[en] Coccolithophores are probably the most important pelagic producers of calcium carbonate and perhaps the most important contributor to contemporary calcium carbonate production. The accumulation in the photic zone of the calcite produced during the blooms of the most common species, Emiliania huxleyi, produces high-reflectance (HR) patches visible from space. In the context of global warming and ocean acidification, there remain some doubts regarding the future of this group and the carbon (C) fluxes associated to coccolithophorid blooms at the global scale.
A multi-year survey of coccolithophorid blooms, from 2002 to 2008, was carried out along the continental margin of the northern Bay of Biscay and focused on pelagic processes. Based on the hydrographic and biogeochemical data obtained during those campaigns and the analysis of satellite images of sea surface temperature, chlorophyll-a concentration and reflectance, we describe the properties of the HR patches in this region and emphasize on the ecological niche of E. huxleyi. This study offered the opportunity to investigate the impact of coccolithophorid blooms on the exchange of carbon dioxide (CO2) at the air-sea interface and the coupling between primary production and calcification in the field, as determined by 14C incorporation. The distribution of transparent exopolymer particles (TEP) was investigated and the production of TEP is proposed as a mechanism for bloom termination, the critical step leading to massive export depth. Supra-lysoclinal dissolution of coccoliths, as supported by the analysis of scanning electron micrographs, will be discussed in combination with the formation of aggregates to provide a scheme of the onset of the coccolithophorid bloom to its decay.
