coccolithophoren

Coccolithophores are a group of single-celled marine algae (phytoplankton) belonging to the class Haptophyta. They are characterized by the production of calcareous plates called coccoliths that cover the cell surface. When all coccoliths are present, the cell may appear as a coccosphere. Most coccolithophores are planktonic and inhabit the upper sunlit layer of the oceans, ranging in size from about 2 to 20 micrometers.

They are photosynthetic organisms, using chlorophylls a and c and various accessory pigments to capture light energy. They rely on inorganic carbon dissolved in seawater and contribute substantially to primary production in many marine systems. Reproduction is primarily asexual via cell division, but some species show life-cycle stages that alternate between calcified and non-calcified forms, reflecting haploid and diploid phases; sexual reproduction has been reported in certain species.

Ecologically, coccolithophores play a significant role in the marine carbon cycle. Their calcium carbonate coccoliths contribute to carbon sequestration when particles sink to the seafloor, influencing ocean alkalinity and long-term climate processes. Blooms of these algae can color surface waters and are detectable by satellite imagery due to changes in reflectance.

The fossil record of coccolithophores is extensive, with coccoliths preserved as microfossils dating back to the Late Triassic. Their abundant and well-preserved calcite plates make them important for biostratigraphy and reconstructing past ocean conditions. Their study informs both modern ecology and paleoceanography, including paleoclimatology and the formation of sedimentary deposits such as chalk.