Explanation

Inorganic phosphorus and nitrogen are responsible for the growth of algae. In polluted water, amount of these inorganic substances increases due to which algae increases greatly at the surface of water or pond. Extensive increase of these algae is called water bloom. Due to death of these algae their organic matter gets decomposed. This leads to oxygen depletion due to which aquatic animals die. If these activities persist for long time, the pond has more organic matter and less water. This process is called eutrophication.