School of Marine Science and Policy, University of Delaware, Lewes, DE, United States.
GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany.
Sci Rep. 2019 Jul 10;9(1):9985. doi: 10.1038/s41598-019-46412-4.
High sea surface temperatures often lead to coral bleaching wherein reef-building corals lose significant numbers of their endosymbiotic dinoflagellates (Symbiodiniaceae). These increasingly frequent bleaching events often result in large scale coral mortality, thereby devasting reef systems throughout the world. The reef habitats surrounding Palau are ideal for investigating coral responses to climate perturbation, where many inshore bays are subject to higher water temperature as compared with offshore barrier reefs. We examined fourteen physiological traits in response to high temperature across various symbiotic dinoflagellates in four common Pacific coral species, Acropora muricata, Coelastrea aspera, Cyphastrea chalcidicum and Pachyseris rugosa found in both offshore and inshore habitats. Inshore corals were dominated by a single homogenous population of the stress tolerant symbiont Durusdinium trenchii, yet symbiont thermal response and physiology differed significantly across coral species. In contrast, offshore corals harbored specific species of Cladocopium spp. (ITS2 rDNA type-C) yet all experienced similar patterns of photoinactivation and symbiont loss when heated. Additionally, cell volume and light absorption properties increased in heated Cladocopium spp., leading to a greater loss in photo-regulation. While inshore coral temperature response was consistently muted relative to their offshore counterparts, high physiological variability in D. trenchii across inshore corals suggests that bleaching resilience among even the most stress tolerant symbionts is still heavily influenced by their host environment.
高海表温度通常会导致珊瑚白化，造礁石珊瑚会失去大量共生的虫黄藻（Symbiodiniaceae）。这些越来越频繁的白化事件往往会导致大规模珊瑚死亡，从而破坏世界各地的珊瑚礁系统。帕劳周围的珊瑚礁生境非常适合研究珊瑚对气候干扰的反应，与近海的堡礁相比，许多近岸海湾的水温更高。我们研究了四种常见的太平洋珊瑚物种（Acropora muricata、Coelastrea aspera、Cyphastrea chalcidicum 和 Pachyseris rugosa）中各种共生虫黄藻对高温的 14 种生理特性，这些珊瑚物种存在于近海和近岸生境中。近岸珊瑚主要由单一的耐受压力的共生体 Durusdinium trenchii 组成，但共生体的热响应和生理学在不同的珊瑚物种之间有显著差异。相比之下，近海珊瑚中存在特定的 Cladocopium spp.（ITS2 rDNA 型-C），但当加热时，所有这些珊瑚都经历了相似的光灭活和共生体丧失模式。此外，加热后的 Cladocopium spp. 细胞体积和光吸收特性增加，导致光调节能力下降。虽然近岸珊瑚的温度响应相对于近海珊瑚来说一直较为缓和，但 D. trenchii 在近岸珊瑚中的高生理变异性表明，即使是最耐受压力的共生体的白化恢复能力仍然受到其宿主环境的严重影响。
