Biological Evaluation of Pollution

Only a few years back a severe pestilence to fish life was observed in the Lal Dighi (Benoy-Badal-Dinesh Bag) of Calcutta. Investigations revealed that depletion of water in the tank and rotting of the variety of weeds in the water, deteriorated the water quality that is needed for the particular fish life to survive. Our interest in water pollution is centred upon its effect on animal life particularly on human life. So far we the scientists were less concerned about the living condition of aquatic lives in water. Rather we were more concerned whether these aquatic organisms are polluting the water body by their discharges or not so that the physical and chemical condition of water is not changed below usable 'standard'.