In a village in Karnataka, people started cultivating crops all around a lake which was always filled with water. They added fertilisers to their field 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 the excessive growth of plants and the death of fish in the lake.
Fertilizers mainly contain phosphates and nitrates. Using these fertilizers around the lake, makes the water body enriched with these chemicals. This enhances the supplements in water leading to excessive development of small, green, aquatic plants, and the surface of the water gets completely covered with plants. This process is called eutrophication. It induces excessive growth of algae. These small plants consume most of the dissolved oxygen in the water leading to its deficiency. Due to this, the fish and the other aquatic life in the lake die because of oxygen starvation and depletion of light.