Steinberg Rosemary K, Ainsworth Tracy D, Moriarty Tess, Bednarek Teresa, Dafforn Katherine A, Johnston Emma L
Evolution and Ecology Research Centre and Centre for Marine Science and Innovation, School of Biological, Earth, and Environmental Sciences, Faculty of Science, University of New South Wales, Sydney, NSW, Australia.
Sydney Institute of Marine Science, Mosman, NSW, Australia.
Front Physiol. 2022 May 19;13:804193. doi: 10.3389/fphys.2022.804193. eCollection 2022.
Coral reefs are amongst the most biodiverse ecosystems on earth, and while stony corals create the foundational complexity of these ecosystems, octocorals and anemones contribute significantly to their biodiversity and function. Like stony corals, many octocorals contain Symbiodiniaceae endosymbionts and can bleach when temperatures exceed the species' upper thermal limit. Here, we report octocoral bleaching susceptibility and resistance within the subtropical Lord Howe Island coral reef ecosystem during and after marine heatwaves in 2019. Octocoral and anemone surveys were conducted at multiple reef locations within the Lord Howe Island lagoon during, immediately after, and 7 months after the heatwaves. One octocoral species, sp. 1, experienced bleaching and mortality, with some bleached colonies detaching from the reef structure during the heatwave (presumed dead). Those that remained attached to the benthos survived the event and recovered endosymbionts within 7 months of bleaching. sp. 1 Symbiodiniaceae density (in cells per µg protein), chlorophyll and per µg protein, and photosynthetic efficiency were significantly lower in bleached colonies compared to unbleached colonies, while chlorophyll and per symbiont were higher. Interestingly, no other symbiotic octocoral species of the Lord Howe Island lagoonal reef bleached. Unbleached cf colonies had higher Symbiodiniaceae and chlorophyll densities during the marine heatwave compared to other monitoring intervals, while sp. 2 densities did not change substantially through time. Previous work on octocoral bleaching has focused primarily on gorgonian octocorals, while this study provides insight into bleaching variability in other octocoral groups. The study also provides further evidence that octocorals may be generally more resistant to bleaching than stony corals in many, but not all, reef ecosystems. Responses to marine heating events vary and should be assessed on a species by species basis.
珊瑚礁是地球上生物多样性最丰富的生态系统之一。虽然石珊瑚构成了这些生态系统的基础复杂性，但八放珊瑚和海葵对其生物多样性和功能也有重要贡献。与石珊瑚一样，许多八放珊瑚含有共生藻内共生体，当温度超过物种的热上限时会发生白化。在此，我们报告了2019年海洋热浪期间及之后，亚热带豪勋爵岛珊瑚礁生态系统中八放珊瑚的白化易感性和抗性。在热浪期间、热浪刚结束后以及热浪结束7个月后，对豪勋爵岛泻湖内多个珊瑚礁地点进行了八放珊瑚和海葵调查。一种八放珊瑚物种，物种1，经历了白化和死亡，一些白化的群体在热浪期间从珊瑚礁结构上脱落（推测已死亡）。那些仍附着在底栖生物上的群体在事件中存活下来，并在白化后7个月内恢复了内共生体。与未白化的群体相比，白化群体中的物种1共生藻密度（每微克蛋白质中的细胞数）、叶绿素a和叶绿素c每微克蛋白质含量以及光合效率显著降低，而每个共生体内的叶绿素a和叶绿素c含量更高。有趣的是，豪勋爵岛泻湖珊瑚礁的其他共生八放珊瑚物种没有白化。与其他监测时期相比，未白化的cf群体在海洋热浪期间共生藻和叶绿素密度更高，而物种2的密度随时间变化不大。先前关于八放珊瑚白化的研究主要集中在柳珊瑚八放珊瑚上，而本研究提供了对其他八放珊瑚群体白化变异性的见解。该研究还提供了进一步的证据，表明在许多但并非所有的珊瑚礁生态系统中，八放珊瑚通常可能比石珊瑚更耐白化。对海洋升温事件的反应各不相同，应逐种进行评估。
