Plankton

Plankton is the name given to all the microorganisms that drift and hover in the ocean and freshwater. The name comes from the Greek language <math>\pi\lambda\alpha\gamma\kappa\tau o\nu</math> - term for "wanderer" or "drifter". If the organism has a method of propulsion, it is instead called nekton.

Plankton are divided into two classes:

• Phytoplankton (Greek phyto, "plant") are small algae and fungi. They obtain energy by photosynthesis, and live mostly on near the water surface because they need light to survive.
• Zooplankton (Greek zoo: "animal") are small protozoa, crustaceans, copepods, krill, etc. and the eggs and larvae from larger animals.

Plankton concentration and distribution is very sensitive to chemical and physical changes in the sea water.

See also larger images (http://www.ecoscope.com/ocean/index.htm); (photomontage by Uwe Kils)	Hyperiid amphipod, Hyperia macrocephala (http://www.ecoscope.com/hyperia/index.htm) (Uwe Kils)
	Copepod (Calanoida) (Uwe Kils)

See also: algal bloom, domoic acid