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Cold-Water Corals in an Acidifying Ocean: How Might They Fare?

Paper Reviewed
Rodolfo-Metalpa, R., Montagna, P., Aliani, S., Borghini, M., Canese, S., Hall-Spencer, J.M., Foggo, A., Milazzo, M., Taviani, M and Houlbreque, F. 2015. Calcification is not the Achilles' heel of cold-water corals in an acidifying ocean. Global Change Biology 21: 2238-2248.

Introducing their recent publication in Global Change Biology, Rodolfo-Metalpa et al. (2015) say there are concerns that cold-water corals are even more vulnerable than their warm-water counterparts to rising atmospheric CO2 concentrations, since "they live in areas where aragonite saturation is lower than in the tropics and is falling rapidly due to CO2 emissions." And, hence, they set about to see if such was really the case.

This they did by first providing laboratory evidence, as shown in the figure below, that both net and gross calcification rates of three cold-water corals -- Caryophyllia smithii, Dendrophyllia cornigera and Desmophyllum dianthus -- are not affected by the pCO2 levels that many expect to prevail by the end of the current century (1058 µatm). Second on their to-do list, the ten researchers transplanted several D. dianthus specimens to a depth of 350 meters, where the pCO2 was 448 µatm, and to a 3-meter depth near a CO2 seep in oligotrophic waters where the pCO2 was 2879 µatm, finding that "the transplants calcified at the same rates regardless of the pCO2, confirming their resilience to acidification."

Net and gross calcification rates of the three Mediterranean cold-water corals held in aquaria during a one-month acclimation period at normal pCO2 levels followed by three months at normal and increased pCO2 levels. Adapted from Rodolfo-Metalpa et al. (2015).

As a result of these findings, Rodolfo-Metalpa et al. conclude their report with the almost exact same words as those comprising the title of their paper: "our observations in aquaria and in field transplants reveal that calcification is not the Achilles' heel of cold-water corals facing ocean acidification."

Posted 24 August 2015