How does rising atmospheric CO2 affect marine organisms?

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Acclimation of a Cold-Water Coral to Ocean Acidification
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.

The authors write that "ocean acidification, often termed 'the evil twin of global warming,' is caused when the CO2 emitted by human activity dissolves into the oceans," while adding that a major gap in our understanding of the impacts of ocean acidification on life in the sea is our lack of information on "the potential of marine organisms to acclimate and adapt to increasing seawater acidity," noting further, in this regard, that our present understanding of the impacts of ocean acidification on marine life "relies heavily on results from short-term CO2 perturbation studies." Thus, they proceeded to conduct an experiment that they designed to help fill this important knowledge void.

What was done
Working with branches of Lophelia pertusa - which they collected from reefs off the coast of Norway, and which they describe as "the most common reef framework-forming and ecosystem engineering cold-water coral with a cosmopolitan distribution (Zibrowius, 1980; Cairns, 1994; Freiwald et al., 2004) - Form and Riebesell conducted a short-term (8-day) experiment and a long-term (178-day) experiment, wherein they employed different atmospheric CO2 treatments to create a range of water pH treatments that ranged from 8.029 to 7.768 in the 8-day study and from 7.944 to 7.755 in the 178-day study, and over which time intervals they measured the corals' growth rates.

What was learned
The two German researchers found that "short-term (1-week) high CO2 exposure resulted in a decline of calcification by 26-29% for a pH decrease of 0.1 unit and net dissolution of calcium carbonate." In contrast, however, they discovered that "L. pertusa was capable to acclimate to acidified conditions in long-term (6 months) incubations, leading to even slightly enhanced rates of calcification." And they add that in the long-term low-pH treatment, "net growth is sustained even in waters sub-saturated with respect to aragonite."

What it means
In light of the fact that the studied corals were able to acclimate to high-CO2 conditions over but half a year, think of what they could do in the way of evolving over the much longer period of time that would be required to boost earth's atmospheric CO2 concentration to an equivalent level. For some likely possibilities, consult the reviews of pertinent research papers that we have archived under the general heading of Evolution in our Subject Index.

Cairns, S.D. 1994. Scleractinia of the temperate north Pacific. Smithsonian Contributions to Zoology 557: 1-150.

Freiwald, A., Fossa, J.H., Grehan, A., Koslow, T. and Roberts, J.M. 2004. Cold-Water Coral Reefs. UNEP-WCMC, Cambridge, United Kingdom.

Zibrowius, H. 1980. Les Scleractiniaires de la Mediterranee et de l'Atlantique nord-oriental. Memoires de l'Institut Oceanographique. Monaco 11: 1-284.

Reviewed 5 September 2012