How does rising atmospheric CO2 affect marine organisms?

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Organismal Response to Ocean Acidification: The Role of Evolution
Sunday, J.M., Crim, R.N., Harley, C.D.G. and Hart, M.W. 2011. Quantifying rates of evolutionary adaptation in response to ocean acidification. PLoS ONE 6: e22881.

The authors write that the presumed acidification of earth's oceans is predicted to impact marine biodiversity via "physiological effects impacting growth, survival, reproduction and immunology, leading to changes in species abundances and global distributions." However, they note that "the degree to which these changes will play out critically depends on the evolutionary rate at which populations will respond to natural selection imposed by ocean acidification," and they say that this phenomenon "remains largely unquantified," citing the work of Stockwell et al. (2003) and Gienapp et al. (2008).

What was done
Working with a sea urchin species (Strongylocentrotus franciscanus) and a mussel species (Mytilus trossulus) in a full-factorial breeding study, Sunday et al. measured the potential for an evolutionary response to ocean acidification in the larval development rate of the two coastal invertebrates.

What was learned
The four researchers report that "the sea urchin species Stronglyocentrotus franciscanus has vastly greater levels of phenotypic and genetic variation for larval size in future CO2 conditions compared to the mussel species Mytilus trossulus," and using these findings, they go on to demonstrate that "S. franciscanus may have faster evolutionary responses within 50 years of the onset of predicted year-2100 CO2 conditions despite having lower population turnover rates."

What it means
Sunday et al. conclude their study by saying their comparisons suggest that "information on genetic variation, phenotypic variation, and key demographic parameters, may lend valuable insight into relative evolutionary potentials across a large number of species," thereby also indicating that simplistic climate envelope models of species redistributions in a future CO2-enriched and possibly warmer world are just not up to the task of providing a picture of future biological reality. And they solidify this view by noting that "a genetic basis for variation in CO2 responses has been found in the three previous studies in which it has been sought (Langer et al., 2009; Parker et al., 2011; Pistevos et al., 2011), supporting the notion that genetic variation exists at some level for almost all quantitative characters (Roff, 1997)."

Gienapp, P., Teplitsky, C., Alho, J.S., Mills, J.A. and Merila, J. 2008. Climate change and evolution: disentangling environmental and genetic responses. Molecular Ecology 17: 167-178.

Langer, G., Nehrke, G., Probert, I., Ly, J. and Ziveri, P. 2009. Strain-specific responses of Emiliania huxleyi to changing seawater carbonate chemistry. Biogeosciences 6: 2637-2646.

Parker, L.M., Ross, P.M. and O'Connor, W.A. 2011. Populations of the Sydney rock oyster, Saccostrea glomerata, vary in response to ocean acidification. Marine Biology 158: 689-697.

Pistevos, J.C.A., Calosi, P., Widdicombe, S. and Bishop, J.D.D. 2011. Will variation among genetic individuals influence species responses to global climate change? Oikos 120: 675-689.

Roff, D.A. 1997. Evolutionary Quantitative Genetics. Chapman and Hall, New York, New York, USA.

Stockwell, C.A., Hendry, A.P. and Kinnison, M.T. 2003. Contemporary evolution meets conservation biology. Trends in Ecology and Evolution 18: 94-101.

Reviewed 16 November 2011