How does rising atmospheric CO2 affect marine organisms?

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CO2 Effects on Hatch Size and Larval Growth of Walleye Pollock
Hurst, T.P., Fernandez, E.R. and Mathis, J.T. 2013. Effects of ocean acidification on hatch size and larval growth of walleye pollock (Theragra chalcogramma). ICES Journal of Marine Science 70: 812-822.

The authors write that "rising atmospheric concentrations of CO2 are predicted to decrease the pH of high-latitude oceans by 0.3 to 0.5 units by 2100," and they say that "because of their limited capacity for ion exchange, embryos and larvae of marine fishes are predicted to be more sensitive to elevated CO2 than juveniles and adults."

What was done
In a study designed to explore these particular predictions, Hurst et al. (2013) examined the direct effects of projected levels of ocean acidification on the eggs and larvae of walleye pollock in a series of laboratory experiments that focused on determining the effects of elevated CO2 levels on size-at-hatch and early larval growth rates, where treatments were selected to reflect ambient conditions and conditions predicted to occur in high latitude seas in the next century (a 400-600 ppm increase), as well as a significantly higher CO2 treatment (~1200 ppm).

What was learned
The three U.S. researchers found that "ocean acidification did not appear to negatively affect size or condition of early larval walleye pollock." In fact, they say there was "a trend toward larger body sizes among fish reared at elevated CO2 levels," while noting that this trend toward faster growth rates among larvae reared at elevated CO2 levels has also been observed in experiments with orange clownfish (Munday et al., 2009), as well as in the study of juvenile walleye pollock conducted by Hurst et al. (2012).

What it means
In the words of Hurst et al. (2013), their findings suggest that "the growth dynamics of early life stages of walleye pollock are resilient to projected levels of ocean acidification."

Hurst, T.P., Fernandez, E.R., Mathis, J.T., Miller, J.A., Stinson, C.S. and Ahgeak, E.F. 2012. Resiliency of juvenile walleye pollock to projected levels of ocean acidification. Aquatic Biology 17: 247-259.

Munday, P.L., Donelson, J.M., Dixson, D.L. and Endo, G.G.K. 2009. Effects of ocean acidification on the early life history of a tropical marine fish. Proceedings of the Royal Society of London, Series B, Biological Sciences 276: 3275-3283.

Reviewed 6 November 2013