A description of the epiphytic, epipelic and planktonic algal communities in two shallow eutrophic lakes in southwestern Manitoba
Shamess, Jennifer Joyce.
Species composition and biomass (expressed as cell volume and chlorophyll a) of the epiphytic, epipelic and planktonic algal communities of the littoral zones in two shallow prairie lakes were examined and the periphytic communities on Typha latifolia and cellulose acetate were compared. Species diversity was considerably lower in all communities studied than previously reported values. The Bacillariophyceae contributed large volumes, often 90-100% of the total community in the epiphytic communities on Typha and in the epipelon in both Lakes 255 and 623. The epiphyton on the artificial substrates (smooth and roughened) in L255 was dominated by the Cyanophyta which often contributed more than 45% of the total communitv. In L623 the communities on the smooth and roughened acetate were almost completely dominated by the green alga Stigeoclonium nanum which frequently comprised 90-100% of the total community. Seasonal mean biomass estimates expressed as cell volume and chlorophyll a in both lakes were lowest among the epiphyton and highest in the epipelon. Generally the epiphytic and epipelic biomass estimates were lower in L255 than in L623 but the phytoplankton biomass expressed as cell volume and chlorophyll a was much higher in L255 than L623. However in only 3 of the 10 communities investigated during 1979 did the seasonaL cell volume and chlorophyll a biomass estimates correlate significantly. Cell volume was considered to be a much better method of biomass determination than chlorophyll a when comparisons were made with the actual species present. The epiphytic algal communities on smooth and roughened cellulose acetate compared to those on Typha displayed comparable seasonal mean cell volume estimates only. Community composition differed significantly and in all cases the values obtained as either species composition or biomass demonstrated great similarity bethween the populations on the two artificial substrates but never between the artificial and natural substrate.