: Eutrophication is the pollution of water bodies resulting from slow, natural, geological, or biological processes such encroachment of vegetation or accumulation of detritus. This is also called as natural eutrophication, which occurs due to reduction of dissolved oxygen resulting from rich growth of algae and other micro-organisms (due to rich in nutrients in lake or water body in which fertilized fields, domestic sewage are the main source). In eutrophic water bodies sudden death of fishes takes place because of oxygen depletion. Such water bodies support the growth of plants like water hyacinth.