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A factory drains its waste water into the nearby lake. It has caused algal bloom.

(a) How was the algal bloom caused?

(b) What would be the consequences?

(c) Name the phenomenon that caused it.


(a) Algal bloom was caused due to increased concentrations of phosphates 

and nitrates from industries, residential wastes, sewage as well as from 

agricultural run off water into the water bodies result in excessive growth

of algae which form a mat on the surface of water.

(b) It results in depletion of dissolved oxygen resulting in death of aquatic life.

It also decreses light penetration thus affecting photosynthesis.

(c) The phenomenon that caused it is eutrophication. Some bloom from algae are

extremelly toxic to human beings and animals.