Question

It is understandable that wastes from houses and industries cause water pollution. But how can fertilizers, which are such useful compounds, cause water pollution?

Answer 1

Fertilizers are introduced into the water bodies through run off caused due to rain. These fertilizers increase the growth of algae in the water, which lowers down the amount of dissolved oxygen in the water. After the death of algae, the decomposers, which further decrease the dissolved oxygen. As a result, the aquatic plants and animals die because of low oxygen.