Question

Floating green microorganisms and plants

Answer 1

It occurs by floating algae and seen in newly sunken ponds containing water rich in food.  

They develop like lightning.  

Except that pond water will turn into green mass nasty phenomenon that is growth of oxygen producing plants will stagnate.  

Tiny algae are floating separately in water.  

Their numbers increase explosively and give green colour to water due to which one can't see any fish on the bottom.  

Answer 2

Floating green microorganisms on the water surface of ponds, lakes etc are called zooplanktons
Floating green plants on the water surface of ponds etc are called phytoplanktons.