In a village in Karnataka people started cultivating


In a village in Karnataka people started cultivating crops all around a lake which was always filled with water. They added fertilizers to their field in order

to enhance the yield. Soon they discovered that the water body was completely covered with green floating plants and fishes started dying in large


Analyse the situation and give reasons for excessive growth of plants and death of the fish in the lake.


Fertilizer rich run off from fields must have passed into the lake. It caused nutrient enrichment of lake water. The result is excessive growth of

algae and other aquatic plants which float on the water surface and produce water bloom. Old dead plants produce a lot of organic matter. The

submerged plants are also killed due to shading. BOD of water increases. As more and more oxygen is consumed by decomposers little is left for

respiration of aquatic animals. Therefore, fish begin to die. The phenomenon of nutrient enrichment of water body that causes formation of water

bloom and subsequent killing of aquatic life is called eutrophication.

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