Question

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 waterbody was completely covered with green floating plants and fishes started dying in large numbers

Answer 1

• During rains fertlizers used for agriculture spreads to the lakes.
•  Fertilisers contain phosphates and nitrates by which water body became enriched with these chemicals. 
• These chemicals promote excessive growth of aquatic plants and the surface of water was completely covered with plants. 
• (Eutrophication) Depletion of light in the water body and insufficient availability of dissolved oxygen and nutrients resulted in the death of fish.