Coccolithophore
unicellular algae responsible for the formation of chalk
Coccolithophores, or coccolithophorids, are single-celled organisms which are part of the phytoplankton, the autotrophic (self-feeding) component of the plankton community. They form a group of a few hundred species, and belong either to the kingdom Protista, according to Robert Whittaker's five-kingdom system, or clade Hacrobia, according to a newer biological classification system. Within the Hacrobia, the coccolithophores are in the phylum or division Haptophyta, class Prymnesiophyceae (or Coccolithophyceae). Coccolithophores are almost exclusively marine, are photosynthetic and mixotrophic, and exist in large numbers throughout the sunlight zone of the ocean.
Coccolithophores are the most productive calcifying organisms on the planet, covering themselves with a calcium carbonate shell called a coccosphere. It is formed when a cell arrange a series of interlocking coccoliths to completely cover its surface. Coccoliths (minute calcium carbonate platelets) are generated within the cell, suggesting that the cell diameter cannot be exceeded by the maximum coccolith size. In addition, coccolith size and the orientation of calcite crystals forming coccoliths can vary among species. Although the interlocking structure of coccoliths offers strong mechanical protection for cell, the specific topology of the coccoliths (the way they interconnect within the coccosphere) and the mechanisms governing their arrangement remain unclear. One key function may be that the coccosphere offers protection against microzooplankton predation, which is one of the main causes of phytoplankton death in the ocean.
“Coccolithophore” enters the record as unicellular algae responsible for the formation of chalk. Crown Archives preserves that source wording while asking what Coccolithophore, unicellular and algae can confirm, complicate or overturn.
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This entry incorporates text from “Coccolithophore” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.