Since its origin in the late Pleistocene, Emiliania huxleyi has become ubiquitous in the world's oceans. It is the most abundant living coccolithophore and the most important organism in the transfer of atmospheric carbon dioxide to the ocean sediments. Morphological forms include coccolith-bearing and naked coccoid cells, and scaled flagellates. Only the coccolith-bearing morphotype is readily idnetifiable in natural samples, and all studies to date on the distribution and abundance of the species have been studies of only this morphotype. Comparison to other coccolithophores suggests the motile form is an alternate life cycle stage, but the life cycle of Emilianian hyxleyi remains poorly understood, and its role in bloom dynamics is unknown. Recently developed techniques permit identificaiton and tracking of naked and flagellated Emiliiania huxleyi cells in natural populations and simplify determination of ploidy in cultured cells. The objectives of this research are (1) to compare the abundances and distributions of the flagellated form to that of the coccoid forms in natural populations before, during and after blooms, (2) to estabilish ploidy and the life history, and thus (3) to determine the role of the flagellated form, and of sexual recombination, in bloom dynamics.
