Zooplankton

Zooplankton are the animal component of the planktonic community (the "zoo-" prefix comes from ζῷον). Plankton are aquatic organisms that are unable to swim effectively against currents. Consequently, they drift or are carried along by currents in the ocean, or by currents in seas, lakes or rivers. Zooplankton can be contrasted with phytoplankton, which are the plant component of the plankton community (the "phyto-" prefix comes from φῠτόν). Zooplankton are heterotrophic (other-feeding), whereas phytoplankton are autotrophic (self-feeding). In other words, zooplankton cannot manufacture their own food. Rather, they must eat plants or other animals instead. In particular, they eat phytoplankton, which are generally smaller than zooplankton. Most zooplankton are microscopic but some (such as jellyfish) are macroscopic, meaning they can be seen with the naked eye. Many protozoans (single-celled protists that prey on other microscopic life) are zooplankton, including zooflagellates, foraminiferans, radiolarians, some dinoflagellates and marine microanimals. Macroscopic zooplankton include pelagic cnidarians, ctenophores, molluscs, arthropods and tunicates, as well as planktonic arrow worms and bristle worms. The distinction between plants and animals often breaks down in very small organisms. Recent studies of marine microplankton have indicated over half of microscopic plankton are mixotrophs. A mixotroph is an organism that can behave sometimes as though it were a plant and sometimes as though it were an animal, using a mix of autotrophy and heterotrophy. Many marine microzooplankton are mixotrophic, which means they could also be classified as phytoplankton. Zooplankton (ˈzoʊ.əplæŋktən; ˌzoʊ.əˈplæŋktən) are heterotrophic (sometimes detritivorous) plankton. The word zooplankton is derived from ζῷον; and πλᾰγκτός. Zooplankton is a categorization spanning a range of organism sizes including small protozoans and large metazoans.