UTTAR PRADESH JOURNAL OF ZOOLOGY

Phytoplankton constitute the basal trophic level in both marine and freshwater food webs. As primary producers, they harness solar radiation to generate chemical energy through photosynthesis, thereby supplying essential organic matter and nutrients to a diverse array of aquatic organisms. The study has been carried out on the diversity and distribution of phytoplankton and zooplankton groups for a period of 12 months (February 2023 to January 2024) along the lower reaches of the Krishna River. In view of this, three sampling stations, viz., Satrashala (L1), Wadapally (L2) and Ibrahimpatnam (L3) have been selected. Altogether, a total of 25 phytoplankton species has been identified. Out of which there are 12 species of Chlorophyceae in 5 families, 9 species of Bacillariophyceae in 4 families, 3 species of Cyanophyceae in 2 families and one species of Euglenophyceae in one family. Chlorophyceae was dominant with 11 genera and Bacillariophyceae was the second most common dominant group with 9 genera. Simultaneously, 26 zooplankton species belonging to 6 groups, 12 families and 21 genera were recorded. The zooplankton include 8 species of rotifer, 6 species of cladocera, 5 species of crustacean, 4 species of copepod and 1 species of ostracoda. Seasonal variations showed higher zooplankton abundance during the pre-monsoon and lower during the monsoon, influenced by environmental factors such as temperature, nutrient availability, and water flow rates. The study highlights the interdependence of plankton communities and their role as indicators of water quality, emphasising the need for regular monitoring and conservation of the river ecosystem.