SPATIAL VARIATION IN PHYTOPLANKTON DIVERSITY IN THE SABARMATI RIVER AT

Biological assessment is a useful alternative for rating the ecological quality of aquatic ecosystems since biological communities integrate the environmental effects of water chemistry. Phytoplankton are assem-blages of heterogeneous microscopic algal forms whose movement is more or less dependent upon water currents. To know the nature of species composition of phytoplankton and their significance, the present observations were made for a period of twelve months in the Sabarmati River, Ahmedabad, India from three selected sites, i.e. upstream (site 1), midstream (site 2) and downstream (site 3). The study revealed the occurrence of 48 species of phyto-plankton; among these, 21 species of Chlorophyceae, 13 species of Bacillariophyceae, 11 species of Cyano-phyceae and 3 species of Euglenophyceae were recorded. The algal flora of polluted water bodies showed the dominance of blue green algae and diatoms like Oscillatoria, Anabaena, Microcystis, Navicula, Nitzschia, Synedra, Gomphonema through-out the investigation. Many green algae like Eudorina, Scenedesmus, Stigeoclonium and Ankistrodesmus also occurred abundantly and frequently. Various indices such as Palmer’s, Nygaard’s and Shannon’s biotic indices have been used for the assessment of diversit