Phytoplankton studies in the Nanticoke area of Lake Erie 1969 - 1978
Changes in abundance and seasonal composition of phytoplankton of the Nanticoke area of Lake Erie have been evaluated at eight to thirteen stations from 1969 to 1978. Water clarity, chlorophyll, phosphorus and temperature values were also assessed. These data are reported in three separate reports by Michalski (1972), Hopkins (1975) and Hopkins (1979). Quantitative measurements of phytoplankton were recorded as Areal Standard Units per millilitre (A.S.U. per ml). The mean value for the ten year period is 382 A.S.U. per ml. The lowest annual mean value of 220 A.S.U. per ml occurred in 1969. The highest annual mean value was 634 A.S.U. per ml and occurred in 1978. However, the second highest level was attained in 1970 when an annual mean of 530 A.S.U. per ml was recorded. Statistical trend analyses of the phytoplankton data indicate that there is only a small increase (~4% per annum) with time. Seasonal succession patterns and biomass levels showed fluctuations expressing unimodal, bimodal and even trimodal peaks from station- to-station and year-to-year. Of the four dominant taxa recorded each year, the first three were always Fragilaria, Cryptomonas and Rhodomonas. This is a good indication of the stability of the algal community at Nanticoke. While phytoplankton densities have decreased in the western basin of Lake Erie coincident with decreased phosphorus loadings, there has been a slight increase in phytoplankton densities and only a small decrease in P concentrations in the Nanticoke area of the eastern basin of Lake Erie. Temperature data collected from continuous recorders in the Nanticoke area showed that while temperatures frequently exceed 20°C during the summer months each year, they rarely exceed 25°C. There is no indication that the number of days in which the temperature exceeds 20°C or 25°C is increasing. The long term stability of the phytoplankton community and temperature regime would suggest that heated inputs to Long Point Bay are well assimilated and are not affecting the biomass or species composition of phytoplankton in the study area.
Biological Surveys/Investigations Reports