Question

How does algal bloom destroy the quality of a fresh water body? Explain.

Answer 1

An algal bloom is the phenomenon of excessive growth of planktonic forms in a nutrient rich water body. As the planktonic species multiply on the surface they from a layer that eventually covers the entire surface of the water body. They block sunlight, which does not reach submerged aquatic plants that may have a role in supplying necessary nutrients to other aquatic life forms and keeping the water clean.

Excretory substances released by planktons build up in concentration and pollute the water. Some algal species even release substances that are toxic for other life forms in the water body. Also, due to the high respiratory needs of such a huge concentration of biomass on the surface, the biological oxygen demand (BOD) of the water body increases, causing many of the life forms to die. Their carcasses further contribute to the deterioration of the quality of the water content.