CAREER: Fish-derived nutrients in a coral reef ecosystem - impacts on benthic communities and importance for coral restoration

珊瑚礁目前正受到各种人为威胁的危害，这些威胁包括气候变化、珊瑚疾病、对重要鱼类的过度捕捞以及营养物质的过量富集。这些威胁会导致珊瑚和鱼类的减少和海藻的增加，将珊瑚礁变成海藻礁。了解人类介导的变化如何影响珊瑚礁生态的一个重要方面是了解鱼类如何影响珊瑚礁的重要营养循环。研究人员先前的研究表明，鱼类可能是通过其日常排泄的氮和磷在珊瑚礁上最重要的来源之一。这些鱼类来源的营养物质可以帮助珊瑚生长得更快，但如果珊瑚被气候变化或疾病等其他过程杀死，也可以帮助海藻生长得更快。然而，来自人类来源的营养物质，例如农业径流或污水排放，可能对珊瑚有害，因为这些营养物质通常与鱼类排泄物中的营养物质不同。研究人员试图了解鱼类来源与人类来源的营养物质对珊瑚生长、海藻生长的不同影响，并最终影响珊瑚礁生态系统的健康。这项研究还将促进一些培训和外展机会，包括：(1)培养研究生和本科生，(2)在FIU和MAST@FIU（一所新兴的科技磁铁高中）之间建立伙伴关系，对未被充分代表的少数民族进行海洋生物学教育，(3)通过广泛分发的视频向大众传播海洋科学，以及(4)创建一个公民科学计划，让感兴趣的海洋生物学学生参与帮助监督一些实地实验。此外，这项工作将为珊瑚礁恢复科学提供急需的信息。珊瑚礁的恢复是一个不断发展的领域，但许多恢复工作在了解保持珊瑚礁健康的生态过程方面缺乏坚实的基础。因此，这项工作将能够对教育管理人员和修复从业者了解有助于促进成功修复工作的过程作出重大贡献。这项研究将解决鱼类的营养排泄如何影响珊瑚礁群落的基本和未经测试的问题。先前的数据表明，珊瑚礁的生态与鱼类作为有限营养物质的提供者的作用密切相关，因为鱼类是珊瑚礁上氮的来源之一，如果不是最重要的来源。这项研究不仅范围独特，而且恰逢其时，因为珊瑚礁面临着全球性的威胁。由于过度捕捞剥夺了重要的鱼类（以及它们作为营养提供者的角色），而人为的营养负荷增加了潜在有害营养物质的丰富程度，珊瑚礁上的营养状况可能会变得更糟。该项目的目标是量化鱼类排泄物中的营养物质如何影响珊瑚礁群落结构，以及这种影响在不同的环境背景下是如何变化的。具体来说，研究者概述了研究的重点，将在美国佛罗里达群岛的珊瑚礁上实现三组一般目标：(1)评估鱼类来源的营养物质如何影响珊瑚礁内外的底栖生物群落结构和珊瑚生长和健康，以及这种影响如何随非生物环境而变化；(2)测试个别珊瑚和藻类的生理和生长如何对鱼类排泄中的不同营养来源与人为营养负荷作出反应；(3)研究鱼类来源的营养物质如何影响珊瑚的恢复，以及如何设计恢复方案，以利用鱼类来源的营养物质对珊瑚生长的重要作用。这些问题将通过：(1)现场监测计划（目标1），(2)机械营养富集实验（目标2）和(3)珊瑚恢复实验（目标3）来解决。

Coral reefs are currently imperiled from a variety of human-induced threats from climate change, coral diseases, overexploitation of important fish species, and enrichment with excessive amounts of nutrients. These threats can result in the decline in corals and fishes and the rise in seaweeds, turning coral reefs into seaweed reefs. One important aspect of understanding how human-mediated changes impact the ecology of reefs is to understand how fishes impact important nutrient cycles on reefs. The investigators prior research suggests that fishes may be one of the most important sources of nitrogen and phosphorus on reefs via their daily excretions. These fish-derived nutrients may help corals grow faster but could also help seaweeds grow faster if corals are killed by other processes such as climate change or disease. However, nutrients from human-derived sources such as runoff from agriculture or sewage discharge can be harmful to corals as these nutrients are often of different types than those in fish excretions. The investigator seeks to understand how the different effects of fish-derived vs. human-derived nutrients impact coral growth, seaweed growth, and, ultimately, the health of coral reef ecosystems. This research will also facilitate a number of training and outreach opportunities including: (1) training graduate and undergraduate students, (2) creating a partnership between FIU and MAST@FIU, a new science and technology magnet high school, to educate underrepresented minorities in marine biology, (3) taking marine science to the masses with widely distributed videos, and (4) creating a citizen science initiative that will get interested marine biology students involved with helping to monitor some of the field experiments. Further, this work will generate much needed information on the science of coral reef restoration. Restoration of reefs is a growing field but many restoration efforts have little solid grounding in understanding the ecological processes that keep reefs healthy. Thus, this work will be able to make significant contribution to educating managers and restoration practitioners as to the processes that can help facilitate successful restoration efforts.This research will address fundamental and untested questions of how nutrient excretion by fishes impacts coral reef communities. Prior data suggest that the ecology of reefs is critically linked to the role of fishes as providers of limiting nutrients since fishes are one of, if not the most important, sources of N on reefs. This research is not only unique in its scope but also timely due to the global threats to reefs. As overfishing removes important fishes (and their role as nutrient providers) and anthropogenic nutrient loading increases the abundance of potentially harmful nutrients, the nutrient regimes on reefs may be changing for the worse. The goal of this project is to quantify how nutrients from fish excretion impact coral reef community structure and how this effect varies across environmental context. Specifically, the investigator outlines research to focus on three general sets of objectives that will be approached on reefs in the Florida Keys, USA: (1) Assess how fish-derived nutrients influence benthic community structure and coral growth and health both across and within reefs and how this influence varies with abiotic context, (2) Test how the physiology and growth of individual corals and algae respond to the different nutrient sources in fish excretion vs. anthropogenic nutrient loading, and (3) Examine how fish-derived nutrients impact coral restoration and how to design restoration programs to take advantage of important of fish-derived nutrients for coral growth. These questions will be addressed with: (1) a field monitoring program (Objective 1), (2) mechanistic nutrient enrichment experiments (Objective 2), and (3) coral restoration experiments (Objective 3).