Eutrophication of water bodies leading to killing of fishes is mainly due to non-availability of

Eutrophication of water bodies leading to the killing of fishes is mainly due to the non-availability of oxygen. Eutrophication is the aging of a lake by nutrient enrichment of its water. The prime contaminants are nitrates and phosphates (from sewage and industrial effluents), which act as plant nutrients. They overstimulate the growth of algae, causing unsightly scum and unpleasant odours, and robbing the water of dissolved oxygen vital to other aquatic life. Other pollutants flowing into a lake may poison whole populations of fish, whose decomposing remains further deplete the water’s dissolved oxygen content. In such a fashion, a lake can literally choke to death.