High Coral Recruitment Despite Coralline Algal Loss Under Extreme Environmental Conditions

Clément Tanvet, Francesca Benzoni, Christophe Peignon, Gérard Thouzeau, Riccardo Rodolfo-Metalpa

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


The crucial role of crustose coralline algae (CCA) in inducing hard coral larval settlement and ensuring the replenishment of coral reefs is widely accepted, and so are the negative effects of anthropogenic CO2 emissions on both CCA abundance and coral development. However, diversified and well-developed coral reef communities have been recently discovered in natural conditions where CCA and corals would not be expected to thrive. Back-reef pools, volcanic CO2 vents, mangrove estuaries, and semi-enclosed lagoons systems can present seawater pH, temperature, and dissolved oxygen values reaching or even exceeding the conditions currently predicted by the Inter Panel on Climate Change (IPCC) for 2100. In the semi-enclosed lagoon of Bouraké (New Caledonia, southwest Pacific Ocean), seawater pHT, dissolved oxygen, and temperatures regularly fluctuate with the tide reaching respectively minimum values of 7.23 pHT units, 2.28 mg O2 L-1, and maximum of 33.85°C. This study reports the effect of such extreme environmental conditions on hard coral recruitment and CCA originally settled at a forereef on artificial substrates that were transplanted over two years in two fringing reef and at the Bouraké lagoon. Our data emphasize the negative effects of the extreme conditions in our study sites on the CCA, which decreased in cover by ca. 80% and lost in the competition with turf algae, which, in turn, increased up to 162% at the end of the two years. Conversely, hard coral recruitment remained high at Bouraké throughout the study, three-fold higher than at two sites located outside Bouraké where environmental conditions were typical for coastal fringing reefs. Our findings show that while such extreme, climate change like-conditions have a direct and adverse effect on CCA abundance, and despite a certain persistence, coral larvae settlement was not affected. Based on previous findings from Bouraké, and the present observations, both coral recruits and adults seem to be unaffected despite the extreme environmental conditions. This study supports previous research illustrating how extreme natural and variable environments may reveal unexpected and positive insights on the processes underlying coral acclimatization and adaptation to global change.
Original languageEnglish (US)
JournalFrontiers in Marine Science
StatePublished - Jun 16 2022

Bibliographical note

KAUST Repository Item: Exported on 2022-09-14
Acknowledged KAUST grant number(s): FCC/1/1973-49-01
Acknowledgements: We wish to express our thanks to the captains of the IRD vessels and the diving technical staff for their fieldwork assistance. We thank Dr. Mehdi Adjeroud for providing us with the tiles used and for scientific advice on coral recruitment. We thank Dr. Claude Payri and Dr. Christopher Cornwall for their help and expertise regarding the assessment of organisms percentage cover and for CCA taxonomy and health review. We also thank the Province Sud of New-Caledonia for sample collection permits (no. 3413-2019). We are indebted to Federica Maggioni for environmental data sharing. We thank Yuri Artioli for his help throughout the reviewing and editing process of this article. This study was supported by the French grant scheme Fonds Pacifique (no. 1976; project SuperCoraux). CT received a PhD fellowship from the University of Western Brittany (UBO) and the Brittany region (France). This study has also received financial support from the CNRS through the MITI interdisciplinary programs and was supported by ISblue project, Interdisciplinary graduate school for the blue planet (ANR-17-EURE-0015) and co-funded by a grant from the French government under the program “Investissements d’Avenir”. Funding for FB was provided by KAUST baseline research funding and award FCC/1/1973-49-01.


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