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Elevated Temperature Mitigates the Negative Impacts of Ocean Acidification on Porites Calcification

Paper Reviewed
Cole, C., Finch, A.A., Hintz, C., Hintz, K. and Allison, N. 2018. Effects of seawater pCO2 and temperature on calcification and productivity in the coral genus Porites spp.: and exploration of potential interaction mechanisms. Coral Reefs 37: 471-481.

Writing as background for their work, Cole et al. (2018) say that "understanding how rising seawater pCO2 and temperatures impact coral aragonite accretion is essential for predicting the future of reef ecosystems." Consequently, it was their objective to investigate the relationship between seawater temperature and pCO2 (i.e., ocean acidification) on the calcification rates of massive Porites corals.

To accomplish this effort, the researchers conducted two separate experiments where they cultured seven Porites genotypes at temperatures of 25 or 28°C and pCO2 concentrations of 180, 260 or 750 µatm, corresponding to pCO2 concentrations of the last glacial maximum, present day and that predicted for the end of this century, respectively.

Results of the two experiments revealed, in the words of the authors, that "increasing seawater temperature enhanced calcification in almost all corals, and the magnitude of this effect was seawater pCO2 dependent," such that "the 3°C temperature increase enhanced calcification on average by 3% at 180 µatm, by 35% at 260 µatm and by > 300% at 750 µatm." Accordingly, they add that "at high seawater pCO2, this increase substantially mitigated the effects of ocean acidification on calcification: at 25°C the mean Porites spp. calcification rate at seawater pCO2 750 µatm is ~40% of the rate observed at 180 µatm. In contrast, at 28°C this figure is ~100%."

Not surprisingly, Cole et al. conclude that their study results indicate that "increasing seawater temperature can offset the suppression of calcification by ocean acidification in this coral species." And that is great news for those concerned about the future status of this massive coral.

Posted 6 August 2018