Courtial L. auteur aut IRD Ferrier-Pages C. auteur aut IRD Jacquet S. auteur aut IRD Rodolfo-Metalpa Riccardo auteur aut IRD Reynaud S. auteur aut IRD Rottier C. auteur aut IRD Houlbrèque Fanny auteur aut IRD text journalArticle eng text/pdf reformatted digital access Coral bleaching events are predicted to occur more frequently in the coming decades with global warming. The susceptibility of corals to bleaching during thermal stress episodes depends on many factors, including the magnitude of thermal stress and irradiance. The interactions among these two factors, and in particular with ultraviolet radiation (UVR), the most harmful component of light, are more complex than assumed, and are not yet well understood. This paper explores the individual and combined effects of temperature and UVR on the metabolism of Acropora muricata, one of the most abundant coral species worldwide. Particulate and dissolved organic matter (POM/DOM) fluxes and organic matter (OM) degradation by the mucus-associated bacteria were also monitored in all conditions. The results show that UVR exposure exacerbated the temperature-induced bleaching, but did not affect OM fluxes, which were only altered by seawater warming. Temperature increase induced a shift from POM release and DOM uptake in healthy corals to POM uptake and DOM release in stressed ones. POM uptake was linked to a significant grazing of pico- and nanoplankton particles during the incubation, to fulfil the energetic requirements of A. muricata in the absence of autotrophy. Finally, OM degradation by mucus-associated bacterial activity was unaffected by UVR exposure, but significantly increased under high temperature. Altogether, our results demonstrate that seawater warming and UVR not only affect coral physiology, but also the way corals interact with the surrounding seawater, with potential consequences for coral reef biogeochemical cycles and food webs. specialized Acropora muricata Thermal stress UV radiation Climate change Organic matter fluxes Microbial loop 036 021 6 8 1190-1199 2017 2046-6390 https://www.documentation.ird.fr/hor/fdi:010070919 10.1242/bio.026757 2046-6390 [F B010070919] https://www.documentation.ird.fr/hor/fdi:010070919 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers17-09/010070919.pdf IRD - Base Horizon / Pleins textes 2017-10-03 2023-07-11 fdi:010070919 fre