Variations in phytoplankton community structure: A case of Baharini reservoir, Eldoret, Kenya

Abstract

Phytoplankton species composition and abundance within water bodies exhibit seasonal variation. The aim of this study was to obtain an overview of the variation of phytoplankton community structure during the rainy and dry seasons, and their implications regarding water quality. Samples were taken from three sampling sites, at two depths during the rainy dry seasons. All physicochemical parameters did not differ significantly (p>0.05) among sampling stations. However, there were significant (p<0.05) seasonal variations. The phytoplankton comprised of 30 species, mainly Chlorophyceae (12 of total species identified), Cyanophyceae (7), Bacillariophyceae (4), Dinophyceae (3) and Euglenophyceae (4). Phytoplankton density values were higher during the dry season than the rainy season (mean value 1 592 cells/L and 2 958 cells/L respectively). Abundance was dominated by Melosira granulate and Microcystis sp. during the rainy and the dry seasons respectively. The species diversity and evenness of phytoplankton varied significantly between seasons. The Shannon-Wiener diversity index ranged from 2.21 to 3.12 and evenness from 0.72 to 0.95. Seasonal variations in the occurrence, abundance and diversity of the phytoplankton community in the reservoir are influenced by the nature of physical and chemical environment.