Seasonal Variation in the Diversity, Species Richness and Composition of the Phytoplankton Assemblages in a Shallow Lake

Abstract

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 (I m 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).