Coral calcification in a changing World and the interactive dynamics of pH and DIC upregulation

Malcolm T. McCulloch, Juan Pablo D'Olivo, James Falter, Michael Holcomb, Julie A. Trotter

Research output: Contribution to journalArticlepeer-review

93 Citations (Scopus)

Abstract

Coral calcification is dependent on the mutualistic partnership between endosymbiotic zooxanthellae and the coral host. Here, using newly developed geochemical proxies (λ11B and B/Ca), we show that Porites corals from natural reef environments exhibit a close (r2 ~0.9) antithetic relationship between dissolved inorganic carbon (DIC) and pH of the corals' calcifying fluid (cf). The highest DICcf (~ × 3.2 seawater) is found during summer, consistent with thermal/light enhancement of metabolically (zooxanthellae) derived carbon, while the highest pH cf (~8.5) occurs in winter during periods of low DICcf (~ × 2 seawater). These opposing changes in DIC cf and pH cf are shown to maintain oversaturated but stable levels of carbonate saturation (Ωcf ~ × 5 seawater), the key parameter controlling coral calcification. These findings are in marked contrast to artificial experiments and show that pH cf upregulation occurs largely independent of changes in seawater carbonate chemistry, and hence ocean acidification, but is highly vulnerable to thermally induced stress from global warming.

Original languageEnglish
Article number15686
JournalNature Communications
Volume8
DOIs
Publication statusPublished - 30 May 2017

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