The group of small animal and plant organisms float or drift in massive numbers in fresh or salt water and consist primarily of diatoms, protozoans, small crustaceans, and the eggs and larval stages of larger animals. Many animals are adapted to feed on plankton, especially by filtering the water.
Some plankton may be capable of vertical migration but generally they flow with their surrounding currents. The opposite of plankton are “nekton” – organisms able to swim against the current.
The term plankton is coined by Victor Hensen. It is derived from the Greek word planktos, meaning drifter or wanderer.