全球海洋热浪频率和强度的增加导致了浅水中底栖生物的大规模死亡和生物多样性的丧失。地中海也不例外，栖息地形成八放珊瑚的浅水种群面临局部灭绝的威胁。受海洋热浪影响较小的中光带可能在这些物种的保护策略中具有生态重要性。然而，我们对中光带八放珊瑚全生物体对海水温度变化的响应的理解仍然有限。为了解决这一知识差距，我们对地中海标志性八放珊瑚红珊瑚 Corallium rubrum 进行了研究，样本采集自 60 米深处，温度为 15 度。我们将珊瑚暴露在它们偶尔经历的温度（18 度）和如果全球变暖继续，可能在本世纪末出现的温度（21 度）下。我们还测试了珊瑚对极冷和极热温度（12 度和24 度）的反应。我们的结果显示，C. rubrum 对持续两个月的温度暴露（12-21 度）具有较高的耐受性，没有珊瑚骨架出现组织丢失、进食能力降低、应激诱导的基因表达或寄主-细菌共生的破坏迹象。然而，在 24 度时，我们观察到 Spirochaetaceae 相对丰度的急剧减少，而这些细菌在健康条件下是主要的细菌共生体，同时 Vibrionaceae 的相对丰度增加。在暴露两周后，我们还观察到组织丢失和肿瘤坏死因子受体 1 基因的过度表达。鉴于全球变暖的持续进行，我们的研究有助于预测海底中光带珊瑚礁以及依赖它们的生物多样性在海洋热浪中可能面临的后果。© 2023. BioMed Central Ltd., part of Springer Nature.

Marine heat waves (MHWs) have increased in frequency and intensity worldwide, causing mass mortality of benthic organisms and loss of biodiversity in shallow waters. The Mediterranean Sea is no exception, with shallow populations of habitat-forming octocorals facing the threat of local extinction. The mesophotic zone, which is less affected by MHWs, may be of ecological importance in conservation strategies for these species. However, our understanding of the response of mesophotic octocoral holobionts to changes in seawater temperature remains limited. To address this knowledge gap, we conducted a study on an iconic Mediterranean octocoral, the red coral Corallium rubrum sampled at 60 m depth and 15 °C. We exposed the colonies to temperatures they occasionally experience (18 °C) and temperatures that could occur at the end of the century if global warming continues (21 °C). We also tested their response to extremely cold and warm temperatures (12 °C and 24 °C). Our results show a high tolerance of C. rubrum to a two-month long exposure to temperatures ranging from 12 to 21 °C as no colony showed signs of tissue loss, reduced feeding ability, stress-induced gene expression, or disruption of host-bacterial symbioses. At 24 °C, however, we measured a sharp decrease in the relative abundance of Spirochaetaceae, which are the predominant bacterial symbionts under healthy conditions, along with a relative increase in Vibrionaceae. Tissue loss and overexpression of the tumor necrosis factor receptor 1 gene were also observed after two weeks of exposure. In light of ongoing global warming, our study helps predict the consequences of MHWs on mesophotic coralligenous reefs and the biodiversity that depends on them.© 2023. BioMed Central Ltd., part of Springer Nature.