RAPID: Ecosystem impact of a coral bleaching event: The role of coral exudates in shifting oligotrophic biogeochemistry and reef microbiomes.

浅海热带珊瑚礁是生物多样性的热点地区。它们的生态系统服务使它们成为具有经济、生态和文化重要性的关键领域。然而，由于局部和全球压力，珊瑚礁正受到严重威胁，这可能导致珊瑚漂白、疾病，并最终导致珊瑚死亡。当珊瑚漂白时，它们会释放出可能影响整个生态系统的物质，如死亡组织、粘液、细菌和病毒。该项目使用在法属波利尼西亚长期生态研究地点的一次广泛的漂白事件来探索这些释放的物质如何影响珊瑚礁生态系统，检查与珊瑚和周围水域相关的水化学和微生物。这项研究旨在更好地了解珊瑚如何与环境相互作用，以及当珊瑚受到压力时，这种相互作用是如何变化的。在整个项目中，两名女研究生正在接受培训，并使用互动程序将结果传达给俄勒冈州的小学、高中和本科生。一部20分钟的网络纪录片正在与电影学生一起准备，重点是珊瑚漂白对珊瑚礁规模的影响。珊瑚渗出物包括颗粒和溶解物质(松弛的组织、粘液、细菌、病毒)，这些物质共同向珊瑚礁添加有限的营养物质和碳化合物，促进自养和异养细菌的产生。在最近的实验中，观察到珊瑚漂白衍生的渗出物本身就会导致先前健康的珊瑚迅速漂白，甚至经常死亡。重要的是，暴露在珊瑚渗出物中的这些负面影响远远大于热应激。这些实验提供了一种新的机制，在这种机制中，漂白的珊瑚会对邻近珊瑚的健康产生不利影响。该项目利用这些数据和莫雷亚岛上正在进行的广泛的白化事件来量化珊瑚渗出物对珊瑚礁生态系统的级联影响。假设在大范围的漂白过程中：(1)珊瑚礁的DOC显著升高；(2)珊瑚全离子组分在远洋微生物群中变得丰富；(3)水体微生物群落的功能转变为异养性和致病性增加；(4)珊瑚全磷偏离其先前的稳定状态，导致珊瑚礁生物失调和/或疾病和死亡。在莫雷亚正在进行的漂白事件的整个过程中的采样被用来量化该漂白事件对DOM动态和珊瑚礁健康的影响。莫雷亚位于MCR长期生态研究(MCR LTER)场地内。在这个经过充分研究的地点发生了罕见的珊瑚礁规模的白化事件，这为量化珊瑚渗出物对珊瑚礁健康的影响和更好地了解贫营养生态系统中全岛白化事件的时间和空间影响提供了不同寻常的机会。在珊瑚礁生态系统随时间和空间被很好地参数化的岛屿上，通过测量单位面积珊瑚释放的有机物质的数量，可以开发出漂白事件对岛屿碳预算的影响的模型。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Shallow tropical reefs are biodiversity hotspots. Their ecosystem services make them key areas of economic, ecological, and cultural importance. Yet coral reefs are under significant threat due to both local and global stressors which can lead to coral bleaching, disease, and eventually coral death. When corals bleach, they release materials such as dead tissue, mucus, bacteria, and viruses that may affect the entire ecosystem. This project uses a wide-spread bleaching event at a Long Term Ecological Research site in French Polynesia to explore how these released materials impact the reef ecosystem The water chemistry and microbes associated with the corals and surrounding water are examined. This research aims to better understand how corals interact with their environment and how this interaction changes when corals are stressed. Throughout this project two female graduate students are being trained and interactive programs are used to communicate results to elementary, high school, and undergraduate students in Oregon. A 20-minute documentary for web release focusing on the reef scale impact of coral bleaching is in preparation together with film students.Coral exudates include particulate and dissolved material (sloughed tissue, mucus, bacteria, viruses) that together add limiting nutrients and carbon compounds to the reef, fueling auto- and heterotrophic bacterial production. In recent experiments, coral-bleaching derived exudates were observed to themselves cause rapid bleaching, and often mortality, of previously healthy corals. Importantly, these negative impacts of coral exudate exposure were far greater than thermal stress. These experiments provided insight into a novel mechanism in which bleaching corals can adversely affect the health of adjacent corals. This project leverages these data and an extensive and ongoing bleaching event on the island of Mo?orea to quantify the cascading effects of coral exudates on reef ecosystems. It is hypothesized that during widespread bleaching: (1) DOC is significantly elevated across the reefscape; (2) coral holobiont components become enriched in the pelagic microbiome; (3) the water column microbial community shifts in function to increased heterotrophy and pathogenicity; and (4) coral holobionts diverge from their previous stable state leading to coral reef dysbiosis and/or disease and mortality. Sampling throughout the course of an ongoing bleaching event in Mo?orea is used to quantify the effects of this bleaching event on DOM dynamics and reef health. Mo'orea is situated in the MCR Long Term Ecological Research (MCR LTER) site. The rare reef-scale bleaching event at this well-studied location provides the unusual opportunity to quantify the impact of coral exudates on reef health and to better understand the temporal and spatial impacts of an island-wide bleaching event in an oligotrophic ecosystem. Measurement of the amount of organic matter released per unit area of coral on an island where the reef ecosystem is well parameterized over time and space allows development of a model of the impact of bleaching events on the island carbon budget.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.