Decreasing marine biogenic calcification: A negative feedback on rising atmospheric pCO(2)

In laboratory experiments with the coccolithophore species Emiliania huxley i and Gephyrocapsa oceanica, the ratio of particulate inorganic carbon (PIC ) to particulate organic carbon (POC) production decreased with increasing CO2 concentration ([CO2]). This was due to both reduced PIC and enhanced PO C production at elevated [CO2]. Carbon dioxide concentrations covered a ran ge from a preindustrial level to a value predicted for 2100 according to a "business as usual" anthropogenic CO2 emission scenario. The laboratory res ults were used to employ a model in which the immediate effect of a decreas e in global marine calcification relative to POC production on the potentia l capacity for oceanic CO2 uptake was simulated. Assuming that overall mari ne biogenic calcification shows a similar response as obtained for E. huxle yi or G. oceanica in the present study, the model reveals a negative feedba ck on increasing atmospheric CO2 concentrations owing to a decrease in the PIC/POC ratio.