Abstract：
The frequency and severity of marine heatwaves causing mass mortality events in tropical and temperate coral species increases every year, with serious consequences on the stability and resilience of coral populations. Although recovery and persistence of coral populations after stress events is closely related to adult fitness, as well as larval survival and settlement, much remains unknown about the effects of thermal stress on early life-history stages of temperate coral species. In the present study, the reproductive phenology and the effect of increased water temperature (+4°C and +6°C above ambient, 20°C) on larval survival and settlement was evaluated for two of the most representative Mediterranean octocoral species (Eunicella singularis and Corallium rubrum). Our study shows that reproductive behavior is more variable than previously reported and breeding period occurs over a longer period in both species. Thermal stress did not affect the survival of symbiotic E. singularis larvae but drastically reduced the survival of the non-symbiotic C. rubrum larvae. Results on larval biomass and caloric consumption suggest that higher mortality rates of C. rubrum exposed to increased temperature were not related to depletion of endogenous energy in larvae. The results also show that settlement rates of E. singularis did not change in response to elevated temperature after 20 days of exposure, but larvae may settle fast and close to their native population at 26°C (+6°C). Although previous experimental studies found that adult colonies of both octocoral species are mostly resistant to thermal stress, our results on early life-history stages suggest that the persistence and inter-connectivity of local populations may be severely compromised under continued trends in ocean warming.
摘要：
海洋热浪在热带和温带珊瑚物种中造成大规模死亡事件的频率和严重程度每年都在增加，对珊瑚种群的稳定和复原力造成严重后果。尽管应激事件后珊瑚种群的恢复和持续与成人健康密切相关，以及幼虫的生存和定居，关于热应激对温带珊瑚物种早期生活史阶段的影响，还有很多未知。在本研究中,生殖物候和水温升高的影响(高于环境温度+4°C和+6°C，20°C）对两种最具代表性的地中海八珊瑚物种（单珊瑚和红珊瑚）的幼虫存活和定居进行了评估。我们的研究表明，生殖行为比以前报道的更加多变，并且两个物种的繁殖期都在更长的时间内发生。热胁迫不会影响共生的奇异性C.singularis幼虫的存活，但大大降低了非共生的红色C.rubrum幼虫的存活。有关幼虫生物量和热量消耗的结果表明，暴露于温度升高的红色念珠菌的较高死亡率与幼虫内源性能量的消耗无关。结果还表明，暴露20天后，奇异大肠杆菌的沉降率没有因温度升高而变化，但是幼虫在26°C（6°C）时可能会快速沉降并接近其本地种群。尽管以前的实验研究发现，两种八珊瑚的成年菌落大多对热应力具有抵抗力，我们对早期生活史阶段的研究结果表明,在海洋变暖的持续趋势下,当地人口的持久性和相互连通性可能会受到严重损害.
