Question

in a village in Karnataka people started cultivating crops all around a lake which has always filled with water . thy added fertilisers to their field in order to enhance yield . soon they discovered that the water body was completely filled with green floating plants and fish started dying in a large numbers . Analyse the situations and give reasons for excessive growth of plants and death of the fish in the lake

Answer 1

Since people used excessive fertilizers in the fields, they were carried down to the lake during rains. As many fertilizers contain phosphates and nitrates, the 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 availabilty of dissolved oxygen and nutrients resulted in the death of fish.

Answer 2

The situation in the village Karnataka is an alarming one and it disturbs the ecosystem of the lake. It is because of the excessive use of the fertilizers which contains nitrates and phosphates which leads to the excessive growth of the floating plants and algae that leads to oxygen deficiency for the aquatic animals. The excessive growth of floating plants creates shade and that affects submerged plants.