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Zooplankton are the heterotrophic (sometimes detritivorous) type of plankton. Plankton are organisms drifting in the water column of oceans, seas, and bodies of fresh water. The name of zooplankton is derived from the Greek zoon (ζῴον), meaning "animal", and planktos (πλαγκτος), meaning "wanderer" or "drifter".1 Many zooplankton are too small to be seen individually with the naked eye.
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Ecology
Zooplankton is a broad categorisation spanning a range of organism sizes that includes both small protozoans and large metazoans. It includes holoplanktonic organisms whose complete life cycle lies within the plankton, and meroplanktonic organisms that spend part of their life cycle in the plankton before graduating to either the nekton or a sessile, benthic existence. Although zooplankton are primarily transported by ambient water currents, many have some power of locomotion and use this to avoid predators (as in diel vertical migration) or to increase prey encounter rate.
Ecologically important protozoan zooplankton groups include the foraminiferans, radiolarians and dinoflagellates (the latter are often mixotrophic). Important metazoan zooplankton include cnidarians such as jellyfish and the Portuguese Man o' War; crustaceans such as copepods and krill; chaetognaths (arrow worms); molluscs such as pteropods; and chordates such as salps and juvenile fish. This wide phylogenetic range includes a similarly wide range in feeding behavior: filter feeding, predation and symbiosis with autotrophic phytoplankton as seen in corals. Zooplankton feed on bacterioplankton, phytoplankton, other zooplankton (sometimes cannibalistically), detritus (or marine snow) and even nektonic organisms. As a result, zooplankton are primarily found in surface waters where food resources (phytoplankton or other zooplankton) are most abundant.
Through their consumption and processing of phytoplankton (and other food sources), zooplankton play an important role in aquatic food webs, both as a resource for consumers on higher trophic levels (including fish), and as a conduit for packaging the organic material in the biological pump. Since they are typically of small size, zooplankton can respond relatively rapidly to increases in phytoplankton abundance, for instance, during the spring bloom.
Aside from this role in aquatic food webs, zooplankton can also act as an important disease reservoir. They have been found to house the bacterium Vibrio cholerae, causative agent of cholera, by allowing the cholera vibrios to attach to their chitinous exoskeletons. This symbiotic relationship greatly enhances the bacterium's ability to survive in an aquatic environment, as the exoskeleton provides the bacterium with an abundant source of carbon and nitrogen.2
See also
- Bacterioplankton
- Biological pump
- Diel vertical migration
- Gelatinous zooplankton
- Iron fertilization
- Ocean acidification
- Phytoplankton
- Plankton
- Primary production
References
- ^ Thurman, H. V. (1997). Introductory Oceanography. New Jersey, USA: Prentice Hall College. ISBN 0132620723.
- ^ Jude, B.A., Kirn, T.J., Taylor R.K. (2005). "A colonization factor links Vibrio cholerae environmental survival and human infection". Nature 438: 863–6.
External links
- Plankton*Net @ Roscoff, images of planktonic species
- Guide to the marine zooplankton of south eastern Australia, Tasmanian Aquaculture and Fisheries Institute
- Australian Continuous Plankton Recorder Project
Wikipedia content modification information:
- This page was last modified on 1 January 2009, at 08:45.
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