Coral Reef Laboratory, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, UK; Department of Biological Sciences, National University of Singapore, Singapore 117558, Singapore.
Coral Reef Laboratory, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, UK; Institute for Life Sciences (IFLS), University of Southampton, Highfield Campus, Southampton SO17 1BJ, UK.
Curr Biol. 2020 Jul 6;30(13):2433-2445.e3. doi: 10.1016/j.cub.2020.04.055. Epub 2020 May 21.
Coral bleaching, caused by the loss of brownish-colored dinoflagellate photosymbionts from the host tissue of reef-building corals, is a major threat to reef survival. Occasionally, bleached corals become exceptionally colorful rather than white. These colors derive from photoprotective green fluorescent protein (GFP)-like pigments produced by the coral host. There is currently no consensus regarding what causes colorful bleaching events and what the consequences for the corals are. Here, we document that colorful bleaching events are a recurring phenomenon in reef regions around the globe. Our analysis of temperature conditions associated with colorful bleaching events suggests that corals develop extreme coloration within 2 to 3 weeks after exposure to mild or temporary heat stress. We demonstrate that the increase of light fluxes in symbiont-depleted tissue promoted by reflection of the incident light from the coral skeleton induces strong expression of the photoprotective coral host pigments. We describe an optical feedback loop involving both partners of the association, discussing that the mitigation of light stress offered by host pigments could facilitate recolonization of bleached tissue by symbionts. Our data indicate that colorful bleaching has the potential to identify local environmental factors, such as nutrient stress, that can exacerbate the impact of elevated temperatures on corals, to indicate the severity of heat stress experienced by corals and to gauge their post-stress recovery potential. VIDEO ABSTRACT.
珊瑚白化是由于造礁珊瑚组织中棕色虫黄藻共生体的丧失而导致的，是珊瑚生存的主要威胁。偶尔，白化的珊瑚会变得异常多彩，而不是白色。这些颜色来自珊瑚宿主产生的光保护绿色荧光蛋白（GFP）样色素。目前对于导致多彩白化事件的原因以及对珊瑚的影响尚无共识。在这里，我们记录到，多彩白化事件是全球范围内珊瑚礁区域的一种反复出现的现象。我们对与多彩白化事件相关的温度条件的分析表明，珊瑚在暴露于温和或暂时的热应激后 2 至 3 周内会产生极端的颜色。我们证明，珊瑚骨骼对入射光的反射促进了共生体耗尽组织中光通量的增加，从而诱导了强烈的珊瑚宿主色素的光保护表达。我们描述了一个涉及共生体关联双方的光学反馈回路，讨论了宿主色素提供的光应激缓解可能有助于共生体对白化组织的再殖民化。我们的数据表明，多彩白化有可能识别局部环境因素，如营养压力，这些因素会加剧高温对珊瑚的影响，指示珊瑚经历的热应激的严重程度，并评估它们的应激后恢复潜力。视频摘要。
