pH variability at volcanic CO2 seeps regulates coral calcifying fluid chemistry

Steeve Comeau*, Christopher E. Cornwall, Tom Shlesinger, Mia Hoogenboom, Ralph Mana, Malcolm T. McCulloch, Riccardo Rodolfo-Metalpa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Coral reefs are iconic ecosystems with immense ecological, economic and cultural value, but globally their carbonate-based skeletal construction is threatened by ocean acidification (OA). Identifying coral species that have specialised mechanisms to maintain high rates of calcification in the face of declining seawater pH is of paramount importance in predicting future species composition, and growth of coral reefs. Here, we studied multiple coral species from two distinct volcanic CO2 seeps in Papua New Guinea to assess their capacity to control their calcifying fluid (CF) chemistry. Several coral species living under conditions of low mean seawater pH, but with either low or high variability in seawater pH, were examined and compared with those living in ‘normal’ (non-seep) ambient seawater pH. We show that when mean seawater pH is low but highly variable, corals have a greater ability to maintain constant pHcf in their CF, but this characteristic was not linked with changes in abundance. Within less variable low pH seawater, corals with limited reductions in pHcf at the seep sites compared with controls tended to be more abundant at the seep site than at the control site. However, this finding was strongly influenced by a single species (Montipora foliosa), which was able to maintain complete pHcf homeostasis. Overall, although our findings indicate that there might be an association between ecological success and greater pHcf homeostasis, further research with additional species and at more sites with differing seawater pH regimes is required to solidify inferences regarding coral ecological success under future OA.

Original languageEnglish
Pages (from-to)2751-2763
Number of pages13
JournalGlobal Change Biology
Issue number8
StatePublished - Apr 2022
Externally publishedYes


FundersFunder number
French grant scheme Fonds Pacifique1598
Milne Bay Provincial Research Committee
New Ireland Provincial Administration
Association pour la Recherche sur le CancerLF120100049, VUW‐1701
Centre of Excellence for Coral Reef Studies, Australian Research CouncilCE140100020
Australian Research CouncilDE160100668
Agence Nationale de la RechercheANR15CE02‐0006‐01
National Drug Research Institute


    • Papua New Guinea
    • abundance
    • calcification
    • calcifying fluid
    • coral
    • coral reefs
    • dissolved inorganic carbon
    • ocean acidification


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