Question

Excessive richness of nutrients in a water body causes fish mortality. Give reasons

Answer 1

Excessive nutrients in a fresh water body cause fish mortality. ... The presence of large amounts of nutrientsin the water bodies lead to excessivegrowth of algae and cause Algal bloom. The algal blood leads to deterioration of the quality of water, reduces dissolved oxygen and the hence leads to fish mortality.

Answer 2

Release of nutrients rich sewage and industrial effluents leads to the introduction of nutrients like nitrogen and phosphorus  and increase in temperature and BOD of the water body causing increased biological activity which further leads in the formation of algal blooms. This reduces the dissolved oxygen in the water body and thus results in fish mortality