Abstract
The correlation of various hydrological factors with the distribution of phytoplankton and bacteria has been studied in Kinjhar Lake, situated 120 km north of Karachi. This lake is highly eutrophic, containing rich concentrations of nutrients, but the temporal distribution of phytoplankton was generally related to the variations of light and temperature. The effects of light and temperature are perhaps modified by nutrients, particularly when nitrogen and phosphorus are present in surprisingly low concentrations. The effect of mechanical disturbances in the artificial lake also has a significant effect on the growth of phytoplankton and indirectly on consumers, especially fishes.