Effects of elevated CO2 partial pressure and temperature on the coccolithophore Syracosphaera pulchra

The effects of elevated partial pressure of CO2 (pCO(2)) and temperature on the coccolithophore Syracosphaera pulchra were investigated in isolation and in combination. Both the diploid and the haploid life stages were studied. Batch cultures were grown under 4 conditions: 400 mu atm and 19 degrees C; 400 mu atm and 22 degrees C; 740 mu atm and 19 degrees C; and 740 mu atm and 22 degrees C. The growth rate (mu) significantly increased under elevated pCO(2) only in the haploid stage and showed a different pattern with respect to temperature: it was higher at an elevated temperature in the haploid stage at 400 mu atm whereas it decreased in the diploid stage at 740 mu atm. Increasing both parameters together increased the growth rate by 11 % in the haploid stage only. Elevated pCO(2) had a negative impact on the content of particulate organic carbon (POC), production and cell size in both life stages at 19 degrees C, while no significant effect was observed at 22 degrees C. Increasing temperature significantly increased the content of POC and production in the diploid stage at 740 mu atm, while at 400 mu atm it significantly decreased both the content of POC and production in the haploid stage. A simultaneous increase in pCO(2) and temperature had a negative effect on the content of POC and production in the haploid stage only. Neither the rate of calcification (production of particulate inorganic carbon, PIC) nor the PIC:POC ratio were significantly affected by elevated pCO(2), temperature or their interaction. These results showed a strong interactive effect between pCO(2) and temperature in affecting the physiology of S. pulchra, an effect that was often more pronounced in the haploid life stage. Elevated pCO(2) had a stronger effect than temperature.