The present study was carried out in the Uppanar River (Cuddalore Coast) from September 2015 to August 2016. The samples were collected during morning hours and were analysed monthly for physical, chemical and biological parameters. The various physico-chemical parameters like Water temperature, pH, Dissolved Oxygen, inorganic nitrate, inorganic nitrite, inorganic phosphate, and reactive silicate were analyzed. Results have shown an increased concentration in physico-chemical parameters is more in summer compared to other seasons. In this study phytoplankton diversity were noticed that, total of 58 species of phytoplankton were identified from the two study sites of Uppanar river during the study period. Out of 58 species, 34 species belonged to Bacillariophyceae (diatoms), 13 species to Dinophyceae (Dinoflagellates), 6 species to Cyanophyceae (Blue-greens), 4 species to Chlorophyceae (Green) and 1 species to Chrysophyceae (Silicoflagellates).
