Collaborative Research: Tipping points in coral reefs and their associated microbiomes: interactive effects of herbivory, nutrient enrichment, and temperature

珊瑚礁是地球上最多样化，但也是最危险的生态系统之一。全球变化导致了世界范围内珊瑚的减少，许多珊瑚礁现在缺乏珊瑚，并且被大型藻类所淹没。本研究探讨了热应激、重要草食性鱼类的过度捕捞和营养物污染等因素对珊瑚健康及其在大规模珊瑚杀伤干扰后的恢复能力的影响。重要的是，研究人员解决了全球变化对珊瑚微生物组的影响，这些微生物与珊瑚有关并影响珊瑚健康。最重要的假设是，过度捕捞和营养污染等因素通过影响珊瑚的微生物来影响珊瑚的健康。这项为期6年的实验是在法属波利尼西亚的Mo 'orea珊瑚礁上进行的，目的是研究当珊瑚礁暴露于升高的营养物质和海洋温度时，需要多少水平的食草动物（主要是鹦嘴鱼和刺尾鱼）来提供珊瑚及其微生物群的抵抗力和恢复力。值得注意的是，该团队测试了当地压力源（过度捕捞、营养污染）如何与全球压力源（气候变化和海洋温度上升）相互作用，从而影响珊瑚礁的健康。这项研究可能有助于了解如何管理当地因素（减少捕鱼，减轻营养污染），以帮助珊瑚在全球气候变化的压力下生存。实地试验提供了一个现实的平台来测试有关当地渔业管理如何改变珊瑚礁健康的问题，并提供了有关在实施新的水质管理后珊瑚礁恢复能力的数据。这项跨学科的工作培养了新一代的海洋生态学家和微生物学家，其中包括一名博士后研究员，两名研究生，以及众多本科生。主要的国际外联工作是绘制莫奥利亚岛的微生物群图。moorea的面积约为130平方公里，有五个主要分水岭，将沉积物和营养物质输送到近岸珊瑚礁生态系统。因此，对这些流域的管理不善可能导致目前在泻湖的几个地区发生的局部相移。因此，该团队与当地社区合作，帮助从岛上50个陆地、50个河流、25个沿海和25个近海地点收集微生物组样本。采样工作正在生成与土壤、溪流和沿海水域相关的全岛范围内的微生物群落地图，这些微生物群落可以与邻近的珊瑚礁健康联系起来——Moorea微生物组！作为推广工作的一部分，该团队还与电影制作人合作，制作了一部关于该项目的三语（英语、法语和大溪地语）电影，作为当地参与和教学工具，帮助学校团体和不同的利益相关者了解岛上陆地和海洋之间可见和不可见的联系。在法属波利尼西亚的莫奥利亚岛上，珊瑚群落表现出截然不同的轨迹，一些珊瑚礁从干扰中恢复过来，而另一些则经历了旷日持久的珊瑚衰退，同时伴随着大型藻类的增加。珊瑚群落动态的多样性使Mo 'orea成为一个很好的模型系统，用于测试为什么有些珊瑚礁具有弹性，并恢复到丰富的珊瑚，而另一些则没有，并经历持续的相移到大型藻类的优势。这项为期6年的实验将测量海底生物群落、珊瑚人口统计和珊瑚微生物组在海洋温度季节性变化中的动态，使团队能够(1)将珊瑚微生物组的变化（例如，致病菌的增加）与珊瑚衰退或恢复的轨迹联系起来；(2)将营养物质、草食和温度与底栖生物群落和珊瑚微生物组的相变联系起来。重要的是，该团队正在测试底栖生物群落和珊瑚微生物组在第三年底去除营养富集处理后的变化，并跟踪系统恢复3年以上，以此来测试它们对相移的抵抗力。因此，这个项目开始回答珊瑚礁和微生物群落的相移一旦发生是否可以很容易地逆转。许多研究都集中在分解珊瑚礁群落的因素上，但这是第一次研究如何从微生物组向上重新组装珊瑚礁群落。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Coral reefs are some of the most diverse, yet most imperiled, ecosystems on the planet. Global change has driven the decline of corals worldwide with many reefs now lacking corals and being overrun by macroalgae. This research examines the impacts of several factors of thermal stress, overfishing of important herbivorous fishes, and nutrient pollution on the health of corals and their ability to recover after large coral-killing disturbances. Importantly, the investigators address the impacts of global change on the coral microbiome, the microbes that associate with corals and impact coral health. The overarching hypothesis is that factors such as overfishing and nutrient pollution impact coral health via impacts to their microbes. This 6-year experiment on the coral reefs of Mo’orea, French Polynesia to examines what levels of herbivory, mostly by parrotfishes and surgeonfishes, are needed to provide resistance and resilience of corals and their microbiomes when reefs are exposed to elevated nutrients and ocean temperatures. Notably, the team tests how local stressors (overfishing, nutrient pollution) potentially interact with global stressors (climate change and rising ocean temperatures) to impact coral reef health. This research may yield insight into how to manage local factors (reducing fishing, mitigating nutrient pollution) to help corals survive the global stress of climate change. The field experiment provides a realistic platform to test questions about how local management of fisheries can alter reef health and provides data about the recoverability of reefs should new water quality management be put into place. This interdisciplinary work trains a new generation of both marine ecologists and microbiologists, including one postdoctoral researcher, two graduate students, as well as numerous undergraduates. The main international outreach effort is to map the microbiome of the island of Mo’orea. Mo’orea is approximately 130 square-kilometers in area and has five major watersheds that transport sediment and nutrients to the nearshore coral reef ecosystems. Thus poor stewardship of these watersheds likely contributes to the local phase shifts currently occurring in several areas of the lagoon. Therefore the team has engaged the local community to help collect microbiome samples from 50 terrestrial, 50 stream, 25 coastal sites, and 25 offshore sites around the island. The sampling effort is generating an island-wide map of the microbial communities associated with the soils, streams, and coastal waters that can be linked to adjacent coral reef health - The Moorea Microbiome! As part of this outreach effort, the team also collaborates with filmmakers to make a trilingual (English, French, and Tahitian) film about the project to serve as local engagement and teaching tool to help educate school groups and different stakeholders about both the seen and unseen connections between land and sea on their island. On the island of Mo’orea, French Polynesia, coral communities have exhibited strikingly different trajectories, with some reefs recovering from disturbances and others undergoing protracted coral decline, accompanied by an increase in macroalgae. This diversity in coral community dynamics makes Mo’orea an excellent model system for testing why some reefs are resilient and return to abundant coral while others are not and undergo persistent phase shifts to macroalgal dominance. This 6-year experiment will measure the dynamics of benthic communities, coral demography, and the coral microbiome across seasonal change in ocean temperature, allowing the team to (1) link changes in coral microbiomes (e.g., a rise in pathogenic bacteria) to the trajectories of coral decline or recovery and (2) link nutrients, herbivory, and temperature to phase shifts in both benthic communities and coral microbiomes. Importantly, the team is testing the resistance of phase shifts of benthic communities and coral microbiomes by measuring their changes after removing the nutrient enrichment treatment at the end of year 3 and tracking recovery of the system for 3 more years. Thus, this project begins to answer whether reef and microbial community phase shifts can be easily reversed once they occur. Many studies have focused on the factors that disassemble coral reef communities, but this is the first to examine how reef communities can be reassembled from the microbiome upwards.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.