Analyse the situation and give reasons for excessive growth of plants and death of fish in the lake.

Solution – the fertilizers used for irrigation had spread into the lake water . The chemicals contained in the fertilizers were mixed with the water body making it to change it colour . This lead to eutrophication , in which there is excessive growth of the aquatic plants and it covered the whole surface of the lake . When the surface of the lake got covered by the aquatic plants then it hampered the natural sunlight to reach the aquatic animals and also the level of dissolved oxygen was reduced . This finally resulted in death of the fishes in the lake .