- the aggregate of passively floating, drifting, or somewhat motile organisms occurring in a body of water, primarily comprising microscopic algae and protozoa.
- the organisms inhabiting the surface layer of a sea or lake, consisting of small drifting plants and animals, such as diatomsCompare nekton
n.1891, from German Plankton (1887), coined by German physiologist Viktor Hensen (1835-1924) from Greek plankton, neuter of planktos “wandering, drifting,” verbal adjective from plazesthai “to wander, drift,” from plazein “to drive astray,” from PIE root *plak- (2) “to strike, hit” (see plague (n.)). Related: Planktonic.
- Small organisms that float or drift in great numbers in bodies of salt or fresh water. Plankton is a primary food source for many animals, and consists of bacteria, protozoans, certain algae, cnidarians, tiny crustaceans such as copepods, and many other organisms. Compare benthos nekton.