A large number of fish are suddenly found floating dead on a lake.
A large number of fish are suddenly found floating dead on a lake. There is no evidence of toxic dumping by you find an abundance of phytoplankton, suggest a reason for the fish kill.
3 Answers
The amount of dissolved oxygen present in water is limited. The abundance of phytoplankton causes depletion of this dissolved oxygen. This is because phytoplankton’s are degraded by bacteria present in water. For their decomposition, they require a large amount of oxygen. Hence, they consume the oxygen dissolved in water. As a result, the BOD level of water drops below 6ppm, inhibiting the growth of fish and causing excessive fish kill.
The amount of dissolved oxygen present in water is limited. The abundance of phytoplankton causes depletion of this dissolved oxygen. This is because phytoplanktons are degraded by bacteria present in water. For their decomposition, they require a large amount of oxygen. hence, they consume the oxygen dissolved in water. As a result, the BOD level of water drops below 6 ppm, inhibiting the growth of fish and causing excessive fish kill.
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 ppm) which gets is further depleted. When the level of dissolved oxygen falls below 6 ppm, the fish cannot survive. Hence, they die and oat dead in water.