Coral reefs are undergoing degradation due to overexploitation, pollution, and climate change. Management and restoration efforts require that we gain a better understanding of the complex interactions between corals, their microbiomes, and their environment. For this purpose, Varadero Reef near Cartagena, Colombia, serves as an informative study system located at the entrance of the Bay of Cartagena adjacent to the Canal del Dique, which carries turbid and polluted water into the bay. Varadero’s survival under poor environmental conditions makes it a great study site for investigating the relationship between the microbiome and coral resistance to environmental stressors. To determine whether the microbiomes of Varadero corals differ from those in less impacted sites, we conducted a reciprocal transplant experiment by relocating coral fragments from Varadero as well as a geographically proximate reef that is less affected by plume dynamics (Rosario) across a gradient of turbidity (low, medium, and high). After 6 months of acclimatization, transplanted corals developed site-specific microbiomes that differed significantly from pre-transplant microbiomes, and corals transplanted to the highly impacted site from both Varadero and Rosario site saw higher mortality and an increase in overall microbial diversity. In combination with physiology and survivorship outcomes pointing to a limit in the corals’ photoacclimative capacity, our results indicate that, rather than surviving, Varadero Reef is experiencing a slow decline, and its corals are likely on the brink of dysbiosis. With continued anthropogenic interference in marine environments, sites such as Varadero will become increasingly common, and it is imperative that we understand how corals and their microbial symbionts are changing in response to these new environmental conditions.

中文翻译：

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生存边缘化珊瑚礁：评估微生物组对珊瑚生理和生存的影响

由于过度开发、污染和气候变化，珊瑚礁正在退化。管理和恢复工作要求我们更好地了解珊瑚、它们的微生物群和它们的环境之间复杂的相互作用。为此，哥伦比亚卡塔赫纳附近的巴拉德罗礁作为信息研究系统，位于卡塔赫纳湾入口处，毗邻迪克运河，将浑浊和污染的水带入海湾。巴拉德罗在恶劣环境条件下的生存使其成为研究微生物组与珊瑚对环境压力因素的抵抗力之间关系的绝佳研究地点。为了确定巴拉德罗珊瑚的微生物群落是否与受影响较小地点的微生物群落不同，我们通过重新定位来自巴拉德罗的珊瑚碎片以及地理上邻近的珊瑚礁进行了互惠移植实验，该珊瑚礁在浊度梯度（低、中和高）中受羽流动力学 (Rosario) 的影响较小。在适应 6 个月后，移植的珊瑚形成了与移植前微生物组显着不同的特定地点的微生物组，从巴拉德罗和罗萨里奥地点移植到受影响严重的地点的珊瑚死亡率更高，整体微生物多样性增加。结合生理学和生存结果表明珊瑚的光适应能力有限，我们的结果表明，巴拉德罗礁不是幸存下来，而是正在经历缓慢衰退，其珊瑚可能处于生态失调的边缘。