A REVIEW ON THE EFFECT OF SEASONS AND POLLUTION ON PLANKTON DIVERSITY IN INDIAN FRESHWATERS

Plankton diversity serve as a good bio indicator of the overall health status of the water body. In most of the studies, the plankton diversity was found to be higher during pre monsoon and post monsoon seasons with comparison to monsoon season. These fluctuations are dependent on various environmental factors like pH, light, temperature, turbidity, salinity, dissolved oxygen content etc. Plenty of sunlight, temperature and clear water in pre monsoon and post monsoon seasons are significant reasons for plankton abundance. Monsoon season is characterized by inflow of water, nutrients, silt, and the resultant turbid waters will in turn prevent light penetration and affect the productivity of the aquatic ecosystem. During monsoon season, nutrients were washed off to the water bodies resulting in the diversity of planktons. In the review, it was noted that some planktons are sensitive whereas others are tolerant to environmental stress. Phytoplankton belonging to Cyanophyceae, Euglenophyceae, Chlorophyceae, Bacillariophyceae and Myxophyceae are predominantly seen on polluted waters indicating organic load and eutrophication, whereas zooplanktons like rotifers, copepods and calanoids are abundantly seen in most studies. This review deals with the studies done on plankton diversity with respect to degradation of water quality in freshwater bodies of India.