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 numbers. Analyse the situation and give reasons for excessive growth of plants and death of fish in the lake.
Answers
Fertilisers and pesticides were drawn into the water and as they were not biodegradable, the chemicals got accumulated in the trophic level. So as a result the fishes died. This is called biological magnification.
The main reason of the excessive plant growth and the fish deaths is the extreme usage of artificial chemical fertilizers.
Fertilizers are undoubtedly necessary for the harvesting but it will also affect negatively when it is not used in a controlled manner and amount.
In the situation mentioned in the question,the excessive amount of fertilizers contaminated the harvesting soil ,this contamination also contaminated the nearby water bodies.
The excessive plant growth and the fish deaths happened due to this water contamination.
Because,the unwanted plants only grow in dirty water and fishes need clean water for their healthy survival.