenestrata
Staurastrum paradoxum  •'
Unidentified coccoid green
Unidentified pennate
Tabellaria fenestrata
Stephanodiscus niagarae
Cryptomonas erosa
Oocystis borgei  •
Cryptomonas ovata
Staurastrum paradoxum

Cryptomonas erosa
Tabellaria fenestrata
Staurastrum paradoxum
Cryptomonas ovata
Cosmarium sp.
    Percent of
Total Biovolume

      13.9
      11.1
      10.4
      8.6
      6.3
      5.8
     21.9
     14.7
     13.3
      7.2
      7.0
      5.1

     18.1
     15.2
     12.8
     10.6
      5.2
                                 eutrophic species

                                   Page -27-

-------
                                  Table 7
                Seasonal Relative Abundance of Common (>5%)
                       Species in the Eastern Basin -1979
Cruise

March 27-29


April  17-20

May 15-26

July 11-19
July 31-
 August 4

September 11-12
October 4-10
Species

Stephanodiscus niagarae  •
Unidentified Centric Diatom

No Data

No Data

Oocystis borgei  •
Ceratium hinrundinella  •
Rhodomonas minuta
Fragilaria crotonensis
Cryptomona erosa
No Data

Ceratium hirundinella  •
Staurastrum paradoxum
Oocystsi spp.
Cosmarium spp.
Coelastrum microporum

Stephanodiscus niagarae
Ceratium hirundinella  •
Microcystis aeruginosa
Staurastrum paradoxum
    Percent of
Total Biovolume

       78.33
        8.17
       19.31
       17.49
       11.06
        7.30
        5.70
       27.78
       10.02
        8.72
        7.50
        6.78

       35.73
       10.54
       10.49
        5.02
November 7-16
Stephanodiscus niagarae
Cryptomonas erosa
       66.87
        5.24
                                 eutrophic species
                                   Page -28-

-------
                                       Table 8

          Mean Epilimnetic Biomass in the Western Basin1 of Lake Erie (mg/1)

                            July - November 1970,21978,1979

                           1970                     5.18
                           1978                     2.48
                           1979                     7.70 (4.91)3

1)     1978 and 1979 mean for stations 50, 51, 55, 58 and 61 which correspond to those surveyed in
       1970.

2)     1970 data from Munawar and Munawar 1976.

3)     Mean biomass not including the large bloom observed on the November 11, 1979 cruise.
                                        Page-29-

-------
                                     Table 9
                  Mean Monthly Precipitation at Toledo, Ohio and
                  Tributary Phosphorus Load to the Western Basin

                               Precipitation (inches)
Difference
Month
January
February
March
April
May
June
July
August
September
October
November
December
1978
3.14
0.54
2.34
3.74
2.48
5.34
1.86
1.67
3.19
1.65
2.48
3.31
1979
1.24
0.70
2.55
4.03
3.15
4.23
3.96
4.71
2.90
2.02
4.25
2.46
30 year
(1979-1978
-1.90
0.16
0.21
0.29
0.67
-1.11
2.10
3.04
-0.29
0.37
1.77
-0.85

Normal
2.08
1.75
2.52
2.95
3.33
3.38
3.23
3.07
2.40
2.24
2.32
2.24
Month
                     Tributary Phosphorus Loads (Metric Tons)
                               to the Western Basin
Total Phosphorus

1978         1979
January
February
March
April
May
June
July
August
September
October
November
December
562
474
2099
1605
679
573
588
517
506
527
514
506
496
411
1245
1279
642
468
530
584
438
434
626
982
Orthophosphorous

1978

255
210
676
580
315
254
266
231
228
239
233
255
1979

259
225
522
539
315
251
284
304
234
235
301
414
                                     Page -30-

-------
           Figure 1
                                                    NEW YORK
    CLEVELAND
                                    PENNSYLVANIA
OHIO
     FIGURE 1
SAMPLING LOCATIONS
       1978
            Page-31-

-------
          Figure 2
                                                 NEW YORK
    CLEVELAND
                                  PENNSYLVANIA
OHIO
    FIGURE 2
SAMPLING LOCATIONS
      1979
        Page -32-

-------
                                     Figure 3


                Seasonal Fluctuation in Total Phytoplankton Biomass
                     in the Western Basin of Lake Erie in -1978
•S
 r*
"r*.

Jr
    IG.o


    is.fl


    T4.0

    13-0


    12.0


    n,o


     IO.O


      9.fl

      DJO
      3.O


      2.D
                                                                                  u
                                                                                  a
j^t I Fab ~"[~tf or I A>»» | May | Jime j jjtj T| ftun
                                                             Pel
                                    Page -33-

-------
                    Figure 4

Seasonal Fluctuation in the Major Group Composition
  of the Phytoplankton in the Western Basin in 1978
 Cyanophyta

 , Chlorophyta


 Diatomeae
Cryptomonadinae

Dinophycinae


Unidentified Flagellate
                     Page -34-

-------
                           Figure 5

         Seasonal Variation in the Diatomeae, Chlorophyta,
            and Cyanophyta in the Western Basin -1978
                                                  *.*
i.eo
                                                 gCI'T |  QCT | MOV l| PEC
                            Page -35-

-------
                            Figure 6

     Seasonal Variation in the Dinophycinae, Chrysomonadinae,
         and Cryptomonadinae in the Western Basin -1978
                                  4.0
                IAPR I MAY TJuNE | ju~v| "Joi [septIOCT I NOW  DEC
C hrysomorMHl iJiiva « • * • mm u m • •
                          Page -36-

-------
                                      Figure 7
                   Seasonal Fluctuation in the Total Phytoplankton
                  Biomass in the Central Basin of Lake Erie in -1978
o
03
17.0

16.0

15.0

14.0

13.0

12.0


11.0

10.0

 9.0

 8.0

 7.0

 6.0

 5.0

 4.0

 3.0


 2.0

  1.0

 0.0
           Jan I  Feb
                 Mar  I April | May
June I July
Aug  Sep   Oct   Nov {Dec
                                    Page -37-

-------
                                     Figure 8

                 Seasonal Fluctuation in the Major Group Composition
                    of the Phytoplankton in the Central Basin in 1978
100   B—
          JAN   FEB  MAR  APB  MAY
Cyanophyta

Chlorophyta

Diatomeae
                                                       Cryptomonadinae

                                                       Dinophycinae

                                                       Unidentified Flagellate
                                       Page -38-

-------
                                 Figure 9

              Seasonal Variation in the Diatomeae, Chlorophyta,
                 and Cyanophyta in the Central Basin -1978
                                2.4
I
s
1.60


1.5O



1.4O


  30


1.2O



1.10


1.OO



0.90


O.80


0.70


O.60


O.BO


0.40


O.3O


O.20



0.10


O.OO
          JAN  FEB  MAR APR  MAY JUNE  JULY  AUG  SEPT   OCT  NOV  DEC
        Cyanophyta ••
        Chlorophyta ••
        Diatomeae  ^•jt
                                Page -39-

-------
                               Figure 10

         Seasonal Variation in the Dinophycinae, Chrysomonadinae,
              and Cryptomonadinae in the Central Basin -1978
    1.6O


    1.SO


    1.40


    1.30


    1-.2O


    1.10


    1.OO


    O.9O


    0.8O
S  0.70
    0.30


    O.20


    O.1O


    O.OO
         JAN   FEB  1 MAR APR 1 MAY JUNE JULY AUG  SEPT  OCT  NOV  DEC
        Dinophycinae
        Chrysomonadinae !•••••••••
        Cryptomonadinae v^^'W.'ur'
                               Page -40-

-------
                                   Figure 11



                  Seasonal Fluctuation in the Total Phytoplankton

                 Biomass in the Eastern Basin of Lake Erie in 1978
E
o

2
17.0



15.0



15.0



14.0



13.0




12.0




11.0




10.0



 9.0




 8.0




 7.0



 6.0




 5.0




 4.0



 3.0




 2.0



 1.0




 0.0
           Jan   Feb   Mar  April I May  June  July  Augl Sep  Oct  | New [ Dec
                                    Page-41-

-------
                    Figure 12

 Seasonal Fluctuation in the Major Group Composition
   of the Phytoplankton in the Eastern Basin in -1978
	1	1	1	^r,p»rrn^i
FEO I M1AR | ARH | J.
-------
                               Figure 13


          Seasonal Variation in the Diatomeae, Chlorophyta, and
                  Cyanophyta in the Eastern Basin • 1978
                                  1.8
r

x,
o>
    1.6O



    1.50



    1.4O



    1.30



    1.20



    1.10



    1.OO



    0.30



    O.8O
5  0.70



   O.6O



   O.5O



   0.40



   O.30



   O.2O



   O.1O



   0.00
          JAN   FEB  MAR  APR  MAY  JUNE  JULY AUG  SEPT  OCT | NOV  DEC
        Cyanophyta  mmmaaBffmaaBmm
        Chlorophyta  •••••••••••••
        Diatomeae   jrjr*r*r*'*rJ
                                Page -43-

-------
                      Figure 14

Seasonal Variation in the Dinophycinae, Chrysomonadinae,
     and Cryptomonadinae in the Eastern Basin -1978
1.6O
1.5O
1.40
1.3O
1.20
1.1O
1.OO
" 0.90
en
« 0.8O
(0
6
.2 0.70
CO
0.6O
0.50
O.40
0.30
0.20
O.10
0.00

— 	
_ 	
_ 	
_ —
_ —
_ —
— —

-•— • . "~~


— 	

— —
; A ^_ ;
JAN | FEB | MAP | APR j MAY JJUNE | JULYJ AUG | SEPT | OCT | NOV | DEC

Dinophycinae
Chrysomonadinae ••••••••••
Cryptomonadinae rjrjr^rjrjrjrjr
                       Page -44-

-------
                                  Figure 15


           Seasonal Fluctuation in the Total Phytoplankton Biomass'
                  in the Western Basin of Lake Erie in -1979
 y,
 n

 o
m
Q.

a
17.0,
    I

16,0


15.0


14.0


13.0.1


12.0



11.0



10.0


 9.0


 8.0


 7.0


 6.0


 5.0



 4,0


 3.0



 2.0


 1.0



 0.0
           Jan
           Feb
Mir
April
Msy |June | July | Aup | Sep
Del | Nov
                                                                Die
                                   Page-45-

-------
                    Figure 16

Seasonal Fluctuation in the Major Group Composition of
    the Phytoplankton in the Western Basin in -1979
          Diatomeae
Cryptomonadinae

Dinophycinae

Unidentified Flagellate
                      Page -46-

-------
                                Figure 17

             Seasonal Fluctuation in the Diatomeae, Chlorophyta,
                 and Cyanophyta in the Western Basin -1979
                           2.O6
 1.60


 1.50


 1.4O


 1.3O


 1.20


 1.1O


 1.OO


O.90


0.80
•9   0.70
CO
    O.6O


    o.so


    O.4O


    0.3O


    0.20
^
O)
          JAN | FEB 1 MAR | APR | MAY JJUNE | JULYJ AUG | SEPT | OCT | NOV |  DEC
        Cyanophyta  ••••••••••••••i
        Chlorophyta  •••••••••••••
        Diatomeae  ^^jr^^jr^r*^
                                Page -47-

-------
                            Figure 18

     Seasonal Variation in the Dinophycinae, Chrysomonadinae,
          and Cryptomonadinae in the Western Basin -1979
1.5O


1.4O


1.30


1.20



1.10


1.OQ


O.90
O.6O


O.5O


O.1O


0.30


0.2O


O.1O
      JAN   FED  MAR APR  I MAY JUNE JULY  AUG SEPT  OCT  NOy  DEC
    Dinophycinae
    Chrysomonadinae !•••••••••
    Cryptomonadinae •jr**rjr^*r^jr
                           Page -48-

-------
                                 Figure 19

            Seasonal Fluctuation in the Total Phytoplankton Biomass
                   in the Central Basin of Lake Erie in -1979
^o
5
          \Jan  Feb  Mar 1 April  May  June  July  Aug 1 Sep  dot I Nov   Dec
     0.0
                                  Page -49-

-------
                          Figure 20
       Seasonal Fluctuation in the Major Group Composition
         of the Phytoplankton in the Central Basin in -1979
JAM 1 FEB  ! MAW 1 APR  I MAY lJUNE [JULY
        Cyanophyta
        i
        Chlorophyta

        Diatomeae
Cryptomonadinae

Dinophycinae

Unidentified Flagellate
                          Page -50-

-------
E
o
    1.00




    i.so





    1.4Q




    1.30





    1.20





    1.10





    1.OO





    0.90
    0.60





    O.50






    O.4O





    O.3O





    O.20






    o.io





    0.00
                                 Figure 21



              Seasonal Variation in the Diatomeae, Chlorophyta,

                  and Cyanophyta in the Central Basin -1979
2.1



\
                                                   22 X





                                              i
                                                                   ,X'7
                                                                         .6
                 I    J — 'tf

                 % /      S,
JAN  FEB
         MAV I JUN£ | JUtr
                                                        SEPT  OCT   IOOV
        Cynnophyta
        Diatornooo   ^&^if*r4f!*K4r*t*r
                                Page-51-

-------
                           Figure 22

      Seasonal Variation in the Dinophycinae, Chrysomonadinae,
           and Cryptomonadinae in the Central Basin -1979
            FED I MAR I APft  MAY IJUNE I JULY | AUG
O.OO
     Dinophycinae
     ChrysomonBdinae
                             Page -52-

-------
                                    Figure 23


              Seasonal Fluctuation in the total Phytoplankton Biomass
                     in the Eastern Basin of Lake Erie in -1979
o
S
    17.0


    16.0


    15.0


    14.0
    12.UB-
11.0


10.0


 9.0


 8.0


 7.0


 6.0


 5.0


 4.0


 3.0



 2.0


  1.0
      0.0
            Jan   Feb  Mar  April I May |June |  July | Aujj
                                                  Sep
Oct
                                                             Nov
                                                                  Dec
                                    Page -53-

-------
                           Figure 24


      Seasonal Fluctuation in the Major Group Composition of
           the Phytoplankton in the Eastern Basin in 1979
JAN  j FEE  | MAR I APR I MAY I.JUNE
         Cyanophyta

        i
         Chlorophyta



         Diatomeae
Cryptomonadinae


Dinophycinae



Unidentified Flagellate
                           Page -54-

-------
                               Figure 25



             Seasonal Variation in the Diatomeae. Chlorophyta,

                and Cyanophyta in the Eastern Basin -1979
E
-^
en
O

£
          JAN I FEB |"MAR | APR  | MAY [JUNE | JULY AUG | SEPT |  OCT | MOV | DEC
    0.20  —
    0.10  —
        Cyanophyta
        Clorophyta  •••«•

        Diatomeae  ^i*o*o*ur^ur^o«c<
                                Page -55-

-------
                                  Figure 26
            Seasonal Variation in the Dinophycinae, Chrysomonadinae,
                 and Cryptomonadinae in the Eastern Basin -1979
*•*.
 o>
    v&o

    1.BO


    1.4O

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    000
          JAN I FEB | MAR \ APR. [ MAY
                                            JULVl  AUO
[ 5EPT I DCT I NOVJ PEC
        DmopKycinae
        Chrysomonadlrieo  ••*•••••
        Cryptomonadlnae  "fjfjffjtrjf^f^
                                   Page -56-

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                                     Figure 27

Seasonal Variation in the Horizontal Distribution of Total Phytoplankton Biomass in the
                        Epilimnetic Waters of Lake Erie -1978
                                               -  *».- •

                                                   r^
    fj     —"="• •—»• *.-...
_/*3  .-,-.  '•* '•""•.V-.'.^r
                                               /A-j
                                           Seasonal Variation
                                           in the Horizontal Distribution
                                           of Total Phytoplankton Biomass
                                           in the Epilimnetic Waters
                                           of Lake Erie-1978
                                           Data represents means for e)l samples
                                           (rom 1-15 meters.
                                           Sample date is cruise midpoint.
                                                                     g/m>
                                            < 2  2-S 5-1O   1O-2O  >2O
                                     Page -57-

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                                     Figure 28

Seasonal Variation in the Horizontal Distribution of Total Phytoplankton Biomass -1979
                                                       " "/ ' c......
                                                                    t  . •-o~1

                                                                    '"
                                                               •    - •
                                                                  *    ;   f'**?1!!
                                                               f • i__  ' MwiuriwA*;*
                                            Seasonal Variation
                                            In the Horizontal Distribution

                                            of Total Phytoplankton Biomass -1979

                                            Data represents means (or all samples
                                            from 1-15 meters.
                                            Sample date is cruise midpoint.

                                              •   •    •    ©   ^^

                                            <2  2-5 5-10  10-20  >20
                                      Page -58-

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                           Figure 29

         Mean Epilimnetic Biomass in the Western Basin
               of Lake Erie in 1970,1978 and 1979
                                                            IB.ao
i.eo
t.so
1.40
1-3O

1,80

1.10

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en
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JAN 1 FEB j MAR j APR | MAY j JUNE | JULY |


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1979 ittmmttmmmmmmmmm
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f*pr*i«ni tUniEnr Qtoeraptlte erens
fo Mh*t sampled In 197O.
197D DpIB from Mtlrfl»w»r and MunBW»r, 1976.
                          Page -59-

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