title: Future reef decalcification under a business-as-usual CO2 emission scenario.
abstract: Increasing atmospheric partial pressure of CO2 (pCO2) is a major threat to coral reefs, but some argue that the threat is mitigated by factors such as the variability in the response of coral calcification to acidification, differences in bleaching susceptibility, and the potential for rapid adaptation to anthropogenic warming. However the evidence for these mitigating factors tends to involve experimental studies on corals, as opposed to coral reefs, and rarely includes the influence of multiple variables (e.g., temperature and acidification) within regimes that include diurnal and seasonal variability. Here, we demonstrate that the inclusion of all these factors results in the decalcification of patch-reefs under business-as-usual scenarios and reduced, although positive, calcification under reduced-emission scenarios. Primary productivity was found to remain constant across all scenarios, despite significant bleaching and coral mortality under both future scenarios. Daylight calcification decreased and nocturnal decalcification increased sharply from the preindustrial and control conditions to the future scenarios of low (reduced emissions) and high (business-as-usual) increases in pCO2. These changes coincided with deeply negative carbonate budgets, a shift toward smaller carbonate sediments, and an increase in the abundance of sediment microbes under the business-as-usual emission scenario. Experimental coral reefs demonstrated highest net calcification rates and lowest rates of coral mortality under preindustrial conditions, suggesting that reef processes may not have been able to keep pace with the relatively minor environmental changes that have occurred during the last century. Taken together, our results have serious implications for the future of coral reefs under business-as-usual environmental changes projected for the coming decades and century.
authors.affiliation: Global Change Institute, School of Biological Sciences, Australian Research Council Centre for Excellence in Coral Reef Studies, Australian Centre for Ecogenomics, and Advanced Water Management Centre, University of Queensland, St. Lucia, QLD 4072, Australia.
authors.forename: Sophie G
authors.initials: SG
authors.lastname: Dove
authors.forename: David I
authors.initials: DI
authors.lastname: Kline
authors.forename: Olga
authors.initials: O
authors.lastname: Pantos
authors.forename: Florent E
authors.initials: FE
authors.lastname: Angly
authors.forename: Gene W
authors.initials: GW
authors.lastname: Tyson
authors.forename: Ove
authors.initials: O
authors.lastname: Hoegh-Guldberg
mesh_terms: D000397:Air Pollution / Q000009:adverse effects*; D000704:Analysis of Variance; D000818:Animals; D037421:Anthozoa / Q000254:growth & development* / Q000378:metabolism; D002113:Calcification, Physiologic / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002245:Carbon Dioxide / Q000032:analysis*; D003247:Conservation of Natural Resources; D057894:Coral Reefs; D017931:DNA Primers / Q000235:genetics; D019015:Geologic Sediments / Q000382:microbiology; D054892:Metagenome / Q000235:genetics; D010140:Pacific Ocean; D016133:Polymerase Chain Reaction; D011793:Queensland; D012621:Seasons; D012623:Seawater / Q000737:chemistry*; D013696:Temperature
chemical_list: D017931:DNA Primers; D002245:Carbon Dioxide; D002118:Calcium
keywords: carbonate balance; climate change; metabolism