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Impacts of elevated pCO2 on trace gas emissions in two microalgae: Phaeocystis globosa and Nitzschia closterium
Abstract. The potential impacts of seawater acidification on the concentrations of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), dissolved acrylic acid (AAd), and various volatile halocarbons, including CH3Cl, CHBr3, CH2Br2, CHBr2Cl, CHBrCl2, and CH3I, were examined during a laboratory CO2 perturbation experiment for the microalgae Phaeocystis globosa and Nitzschia closterium. The microalgae were exposed to ambient CO2 conditions (390–540 µatm,) and to projected concentrations for the end of the century (760–1000 µatm, high carbon [HC]). The growth rate of the two species remained unaffected by elevated CO2. Results showed 48% and 37% decline in the DMS concentration normalized to cell density in P. globosa and N. closterium cultures in the HC treatment compared to the ambient treatment. No significant difference was observed for DMSPp and DMSPd in the two microalgae cultures between the two CO2 levels. The mean AAd concentrations in the P. globosa culture showed a 28% decline in the HC treatment. By contrast, the cell-normalized concentrations of AAd in the HC treatment were 45% lower than in the ambient treatment in N. closterium cultures. No CO2-induced effects were observed for CH3Cl, CHBr3, CHBr2Cl, CHBrCl2, and CH3I, except that the mean CH2Br2 concentration in P. globosa showed a 14% decline, and cell-normalized concentrations of CH2Br2 in N. closterium cultures showed a 32% decline in the HC treatment relative to the ambient level. These results showed that the metabolism processes responsible for the production of climate-active gases in phytoplankton may be affected by high CO2 levels. There might be a potential delay in the responses of trace gas emissions to the elevated pCO2.
EN17130 Accepted 29 September 2017
© CSIRO 2017