Photosynthesis–irradiance responses in the Ross Sea, Antarctica: a meta-analysis

Abstract

Abstract. A meta-analysis of photosynthesis/irradiance measurements was completed using data from the Ross Sea, Antarctica. A total of 544 independent measurements were included. PsB, the maximum, chlorophyll-specific, irradiance-saturated rate of photosynthesis, averaged 1.07 ± 0.060 μg C (μg chl)-1 h-1. Light-limited photosynthetic rates (α) averaged 0.03 ± 0.023 μg C (μg chl)-1 h-1 μmol photons m-2 s-1)-1. Significant variations in PsB and α were found as a function of season, with spring maximum photosynthetic rates being 59% greater than those in summer. Similarly, α values were 48% greater in spring. There was no detectable effect of space on the photosynthetic parameters, and temperature and macronutrient (NO3) concentrations also did not exert a strong influence. However, irradiance, dissolved iron concentrations, and carbon dioxide concentrations when altered under controlled conditions exerted significant influences on photosynthetic parameters. Specifically, reduced irradiance resulted in decreased PsB and α values, whereas reduced iron concentrations were associated with increased PsB and α values. Increased CO2 concentrations also resulted in significantly increased PsB and α values. No significant difference was detected between stations dominated by diatoms and those dominated by the haptophyte Phaeocystis antarctica. The meta-analysis generally confirms the photosynthetic rates predicted from global analyses that are based solely on temperature and irradiance availability, but suggests that for more accurate predictions of the productivity of polar systems a more detailed model that includes temporal effects of photosynthetic parameters will be required.