Large-scale changes in surface ocean chemical equilibira and elemental cycling have occurred in the fremework of "global change" and are expected to continue and intensify in the future. The progressive increase in atmospheric CO2 affects the marinebiospehere in varous ways: indeirectly, for instance, through rising mean global temperatures causing incereased surface ocean stratification and hence mixed layer insulation, and directly through changes in seawater carbonate chemistry. In lab experimetns we recently observed that CO2-related changes in seawater carbonate chemistry strongly affect calcification of marine coccolithophorids. A rise in atmospheric CO2 may slow down biogenic calcification in the surface ocean with likeley effects on the vertical transport of calcium carbonate to the deep sea. The lab findings will be tested with natural phytoplankton in semi-controlled conditions in a series of floating mesocosms.
University of Bergen, Norway University of Liege, Belgium Observatoire Océanologique, Villefranche-sur-mer, France