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Acropora Coral Fossils Show Evidence of Immunity to Predicted Future Levels of Ocean Acidification and Warming

Paper Reviewed
Stolarski, J., Bosellini, F.R., Wallace, C.C., Gothmann, A.M., Mazur, M., Domart-Coulon, I., Gutner-Hoch, E., Neuser, R.D., Levy, O., Shemesh, A. and Meibom, A. 2016. A unique coral biomineralization pattern has resisted 40 million years of major ocean chemistry change. Scientific Reports 6: 27579, DOI: 10.1038/srep27579.

For well over a decade, concerns about potential negative effects of so-called ocean acidification on marine life have loomed large, particularly for corals, where some scientists have gone so far as to predict their utter demise just a few short decades from now.

Long-time readers of CO2 Science, however, know better. They know that contrary to such forecasts, coral reefs remain far from the brink of extinction. For years we have highlighted countless peer-reviewed studies demonstrating that ocean acidification is largely a non-problem for corals and other marine life (see, for example, the many links found under the heading Ocean Acidification and Ocean Acidification and Warming found here). The latest such study to put yet another nail in the coffin of the ocean acidification scare story comes from Stolarski et al. (2016).

Publishing their work in the journal Scientific Reports, the team of eleven international researchers compared the skeletal structures of living Acropora corals with those of well-preserved fossil Acropora skeletons from the Eocene, Oligocene, and Miocene, noting that these latter organisms "have experienced major fluctuations in atmospheric CO2 levels (from greenhouse conditions of high pCO2 in the Eocene to low pCO2 ice-house conditions in the Oligocene-Miocene) and a dramatically changing ocean Mg/Ca ratio." By doing so, it could therefore be empirically determined whether or not higher levels of CO2 (i.e., ocean acidification) truly are a detriment to corals, interfering with the process of calcification and disrupting or weakening skeletal structure.

So is that what they found? Were these major reef building corals harmed by ocean acidification and temperature changes of conditions past?

In a word, no. In stark contrast, in fact, Stolarski et al. report that "the most diverse, widespread, and abundant reef-building coral genus Acropora (20 morphological groups and 150 living species) has not only survived these environmental changes, but has maintained its distinct skeletal biomineralization pattern for at least 40 My." Such "remarkable evolutionary stability," they continue, "exists despite major global geochemical fluctuations, from greenhouse (high pCO2) conditions and low seawater Mg/Ca (calcitic seas) in the Eocene to icehouse (low pCO2) conditions and rapidly increasing Mg/Ca (aragonite seas) during the Oligocene-Miocene."

The take home message of the Stolarski et al. paper is that the skeletal formation process of Acropora is, as they state, "strongly biologically controlled," uninhibited by changes in temperature or seawater chemistry, including seawater pH/ocean acidification conditions that are predicted to occur over the course of the next century and beyond.

Posted 6 January 2017