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.