In a village in Karnatka, people started cultivating crops all around a lake which was always filled with water. They added fertilisers 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. Analyse the situation and give reasons for excessive growth of plants and death of fish in the lake.

Explanation

As many fertilisers contain phosphates and nitrates, the water body bacome enriched with these chemicals. This enriches the nutrients in water leading to excessive growth of small, green, aquatic plants and the surface of water was completely covered with plants (eutrophication). These small plants consume most of the dissolved oxygen of the water leading to its deficiency. Due to this, the fishes and the other aquatic life in the lake die because of oxygen starvation and depletion of light.