A review of the coccolithophorid Emiliania huxleyi (Prymnesiophyceae), with particular reference to growth, coccolith formation, and calcification-photosynthesis interactions

Emiliania huxleyi is numerically the most important coccolithophorid in the modem ocean and has been intensely studied in the contexts of biogeochemistry (especially relating to the global carbon cycle), plankton ecology, biomineralization, and cellular carbon transport. This paper reviews older as well as more recently acquired information on reproduction, morphology, ecophysiology, and cell physiology of E. huxleyi, emphasizing aspects that are relevant to coccolith formation and calcification-photosynthesis interactions. The existence of a number of ecotypes, which probably accounts for the wide distribution of this species in nature, complicates comparisons between laboratory studies in which different clones have been used. Coccolith formation is a strongly regulated process; use of mutants may be helpful in elucidating the control mechanisms involved. Conceptual models illustrating the role of calcification in photosynthetic carbon supply are supported by extensive experimental evidence, but the exact mechanisms of calcium and bicarbonate ion transport and of CO2 entry into the cell remain to be established.