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Effect of CO2 enrichment on phytoplankton photosynthesis in the North Atlantic sub-tropical gyre

Tilstone, Gavin, Šedivá, Barbora, Tarran, Glen, Kaňa, Radek, Prášil, Ondřej
Progress in oceanography 2017 v.158 pp. 76-89
Miozoa, biomass, carbon dioxide, carbon dioxide enrichment, carbon dioxide fixation, community structure, pH, photosynthesis, phytoplankton, primary productivity, seawater, spectroscopy
The effects of changes in CO2 concentration in seawater on phytoplankton community structure and photosynthesis were studied in the North Atlantic sub-tropical gyre. Three shipboard incubations were conducted for 48h at ∼760ppm CO2 and control (360ppm CO2) from 49°N to 7°N during October and November 2010. Elevated CO2 caused a decrease in pH to ∼7.94 compared to ∼8.27 in the control. During one experiment, the biomass of nano- and picoeukaryotes increased under CO2 enrichment, but primary production decreased relative to the control. In two of the experiments the biomass was dominated by dinoflagellates, and there was a significant increase in the maximum photosynthetic rate (PmB) and light-limited slope of photosynthesis (αB) at CO2 concentrations of 760ppm relative to the controls. 77K emission spectroscopy showed that the higher photosynthetic rates measured under CO2 enrichment increased the connection of reversible photosystem antennae, which resulted in an increase in light harvesting efficiency and carbon fixation.