Cascading interactions of herbivore loss and nutrient enrichment on coral reef macroalgae, corals, and microbial dynamics

加勒比海的珊瑚礁正在经历前所未有的珊瑚覆盖率下降，这在很大程度上是由于气候变化，污染以及鱼类生物多样性和丰度的减少。大型藻类在珊瑚礁上变得丰富，可能是由于食草动物的减少（例如，过度捕捞）和人为输入的营养物质增加。大型藻类的扩散对珊瑚礁的恢复有负面的反馈作用，因为藻类往往是上级竞争对手，抑制成年和幼年珊瑚的生长。迄今为止，大多数珊瑚礁研究都集中在压力源如何影响大型生物，而相对较少的研究如何这些压力源和由此产生的藻类占主导地位的国家影响微生物。然而，珊瑚礁相关微生物通过生物地球化学循环和疾病在珊瑚礁生态系统中发挥着重要作用。由于微生物是珊瑚的重要共生体，也是潜在的病原体，重要的是要了解控制其分类和功能多样性的机制。本提案的目标是量化自上而下的改变（清除草食性鱼类）和自下而上（无机营养物添加）的力量改变macrobial以及微生物对珊瑚礁的动力学，以了解机制，加强珊瑚-深海礁系统本研究提出了两个主要问题：Q1。养分富集和食草动物的清除如何相互作用，影响底栖藻类丰度、珊瑚-藻类相互作用以及珊瑚的生存和生长？Q2.营养富集和草食动物的去除如何影响珊瑚上和珊瑚内的细菌丰度、分类多样性和功能多样性？拟议的研究将直接和经验解决许多目前的假设，自下而上和自上而下的力量如何改变珊瑚礁动态。PI将调查：（1）多年来多种压力源的影响;（2）对生物组织多个层次的影响（从鱼类到藻类再到微生物）;（3）藻类-珊瑚微生物相互作用变化的机制。值得注意的是，这种方法将提供必要的统计能力，以区分季节性和压力引起的宏观和微生物多样性的变化。拟议的工作是实验生态学和微生物学的独特结合，将提高我们评估全球珊瑚礁威胁的能力。培训将包括一名博士后研究员，一名研究生和两名海洋生态学，微生物共生和分子生物学领域的本科生。该项目还将为本科少数民族学生提供研究机会，因为FIU是美国最大的少数民族和城市服务机构之一，超过70%的学生来自科学领域代表性不足的群体（59%西班牙裔，13%黑人，4%亚洲人; 56%女性）。 PI还致力于在地方和国家层面上开展大学以外的强有力的外展计划。例如，他们建立了每月一次的科学咖啡馆（“吃，想，快乐！“）在一家独立的迈阿密书店，为公众提供一个休闲的环境，让他们与当地科学家聚在一起，了解和讨论影响佛罗里达沃茨的科学和保护主题。他们还与Symbio工作室合作，为霍顿米夫林哈考特的科学融合项目制作关于珊瑚礁生态系统的视频。

Coral reefs in the Caribbean Sea are undergoing unprecedented declines in coral cover due in large part to climate change, pollution, and reductions in fish biodiversity and abundance. Macroalgae have become abundant on reefs, probably due to decreases in herbivory (e.g., through overfishing) and increases in anthropogenic inputs of nutrients. The spread of macroalgae has negative feedbacks on reef recovery because algae are often superior competitors and suppress growth of both adult and juvenile corals. A majority of reef studies to date have focused on how stressors affect macroorganisms, while relatively few have investigated how these stressors and the resultant algal-dominated states affect microorganisms. Yet, coral reef-associated microbes play significant roles in coral reef ecosystems through biogeochemical cycling and disease. Since microbes are important mutualists of corals as well as potential pathogens, it is important to understand the mechanisms that control their taxonomic and functional diversity.The goal of this proposal is to quantify how alterations of top-down (removal of herbivorous fish) and bottom-up (inorganic nutrient addition) forces alter macrobial as well as microbial dynamics on coral reefs in order to understand the mechanisms that reinforce coral-depauperate reef systems. This work asks two main questions:Q1. How do nutrient enrichment and herbivore removal interact to affect benthic algal abundance, coral-algal interactions, and coral survivorship and growth?Q2. How do nutrient enrichment and herbivore removal affect bacterial abundance, taxonomic diversity, and functional diversity on and within corals?The proposed research will directly and empirically address many of the current hypotheses about how bottom-up and top-down forces alter reef dynamics. The PIs will investigate: (1) the impact of multiple stressors over several years; (2) impacts on multiple levels of biological organization (from fishes to algae to microbes); and (3) the mechanisms underlying changes in algal-coral microbe interactions. Significantly, the approach will provide the statistical power necessary to distinguish between seasonal- and stress-induced changes in macro- and microbial diversity. The proposed work is a unique combination of experimental ecology and microbiology that will improve our ability to evaluate global threats to reefs. Training will include a postdoctoral researcher, a graduate student, and two undergraduates in the fields of marine ecology, microbial symbiosis, and molecular biology. The project will also provide research opportunities for undergraduate minority students, since FIU is one of the largest minority and urban-serving institutions in the US, with over 70% of its students from under-represented groups in science (59% Hispanic, 13% Black, 4% Asian; 56% female). The PIs are also committed to strong outreach programs outside their university at both the local and national levels. For example, they have established a monthly science café ("Eat, Think, and Be Merry!") at an independent Miami bookstore to provide a casual environment for the public to come together with local scientists to learn about and discuss science and conservation topics that impact Florida waters. They are also collaborating with Symbio Studios to produce videos on coral reef ecosystems for their educational series for Houghton Mifflin Harcourt's Science Fusion programs.