How does rising atmospheric CO2 affect marine organisms?

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How Coccolithophorids Respond to Ocean Acidification
Jin, P. Gao, K. and Beardall, J. 2013. Evolutionary responses of a coccolithophorid Gephyrocapsa oceanica to ocean acidification. Evolution 67: 1869-1878.

The authors write that "coccolithophores, as a key group of oceanic primary producers, play a crucial role in the global carbon cycle, not only in terms of photosynthesis but also by producing calcium carbonate in the form of extracellular plates (coccoliths)." In addition, they note that they "are also important in the sulfur cycle in terms of dimethyl-sulphide (DMS) production (Malin and Erst, 1997)," the significance of which is described under the general heading of Dimethyl Sulphide in our Subject Index. And they state that "particulate inorganic carbon (PIC) produced by coccolithophores in the surface ocean sinks to the deep-sea," which phenomenon, known as the carbonate pump, "is a critical part of the global carbon cycle and has a major feedback effect on global climate (Hutchins, 2011)."

What was done
Jin et al. conducted a laboratory experiment where they grew the coccolithophore Gephyrocapsa oceanica for approximately 670 generations in water in equilibrium with both ambient and CO2-enriched (1000 ppm) air, the latter of which treatments reduced the water's pH to a value of 7.8.

What was learned
Very briefly, the three researchers report that "the high CO2-selected cells showed increases in photosynthetic carbon fixation, growth rate, cellular particulate organic carbon (POC) or nitrogen (PON) production, and a decrease in C:N elemental ratio, indicating a greater up-regulation of PON than of POC production under ocean acidification." And they note that these findings are "in good agreement with a recent study in which E. huxleyi positively adapted to increased CO2 levels," citing Lohbeck et al. (2012).

What it means
Jin et al. equally simply state that their data suggest that "the coccolithophorid could adapt to ocean acidification with enhanced assimilations of carbon and nitrogen," becoming even more productive than it is now.

Hutchins, D.A. 2011. Oceanography: forecasting the rain ratio. Nature 476: 41-42.

Lohbeck, K.T., Riebesell, U. and Reusch, T.B.H. 2012. Adaptive evolution of a key phytoplankton species to ocean acidification. Nature Geoscience 5: 346-351.

Malin, G. and Erst, G.O. 1997. Algal production of dimethyl sulfide and its atmospheric role. Journal of Phycology 33: 889-896.

Reviewed 6 November 2013