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Resistance to ocean acidification in coral reef taxa is not gained by acclimatization


Ocean acidification (OA) is a major threat to coral reefs, which are built by calcareous species. However, long-term assessments of the impacts of OA are scarce, limiting the understanding of the capacity of corals and coralline algae to acclimatize to high partial pressure of carbon dioxide (\({p}_{\mathrm{CO}_{2}}\)) levels. Species-specific sensitivities to OA are influenced by its impacts on chemistry within the calcifying fluid (CF). Here, we investigate the capacity of multiple coral and calcifying macroalgal species to acclimatize to elevated \({p}_{\mathrm{CO}_{2}}\) by determining their chemistry in the CF during a year-long experiment. We found no evidence of acclimatization to elevated \({p}_{\mathrm{CO}_{2}}\) across any of the tested taxa. The effects of increasing seawater \({p}_{\mathrm{CO}_{2}}\) on the CF chemistry were rapid and persisted until the end of the experiment. Our results show that acclimatization of the CF chemistry does not occur within one year, which confirms the threat of OA for future reef accretion and ecological function.

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All data are available on the public data repository BCO-DMO (

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Peer review information: Nature Climate Change thanks Catherine Cole and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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We thank A.-M. Comeau-Nisumaa, J. D’Olivo and P. Edmunds for support for this study. Funding support was as follows: M.T.M. by an ARC Laureate Fellowship (LF120100049) and ARC Centre of Excellence for Coral Reef Studies (CE140100020); S.C. by an ARC DECRA (DE160100668); C.E.C. by ARC Centre of Excellence for Coral Reef Studies (CE140100020) and a Rutherford Discovery Fellowship (Royal Society of New Zealand; RDF-VUW1701); R.C.C. by a National Science Foundation grant OCE 14-15268, the Moorea Coral Reef LTER programme (NSF OCE 12-36905) and from the Gordon and Betty Moore Foundation. The authors also acknowledge the facilities, and scientific and technical assistance, of the University of Western Australia’s Centre for Microscopy, Characterisation and Analysis (CMCA). Research was completed under permits issued by the Haut-commissariat de la République en Polynésie Francaise (DRRT) (Protocole d’Accueil 2015–2016). This is contribution number 286 of the CSUN Marine Biology Program.

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S.C. wrote the paper, prepared the experiment, ran the geochemical analyses and analysed the data. C.E.C. wrote the paper and conducted geochemical analyses. T.M.D. performed geochemical analyses. S.S.D. performed the flume experiment. R.C.C and M.T.M. provided vital laboratory facilities. All authors edited the manuscript, contributed intellectual expertise and approved of its submission.

Correspondence to S. Comeau.

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Fig. 1: Effects of four \({p}_{\mathrm{CO}_{2}}\) treatments (~360, 550, 700 and 1,050 μatm) on the surface area-normalized net calcification rates.
Fig. 2: Estimates of pHcf at the end of the one-year experiment.
Fig. 3: Estimates of DICcf at the end of the one-year incubation period.
Fig. 4: Ratio between Ca2+cf and Ca2+SW in the four studied corals.
Fig. 5: Temporal variations of Acropora and Porites pHcf and DICcf.
Fig. 6: Schematic summary of the responses to OA measured in the corals Acropora, Psammocora, Porites and Pocillopora.