RUI: Collaborative Research: Defining the biogeochemical context and ecological impacts of submarine groundwater discharge on coral reefs

海底地下水排放(SGD)是水从陆地流经沿海海底进入附近海洋的过程。每年大约有13,000立方千米的地下水被排放到沿海环境中，然而这种新鲜的、往往营养丰富的SGD对珊瑚礁的影响仍然知之甚少。这一SGD投入是由降水、人类土地利用、海平面上升、潮汐幅度和地下水使用的变化驱动的，其中许多变化正随着气候和人类影响而迅速变化。这个项目提高了我们对SGD对珊瑚礁影响的理解，以更好地预测自然和人类诱导的变化将如何影响未来沿海生态系统的功能。该项目在太平洋研究最广泛的珊瑚礁生态系统之一(法属波利尼西亚的莫雷亚，莫雷亚珊瑚礁生态系统LTER的所在地)工作；该项目测试SGD对个人、社区和生态系统规模的珊瑚礁过程的影响。利用定量研究、笼养实验和合成模型，研究人员：1)表征SGD梯度，并将其与高分辨率珊瑚礁覆盖数据联系起来；2)确定SGD如何影响个体到生态系统的过程；3)开发一个合成模型，说明SGD通量的变化将如何改变珊瑚礁生态系统功能。由于SGD是世界各地近岸珊瑚礁的共同特征，这项研究的结果对理解珊瑚礁的表现具有全球影响，珊瑚礁是重要的经济、文化和科学资源。该项目旨在提供跨越多个职业层次的培训，包括13名本科生、2名研究生、2名高级人员、1名博士后研究员、1名女性初任首席调查员和2名高级合作调查员，重点是鼓励代表不足的群体参与(例如，通过阿拉斯加原住民和夏威夷原住民、亚裔美国人和原住民太平洋岛民以及加州州立大学北岭分校、夏威夷大学M&amp；#257；Noa和加州州立大学长滩分校的拉美裔服务机构)。研究人员与莫雷亚当地的K-12学生和教师合作，并与一位常驻艺术家合作，通过在莫雷亚、迈阿密和洛杉矶的互动和身临其境的艺术体验，向更广泛的公众传播科学。SGD是许多近岸珊瑚礁生态系统的一种自然且未被研究的特征，可对海洋生物地球化学产生重大变化，并对造礁珊瑚、大型藻类和生物爬行动物等沿海生物产生影响。SGD可能在珊瑚礁生态系统功能中发挥关键作用，因为它改变了关键的物理化学参数(例如，温度、盐度、营养物质和碳酸盐化学)，这些参数对珊瑚礁上的生物和非生物过程都有很大影响。该项目(I)描述了法属波利尼西亚莫雷亚SGD的空间范围和生物地球化学信号，(Ii)确定SGD如何影响微生物过程、底栖生物生长速率和生理学、珊瑚、大型藻类和草食动物之间的物种相互作用以及净生态系统钙化和生产率，以及(Iii)通过综合模拟工作定量评估SGD通量的变化将如何改变珊瑚礁生物地球化学和生态系统功能。具体地说，本研究收集的水文地质、生物地球化学和生态数据采用贝叶斯结构方程模型进行综合。该项目描述和量化了SGD如何通过生物地球化学的变化和个体对生态系统反应的改变直接和间接地影响生态系统功能，从而提供了更好的跟踪和预测珊瑚礁生态系统功能变化的能力。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。

Submarine groundwater discharge (SGD) is the flow of water from land through the coastal seafloor into the nearby ocean. Approximately 13,000 cubic kilometers of groundwater is discharged into coastal environments every year, yet the effects of this fresh and often nutrient rich SGD are still poorly understood for coral reefs. This SGD input is driven by changes in precipitation, human land use, sea-level rise, tidal amplitude, and groundwater usage, many of which are rapidly changing with climate and human impacts. This project improves our understanding of SGD effects on coral reefs to better predict how both natural and human-induced changes will affect coastal ecosystem functioning in the future. Working in one of the most comprehensively studied coral reef ecosystems in the Pacific (Mo'orea, French Polynesia, home of the Mo'orea Coral Reef Ecosystem LTER); this project tests the influence of SGD on individual, community, and ecosystem-scale coral reef processes. Using mensurative studies, caging experiments, and a synthetic model, the investigators: 1) characterize SGD gradients and relate it to high resolution coral reef cover data, 2) determine how individual to ecosystem processes are influenced by SGD, and 3) develop a synthetic model to show how changes in SGD fluxes will alter reef ecosystem functioning. As SGD is a common feature on nearshore coral reefs worldwide, the results of this study have global implications for understanding the performance of coral reefs, which are essential economic, cultural, and scientific resources. This project is structured to provide training across multiple career levels, linking 13 undergraduate students, 2 graduate students, 2 senior personnel, 1 postdoctoral researcher, 1 female beginning lead investigator, and 2 senior co-investigators, with a focus on encouraging participation from underrepresented groups (e.g., through the Alaska Native and Native Hawaiian, Asian American and Native American Pacific Islander, and Hispanic-Serving Institutions of California State University Northridge, the University of Hawaiʻi at Mānoa, and California State University Long Beach). The investigators work with local K-12 students and teachers in Mo'orea and collaborate with an artist-in-residence to communicate science to the broader public through interactive and immersive art experiences in Mo'orea, Miami, and Los Angeles. SGD is a natural and understudied feature of many nearshore coral reef ecosystems, which can contribute substantial changes to marine biogeochemistry, with impacts for coastal organisms such as reef-building corals, macroalgae, and bioeroders. SGD may play a key role in coral reef ecosystem functioning because it alters key physicochemical parameters (e.g., temperature, salinity, and nutrient and carbonate chemistry) that substantially affect both biotic and abiotic processes on coral reefs. This project (i) characterizes the spatial extent and biogeochemical signal of SGD in Mo'orea, French Polynesia, (ii) identifies how SGD influences microbial processes, benthic organism growth rates and physiology, species interactions between corals, macroalgae, and herbivores, and net ecosystem calcification and production rates, and (iii) quantitatively assesses how changes in SGD fluxes will alter reef biogeochemistry and ecosystem functioning through an integrative modelling effort. Specifically, the hydrogeological, biogeochemical, and ecological data collected in this study are synthesized in a Bayesian structural equation model. This project characterizes and quantifies how SGD directly and indirectly affects ecosystem functioning via changes in biogeochemistry and altered individual to ecosystem responses, thereby providing a better capacity to track and predict alterations in reef ecosystem function.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.