Analysis of the phytoplankton community structure in relation to environmental factors in the Kenyan waters of Lake Victoria
Lung'ayia, H.B.O. (1996). Analysis of the phytoplankton community structure in relation to environmental factors in the Kenyan waters of Lake Victoria. MSc Thesis. VUB: Brussel. 77 pp.
Species composition, abundance, distribution and diversity of the four major phytoplankton taxa and total phytoplankton biomass were studied in relation to biotic and environmental factors in September 1994 (dry season) and March 1995 (rainy season) respectively, in the Kenyan waters of Lake Victoria. 103 species were recorded. The blue green algae (Cyanophyceae) contributed the largest number of species followed by diatoms (Bacillariophyceae), green algae (Chlorophyceae) and flagellates (Dinophyceae) in that order. A higher number of species occurred during the dry season. The phytoplankton abundance ranged from 248 to 16,440 Ind./ml in the dry season and from 195 to 21,118 Ind./ml in the rainy season. The blue greens were the most abundant and contributed 53 to 99% of the total phytoplankton abundance in the dry season and 48 to 99% in the rainy season. The diatoms were the second most abundant followed by the green algae and the dinoflagellates. Phytoplankton biomass as indicated by chlorophyll-a content, was higher during the dry season than the rainy season. Concentrations of chlorophyll-a of up to 71.5 mg m-3 were recorded in the dry season and from 2 to 17.2 mg m-3 in the rainy season. Species diversity (Simpson's index) was higher during the dry season and varied from 0.04 to 0.28 in the dry season and from 0.04 to 0.37 in the rainy season. The occurrence of phytoplankton species was found to be related to the characteristics of the different localities in the lake. However, the distribution and abundance of the species was significantly influenced by environmental factors. Turbidity was the most influencing factor during the dry season while turbidity, temperature and concentration of silicates were the most important in the rainy season.
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