Coccolithophore

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. Coccolithophores are ecologically important, and biogeochemically they play significant roles in the marine biological pump and the carbon cycle. Depending on habitat, they can produce up to 40 percent of the local marine primary production. They are of particular interest to those studying global climate change because, as ocean acidity increases, their coccoliths may become even more important as a carbon sink. Management strategies are being employed to prevent eutrophication-related coccolithophore blooms, as these blooms lead...