Coccolith
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Coccoliths are individual plates of calcium carbonate formed by coccolithophores (such as Emiliania huxleyi) which are arranged around them in a coccosphere. The coccoliths are either dispersed following death and breakup of the coccosphere, or are shed continually by some species. They sink through the water column to form an important part of the deep-sea sediments (depending on the water depth). Thomas Huxley was the first to observe and name coccoliths in sedimentary samples.
Although coccoliths are energetically expensive to produce, their purpose is unclear. Hypotheseses include defence against grazing by zooplankton or infection by parasites; maintenance of buoyancy; release of carbon dioxide for photosynthesis; and to filter out harmful UV light.
Coccoliths are composed of calcium carbonate as the mineral calcite and are the main constituent of chalk deposits such as the white cliffs of Dover.
External links
- Emiliania huxleyi coccoliths (http://www.soes.soton.ac.uk/staff/tt/eh/coccoliths.html)
- Possible functions of Coccoliths (http://www-ocean.tamu.edu/Quarterdeck/QD5.2/shatto-slowey2.html)
- International Nannoplankton Association site (http://www.nhm.ac.uk/hosted_sites/ina/)