In the present study, water samples from 1 station of Kolar river were analysed for seasonal fluctuation of physico-chemical parameters i.e., temperature, DO, BOD, total hardness, pH, alkalinity, TDS and. Effect of physico-chemical parameters on surface water density of rotifers was also studied. During one year study 13 species of rotifers were recognised from June 2011 to May 2012.Maximum population density belongs to Branchionus species. The higher concentration of rotifers was found during winter season and minimum during rainy season. An inverse relationship between the population density rotifer and the water current as well as direct relationship between the water temperature and the population density of rotifers was observed in sampling station throughout the study period.
