Response of primary production and calcification to changes of <i>p</i> CO ₂ during experimental blooms of the coccolithophorid <i>Emiliania huxleyi</i>

Abstract

Primary production and calcification in response to different partial pressures of CO 2 ( P CO 2 ) (“glacial,” “present,” and “year 2100” atmospheric CO 2 concentrations) were investigated during a mesocosm bloom dominated by the coccolithophorid Emiliania huxleyi . The day‐to‐day dynamics of net community production (NCP) and net community calcification (NCC) were assessed during the bloom development and decline by monitoring dissolved inorganic carbon (DIC) and total alkalinity (TA), together with oxygen production and 14 C incorporation. When comparing year 2100 with glacial P CO 2 conditions we observed: (1) no conspicuous change of net community productivity (NCP y ); (2) a delay in the onset of calcification by 24 to 48 hours, reducing the duration of the calcifying phase in the course of the bloom; (3) a 40% decrease of NCC; and (4) enhanced loss of organic carbon from the water column. These results suggest a shift in the ratio of organic carbon to calcium carbonate production and vertical flux with rising atmospheric P CO 2 .