A large number of fish are suddenly found floating dead on a lake. There is no evidence of toxic dumping but you find an abundance of phytoplankton. Suggest a reason for the fish kill.

Question

A large number of fish are suddenly found floating dead on a lake. There is no evidence of toxic dumping but you find an abundance of phytoplankton. Suggest a reason for the fish kill.,

MARKS App · Accepted Answer

Excessive phytoplankton (organic pollutants such as leaves, grass, trash etc. ) present in water is biodegradable. A large population of bacteria decomposes this organic matter in water. During this process, they consume the oxygen dissolved in water. Water has already limited dissolved oxygen ( $10 \mathrm{ppm})$. Thus, it is further depleted. When the level of dissolved oxygen falls below 6 ppm, the fish cannot survive. Hence, they die and float dead on the lake.

Search any question & find its solution

Looking for more such questions to practice?