Van Wynsberge S., Ladet E., Chevillard C., Le Gendre R., Maamaatuaiahutapu M., Moeroa M., Remoissenet G., Richmond T., Poltavtseef L., Tepapatahi T., Teaka R., Teara M., Tefau A., Petton S., Jullien S., Lafille M. A., Andréfouët Serge. (2026). Optimised thermal-stress indices explain giant clam bleaching observations in a semi-closed atoll lagoon. Coral Reefs, [Early access], p. [17 p.]. ISSN 0722-4028.
Titre du document
Optimised thermal-stress indices explain giant clam bleaching observations in a semi-closed atoll lagoon
Année de publication
2026
Auteurs
Van Wynsberge S., Ladet E., Chevillard C., Le Gendre R., Maamaatuaiahutapu M., Moeroa M., Remoissenet G., Richmond T., Poltavtseef L., Tepapatahi T., Teaka R., Teara M., Tefau A., Petton S., Jullien S., Lafille M. A., Andréfouët Serge
Source
Coral Reefs, 2026,
[Early access], p. [17 p.] ISSN 0722-4028
Giant clams (Tridacna maxima) are abundant in French Polynesia semi-closed atolls, but the sustainability of the ecosystem services they provide has been challenged by recent mass bleaching events. Being able to accurately anticipate the risks of bleaching is needed to implement timely and effective mitigation strategies, but no method currently exists to assess bleaching risk from environmental data in these lagoons. To fill this gap, we used a hindcast approach to simulate the lagoon temperature experienced by giant clams at Reao Atoll (Tuamotu Archipelago) from 1993 to 2024. We then compared the reconstructed temperature time series with T. maxima bleaching states and size structures and densities during three El Ni & ntilde;o-induced heatwaves between 2016 and 2024. The 2016 event was the most stressful for giant clams, with 79.9% of individuals totally bleached. The 2017 and 2024 heatwaves induced lower bleaching than in 2016 despite an exposure to higher accumulated temperature stress levels, suggesting that giant clams' bleaching thermal threshold had increased after 2016. These observations were used to validate a new bleaching risk index (DHWT.maxima), inspired by NOAA's Coral Reef Watch coral bleaching indices, but optimised to account for the history of giant clam bleaching levels after several exposures to thermal stress. The newly designed index can be used to trigger local initiatives to mitigate the effect of bleaching on giant clam farming at Reao, and the method used in this study provides a framework to revisit the amount of thermal stress endured by symbiotic species in enclosed lagoon water bodies.
Plan de classement
Limnologie biologique / Océanographie biologique [034]
;
Ecologie, systèmes aquatiques [036]
;
Ressources halieutiques [040]
;
Etudes, transformation, conservation du milieu naturel [082]
Description Géographique
POLYNESIE FRANCAISE ; TUAMOTU
Localisation
Fonds IRD [F B010096936]
Identifiant IRD
fdi:010096936
