How does rising atmospheric CO2 affect marine organisms?

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Growth, Calcification and Mortality of Juvenile Mussels Exposed to Ocean Acidification
Range, P., Pilo, D., Ben-Hamadou, R., Chicharo,M.A., Matias, D., Joaquim, S., Oliveira, A.P. and Chicharo, L. 2012. Seawater acidification by CO2 in a coastal lagoon environment: Effects on life history traits of juvenile mussels Mytilus galloprovincialis. Journal of Experimental Marine Biology and Ecology 424-425: 89-98.

Ocean acidification is considered by climate alarmists to be detrimental to nearly all sea creatures; and the early life-stages of these organisms are generally thought to be the most sensitive stages to this environmental change.

What was done
In a study designed to explore these assumptions, the authors tested the effects of seawater acidification by CO2 addition, leading to reductions of 0.3 and 0.6 pH units, on six-month-old juvenile mussels (Mytilus galloprovincialis), which they obtained from a mussel raft on the Ria de Ares-Betanzos of Northwest Spain, focusing their attention on growth, calcification and mortality.

What was learned
The eight researchers, all from Portugal, report that the growth of the mussels, measured as relative increases in shell size and body weight during the 84 days of the experiment, "did not differ among treatments." In fact, they say that a tendency for faster shell growth under elevated CO2 was apparent, "at least during the first 60 days of exposure." In the case of calcification, however, they indicate that this process was reduced, but by only up to 9%. Yet even here they state that "given that growth was unaffected, the mussels clearly maintained the ability to lay down CaCO3, which suggests post-deposition dissolution as the main cause for the observed loss of shell mass." Last of all, with respect to mortality, Range et al. write that "mortality of the juvenile mussels during the 84 days was small (less than 10%) and was unaffected by the experimental treatments."

What it means
In summing up the implications of their findings, the Portuguese scientists say that they further support the fact that "there is no evidence of CO2-related mortalities of juvenile or adult bivalves in natural habitats, even under conditions that far exceed the worst-case scenarios for future ocean acidification (Tunnicliffe et al., 2009)."

Tunnicliffe, V., Davies, K.T.A., Butterfield, D.A., Embley, R.W., Rose, J.M., and Chadwick Jr., W.W. 2009. Survival of mussels in extremely acidic waters on a submarine volcano. Nature Geoscience 2: 344-348.

Reviewed 23 January 2013