How does rising atmospheric CO2 affect marine organisms?

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Respiration of Cold-Water Corals in CO2-Enriched Seawater
Maier, C., Bils, F., Weinbauer, M.G., Watremez, P., Peck, M.A. and Gattuso, J.-P. 2013. Respiration of Mediterranean cold-water corals is not affected by ocean acidification as projected for the end of the century. Biogeosciences 10: 5671-5680.

The authors write that previous experiments examining the effect of ocean acidification on the cold-water corals L. pertusa and M. oculata have indicated that their rates of calcification remain positive even in waters where Ωa is < 1 (Maier et al., 2009; Thresher et al., 2011; Form and Riebesell, 2012)." And they add that Form and Riebesell (2012) and Maier et al. (2012, 2013) have found that "calcification rates of these species remained positive at a partial pressure of CO2 (pCO2) of 1000 ľatm, a value that is at the high end of projected changes by 2100."

What was done
Seeking to determine if these feats of survival by L. pertusa and M. oculata might have been driven by increased respiration rates, Maier et al. measured respiration rates "for both short and long periods of time at pCO2 levels ranging from ambient (350 ľatm) to elevated (1100 ľatm) levels." And they did it using the same experimental setup as a previous study demonstrating that elevated pCO2 had no effect on the rate of calcification in these two species (Maier et al., 2013)."

What was learned
Very simply, the six scientists report that "in the range of pCO2 studied so far, up to 1215 ľatm, no significant change in respiration was found as a function of increasing pCO2."

What it means
As for what "this means," in the words of Maier et al., it is that "for the maintenance of high calcification rates over a large range of pCO2 of up to 1000 ppm, there is no evidence for a direct energy allocation from food uptake to calcification in order to compensate for higher energy required to maintain calcification constant despite a decrease in pH," which is very good news indeed.

Form, A.U. and Riebesell, U. 2012. Acclimation to ocean acidification during long-term CO2 exposure in the cold-water coral Lophelia pertusa. Global Change Biology 18: 843-853.

Maier, C., Hegeman, J., Weinbauer, M.G. and Gattuso, J.-P. 2009. Calcification of the cold-water coral Lophelia pertusa, under ambient and reduced pH. Biogeosciences 6: 1671-1680.

Maier, C., Watremez, P., Taviani, M., Weinbauer, M.G. and Gattuso, J.-P. 2012. Calcification rates and the effect of ocean acidification on Mediterranean cold-water corals. Proceedings of the Royal Society of London, Series B, Biological 279: 1713-1723.

Maier, C., Schubert, A., Berzunza Sanchez, M.M., Weinbauer, M.G., Watremez, P. and Gattuso, J.-P. 2013. End of the century pCO2 levels do not impact calcification in Mediterranean cold-water corals. PLOS ONE 8: 10.1371/journal.pone.0062655.

Thresher, R.E., Tilbrook, B., Fallon, S., Wilson, N.C. and Adkins, J. 2011. Effects of chronic low carbonate saturation levels on the distribution, growth and skeletal chemistry of deep-sea corals and other seamount megabenthos. Marine Ecology Progress Series 442: 87-99.

Reviewed 4 December 2013