EVOLUTIONARY RESPONSES OF A COCCOLITHOPHORID GEPHYROCAPSA OCEANICA TO OCEAN ACIDIFICATION

The ongoing ocean acidification associated with a changing carbonate system may impose profound effects on marine planktonic calcifiers. Here, we show that a coccolithophore, Gephyrocapsa oceanica , evolved in response to an elevated CO 2 concentration of 1000 μatm (pH reduced to 7.8) in a long‐term (∼670 generations) selection experiment. The high CO 2 ‐selected cells showed increases in photosynthetic carbon fixation, growth rate, cellular particulate organic carbon (POC) or nitrogen (PON) production, and a decrease in C:N elemental ratio, indicating a greater upregulation of PON than of POC production under the ocean acidification condition. Cells from the low CO 2 selection process shifted to high CO 2 exposure showed an enhanced cellular POC and PON production rates. Our data suggest that the coccolithophorid could adapt to ocean acidification with enhanced assimilations of carbon and nitrogen but decreased C:N ratios.