Courtial Lucile, Ferrier-Pagès Christine, Jacquet Stéphan, Rodolfo-Metalpa Riccardo, Reynaud Stéphanie, Rottier Cécile, Houlbrèque Fanny
Sorbone Universités, UPMC, 4 Place Jussieu, 75252 Paris Cedex 05, France
Centre Scientifique de Monaco, Equipe Ecophysiologie, 8 Quai Antoine 1er, 98000, Monaco (Principality).
Biol Open. 2017 Aug 15;6(8):1190-1199. doi: 10.1242/bio.026757.
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 , 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 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.
随着全球变暖，预计未来几十年珊瑚白化事件将更频繁地发生。在热应激事件期间，珊瑚对白化的易感性取决于许多因素，包括热应激的强度和辐照度。这两个因素之间的相互作用，特别是与光中最有害的成分紫外线辐射（UVR）之间的相互作用，比设想的更为复杂，目前尚未得到充分理解。本文探讨了温度和UVR对全球最丰富的珊瑚物种之一的新陈代谢的单独和综合影响。在所有条件下，还监测了颗粒和溶解有机物（POM/DOM）通量以及黏液相关细菌对有机物（OM）的降解情况。结果表明，紫外线辐射暴露加剧了温度诱导的白化现象，但不影响有机物通量，有机物通量仅因海水变暖而改变。温度升高导致健康珊瑚从释放POM和吸收DOM转变为应激珊瑚吸收POM和释放DOM。在培养过程中，POM的吸收与对微微型和微型浮游生物颗粒的大量摄食有关，以满足在缺乏自养情况下的能量需求。最后，黏液相关细菌活动对有机物的降解不受紫外线辐射暴露的影响，但在高温下显著增加。总之，我们的结果表明，海水变暖和紫外线辐射不仅影响珊瑚生理，还影响珊瑚与周围海水相互作用的方式，这可能对珊瑚礁生物地球化学循环和食物网产生潜在影响。
