Spatio-temporal variations in phytoplankton community structure in small water bodies within Lake Victoria basin, Kenya

Abstract

Spatio-temporal variations of phytoplankton, expressed in terms of species composition and diversity collected at various sampling sites in small water bodies (SWBs) within Lake Victoria basin, Kenya, were investigated monthly from November 2010 to June 2011, in relation to selected physical and chemical water quality parameters. Temperature, D.O, TN and TP revealed a significant difference between the dams (p<0.005) unlike pH and BOD₅. These SWBs were built during the pre-independence era and stocked with various species of fish. The dams provide water for both domestic and agricultural use. A total of 1392 phytoplankton species belonging to four families and 20 genera were identified in Kesses dam whereas in Kerita dam, a total of 376 phytoplankton species belonging to four families and 10 genera were identified. In Siaya dams, Yenga dam had three families of phytoplankton; Chlorophyceae, Euglenophyceae and Cyanophyceae with Mauna also recording four families: Chlorophyceae, Bacillariophyceae, Desmidiaceae and Cyanophyceae. All the SWBs generally registered low species diversity with majority of them recording a value of < 2. Seasonal variations in phytoplankton species composition and diversity were significant (P < 0.05) with low species composition and diversity occurring during the dry season, and being maximum following the end of the rainy season from November 2010 to March 2011, suggesting the possible influence of various environmental factors on the SWBs. Overall, water quality seemed to have had effect on the species diversity, dominance and richness of phytoplankton community structure.

Key words: Community structure, small water bodies (SWBs), phytoplankton, species composition and diversity.