RT Journal Article SR Electronic T1 Effects of temperature and UVR on organic matter fluxes and the metabolic activity of Acropora muricata JF Biology Open JO Biology Open FD Company of Biologists SP 1190 OP 1199 DO 10.1242/bio.026757 VO 6 IS 8 A1 Courtial, Lucile A1 Ferrier-Pagès, Christine A1 Jacquet, Stéphan A1 Rodolfo-Metalpa, Riccardo A1 Reynaud, Stéphanie A1 Rottier, Cécile A1 Houlbrèque, Fanny YR 2017 UL http://bio.biologists.org/content/6/8/1190.abstract AB 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 ultra-violet 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.