Plankton is the totality billion sedentary small plant and animal organisms that freely drift in the water column and can not, unlike the nekton, to resist the flow of water. To include plankton bacteria living in the water, algae (phytoplankton), protozoa, some coelenterates, mollusks, crustaceans, eggs, and fish larvae, the larvae of various invertebrates (zooplankton).
Some of these organisms, such as algae, always plankton. Others, such as fish, lobsters, are plankton as long as they are in the stage of embryonic development. The offspring of insects, lay the eggs in the water (mosquitoes, dragonflies) is also plankton.
Plankton is food for most other aquatic animals. It is available in both fresh and sea water.
The term "plankton" invited well-known German scientist Victor Hansen in the late nineteenth century. In Greek language the plankton means "wandering" or "free floating".