SEASONAL PERIODICITY OF PHYTOPLANKTON AND CHLOROPHYLL CONTENT IN LAKE MANCHAR

Seasonal fluctuations of 16 dominant genera of phytoplankton, belonging to 4 groups, (Cyanophyta, Chlorophyta, Euglenophyta and Bacillariophyta) found in Manchar lake were studied. Genus Anabaena, Chroococcus, Merismopedia, Microcystis and Pediastrum were found dominant during spring and summer months. Oocystis and Scenedesmus were dominant during autumn. In winter, Chloroococcus, Cyclotella, and Oscillatoria were found dominant. Gomphosphaeria was recorded in high density during summer months, while during winter, very small numbers of colonies were observed. Genus Cymbella gradually increased during warmer months, with a peak in July, and then it gradually decreased. During cold months; the population was very low. The peak of Cyclotella was observed in the month of January. Frequency of Cyanophycean species ranged between 60-70%. Chlorophyll content of water varied within 19-40 mu g/l, during the year. These fluctuations are mostly dependant upon environmental factors such as temperature, salinity, nitrates and phosphate in Manchar lake water.