Seasonal variation in the diversity, species richness and composition of the phytoplankton assemblages in a shallow lake

The seasonal variations in the diversity, composition and species richness of phytoplankton in a shallow lake (Gici Lake, Turkey) were studied between January 2000 and April 2001. Samples were collected monthly from surface water and deeper (1m depth) stations and species richness and diversity (Shannon-Wiener, H') were measured. Indices were calculated using biovolume. Climatic changes, especially rainfall, mixing conditions, and relative water column stability were found to be important factors affecting the seasonal variation observed.
A total of 109 species, mostly belonging to the Bacillariophyta and Chlorophyta, were identifed. Among the other taxonomic groups were Cyanoprokaryota, Euglenophyta and Xantophyta. Phytoplankton biomass was dominated by diatoms (R-strategists). The summer assemblages develop during strong thermal stability of the water column and low availability of nutrients (S-strategists).