Algal blooms occur in freshwater bodies as the result of their nutrient enrichment due to natural factors or man's activities. This is called as eutrophication. It hampers the water quality significantly. Algal blooms form a scum over the surface of the lake, cutting off the supply of oxygen between air and the water body. These algae rob the water body of oxygen leading to the death of aquatic life. Death of both these elements further depletes the oxygen level of the freshwater body. Some Blue Green Algae or BGA may also form bloom over the freshwater body, they release neurotoxins that potentially paralyze the fishes and is equally unfit for human consumption.