Coccoliths are the individual plates formed by coccolithophores such as Emiliana huxleyi¹, and arranged around them in a coccosphere. The coccoliths are shed continually in some species during the coccolithophore's lifetime, as well as following the breakup of the coccosphere on death. They sink through the water column to form an important part of the deep-sea sediments (depending on the water depth), where they were first observed by Thomas Huxley and named by him.

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 ².

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

¹Emiliana Huxleyi coccoliths (http://www.soes.soton.ac.uk/staff/tt/eh/coccoliths.html)

²Functions 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/)