Question

A large no.of fish are suddenly found suddenly floating dead on lake.There is no evidence of toxic dumping but you can find an abundance of phytoplankton.Suggest a reason why were the dish found dead?

Answer 1

phytoplankton is the crucial source of food for fish if its maximum the fish can die due to overeating

Answer 2

Answer:

Water has limited amount of dissolved oxygen. This oxygen is depleted due to abundance of phytoplanktons. The bacteria that decompose phytoplanktons, require large amount of oxygen. They consume dissolved oxygen. The BOD level of water drops below 6 ppm which inhibits the growth of fish and causes excessive fish kill.