How does rising atmospheric CO2 affect marine organisms?

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Can Migrating Corals Outpace Ocean Warming and Acidification?
Couce, E., Ridgwell, A. and Hendy, E.J. 2013. Future habitat suitability for coral reef ecosystems under global warming and ocean acidification. Global Change Biology 19: 3592-3606.

The authors say "there is concern that the growing frequency and severity of mass bleaching episodes may lead to species composition shifts and functional collapse in coral reefs in the near future." On the other hand, they also note that global warming "has the potential to improve currently marginal environmental conditions and extend the range of tropical coral reefs into higher latitudes," as is "demonstrated in the fossil record in response to warmer geological periods (e.g., Lighty et al., 1978; Veron, 1992; Precht and Aronson, 2004; Greenstein and Pandolfi, 2008; Woodroffe et al., 2010; Kiessling et al., 2012)." But what if ocean acidification occurs concurrently?

What was done
To investigate this potential situation, Couce et al. employed "a suite of statistical models based on the environmental factors thought to be limiting to the present equilibrium distribution of shallow-water coral reefs, perturbing them with Earth System Model projected future sea surface temperatures and aragonite saturation changes (the simulations used in Turley et al., 2010)," while considering "a range of potential future CO2 emissions scenarios," but focusing on "the consequences of the 'A2' scenario (characterized by regionally oriented economic development and high population growth, expecting ca. 850 ppm CO2 by 2100)."

What was learned
After all was said and done, the three UK researchers found that "contrary to expectations, the combined impact of ocean surface temperature rise and acidification leads to little, if any, degradation in future habitat suitability across much of the Atlantic and areas currently considered 'marginal' for tropical corals, such as the eastern Equatorial Pacific." And they note, in this regard, that "these results are consistent with fossil evidence of range expansions during past warm periods."

What it means
In terms of the nitty-gritty here-and-now, Couce et al. conclude by stating that their results "present important implications for future coral reef management, as they suggest that more emphasis should be placed on conservation efforts on marginal reefs as they are not necessarily a 'lost cause'."

Greenstein, B.J. and Pandolfi, J.M. 2008. Escaping the heat: range shifts of reef coral taxa in costal Western Australia. Global Change Biology 14: 513-528.

Kiessling, W., Simpson, C., Beck, B., Mewis, H. and Pandolfi, J.M. 2012. Equatorial decline of reef corals during the last Pleistocene interglacial. Proceedings of the National Academy of Sciences USA 109: 21,378-21,383.

Lighty, R.G., Macintyre, I.G. and Stuckenrath, R. 1978. Submerged early Holocene barrier reef south-east Florida shelf. Nature 276: 59-60.

Precht, W.F. and Aronson, R.B. 2004. Climate flickers and range shifts of reef corals. Frontiers in Ecology and the Environment 2: 307-314.

Turley, C., Eby, M., Ridgwell, A.J., Schmidt, D.N., Findlay, H.S., Brownlee, C., Riebesel, U., Gattuso, J.-P., Fabry, V.J. and Feely, R.A. 2010. The societal challenge of ocean acidification. Marine Pollution Bulletin 60: 787-792.

Veron, J. 1992. Environmental control of Holocene changes to the world's most northern hermatypic coral outcrop. Pacific Science 46: 402-425.

Woodroffe, C.D., Brooke, B.P., Linklater, M., Kennedy, D.M., Jones, B.G., Buchanan, C., Mleczko, R., Hua, Q. and Zhao, J. 2010. Response of coral reefs to climate change: expansion and demise of the southernmost pacific coral reef. Geophysical Research Letters 37: 10.1029/2010GL044067.

Reviewed 29 January 2014