How does rising atmospheric CO2 affect marine organisms?

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Effect of Elevated CO2 on Calcification by Oculina arbuscula Corals
Ries, J.B., Cohen, A.L. and McCorkle, D.C. 2010. A nonlinear calcification response to CO2-induced ocean acidification by the coral Oculina arbuscula. Coral Reefs 29: 661-674.

Climate alarmists contend that rising atmospheric CO2 concentrations will lead to a significant acidification of seawater that will in turn lead to significant -- and likely deadly -- reductions in coral calcification rates. Recent research, however, has called this claim into question; and the study reviewed here falls into this category.

What was done
The authors, as they describe it, "investigated the impact of CO2-induced ocean acidification on the temperate scleractinian coral Oculina arbuscula by rearing colonies for 60 days in experimental seawaters bubbled with air-CO2 gas mixtures of 409, 606, 903 and 2,856 ppm CO2, yielding average aragonite saturation statesA) of 2.6, 2.3, 1.6 and 0.8."

What was learned
First of all, Ries et al. observed that "following the initial acclimation phase, survivorship in each experimental treatment was 100%," while last of all, in regard to the corals' rates of calcification and linear extension, they say that "no significant difference was detected relative to the control treatment (ΩA = 2.6) for corals reared under ΩA of 2.3 and 1.6," which latter values correspond to pH reductions from current conditions of 0.08 and 0.26, respectively. And it is enlightening to note that the 0.26 pH reduction is approximately twice the maximum reduction derived from the analysis of Tans (2009) that would likely result from the burning of all fossil fuels in the crust of the earth.

What it means
The three researchers, in their words, "propose that the apparent insensitivity of calcification and linear extension within O. arbuscula to reductions in ΩA from 2.6 to 1.6 reflects the corals' ability to manipulate the carbonate chemistry at their site of calcification." And it would further appear that that ability should serve the corals well, no matter how much fossil fuel is burned before various non-CO2-producing forms of energy generation become sufficiently developed to supply the bulk of the world's energy needs.

Tans, P. 2009. An accounting of the observed increase in oceanic and atmospheric CO2 and an outlook for the future. Oceanography 22: 26-35.

Reviewed 24 November 2010