Fish aggregations and biogeochemical hot spots across regional environmental gradients

长期以来，海洋生态系统的消费者因其在自上而下调节生态系统中的作用而得到承认，但他们通过营养供应等自下而上途径产生的影响往往被低估，也没有被纳入沿海生态系统动态模型。然而，当消费者聚集时，来自消费者的营养供应可能是一个调节因素，例如鱼类在结构复杂的栖息地周围。研究这一自下而上的机制路径对于更全面地了解海草生态系统至关重要，因为海草生态系统在全球范围内很重要，也受到威胁。这项研究将解决以下问题：(1)消费者的集中营养供应是否会导致海草床层出现明显的生物地球化学热点？以及(2)消费者对生态系统过程的影响如何在养分可获得性和捕捞压力不同的区域环境背景下变化？PIS将在加勒比海三个生物地理区域(巴哈马、伊斯帕尼奥拉和格林纳达/圣文森特/格林纳丁斯)的多个地点进行实验。这些实验将利用模拟自然珊瑚礁栖息地的人工珊瑚礁，以高密度聚集动物。反映生态系统过程的反应变量(例如，海草营养含量、海草生物量、初级生产者多样性)将在珊瑚礁地点测量，并与对照地点(没有珊瑚礁的海草地点)进行比较。生态系统过程可能受到影响的空间范围，即距人工鱼礁的距离，将被量化，并用于检测生态系统反应的生态阈值。预测变量，包括环境营养可获得性、鱼类密度和放牧率的测量，将被用来说明消费者中介的营养供应的相对重要性。分级实验设计和双管齐下的分析将描述生物地理区域之间和内部发现的环境梯度之间的关系，促进所需的概念框架，以预测何时、何地以及为什么消费者中介的营养供应是海草床生态系统过程的重要控制。更广泛的影响：该项目旨在通过广泛整合研究和教育工作，在地区、国家和地方层面最大限度地发挥更广泛的影响。整个项目是与自然保护协会合作设计的，国际和平协会是加勒比咨询委员会的成员。自然保护协会在加勒比海挑战中走在了前列，该挑战旨在到2020年保护20%的海洋栖息地。所有计划中的研究地点都是现有的或拟议的海洋保护区的一部分，作为加勒比挑战倡议的一部分。这项研究的数据将为监测计划、管理战略和保护措施的优先顺序提供信息。在设计地方和国家一级的外联举措时，将考虑到当地的环境和社会机会和挑战。例如，在巴哈马，国际和平协会将帮助在阿巴科岛设计和开发一个新的中心，旨在支持研究、教育和保护活动：Abaco保护、研究和教育中心(Abaco Protection，Research&Education Center)。将扩大“Abaco科学家”外联网站，继续提供一个向公众快速传播信息的平台。重点将是培训在科学方面代表性不足的少数民族学生，在科学、教育和跨文化融合的综合模式下提供经验。

Consumers in marine ecosystems have long been acknowledged for their role in top-down regulation of ecosystems, but their influence through bottom-up pathways such as nutrient supply is often underappreciated and has not been integrated into models of coastal ecosystem dynamics. Yet, nutrient supply from consumers may be a regulating factor when consumers aggregate, such as fishes around structurally complex habitat. Examining this bottom-up mechanistic pathway is essential for a more holistic understanding of seagrass ecosystems, which are important and threatened globally. This study will address the following questions: (1) Does concentrated nutrient supply from consumers result in distinct biogeochemical hot spots in seagrass beds? and (2) How do consumer effects on ecosystem processes vary across regional environmental contexts where nutrient availability and fishing pressure vary? The PIs will conduct experiments at multiple sites within three biogeographic regions in the Caribbean (The Bahamas, Hispaniola, and Grenada/St.Vincent/Grenadines). The experiments will utilize artificial reefs that mimic natural patch reef habitats that concentrate animals at high densities. Response variables reflecting ecosystem processes (e.g., seagrass nutrient content, seagrass biomass, primary producer diversity) will be measured at reef sites and compared with control sites (seagrass sites without reefs). The spatial extent over which ecosystem processes may be affected, i.e., distance from artificial reef, will be quantified and used to detect ecological thresholds in ecosystem responses. Predictor variables, including measures of ambient nutrient availability, fish densities and fish grazing rates, will be used to contextualize the relative importance of consumer-mediated nutrient supply. The hierarchical experimental design and two-pronged analysis will characterize relationships across environmental gradients found among and within the biogeographic regions, facilitating a conceptual framework needed to predict when, where, and why consumer-mediated nutrient supply is an important control of ecosystems processes in seagrass beds. Broader Impacts: The project is designed to maximize broader impacts at regional, national, and local levels through extensive integration of research and education efforts. The entire program is designed in partnership with The Nature Conservancy, for which the PI serves on the Caribbean Advisory Board. The Nature Conservancy is at the forefront of the Caribbean Challenge, an effort to protect 20% of marine habitats by the year 2020. All of the planned study sites are part of current, or proposed, marine protected areas as part of the Caribbean Challenge initiative. Data from the research will inform monitoring plans, management strategies, and prioritization of conservation measures. Outreach initiatives at local and national levels will be designed with sensitivity to local environmental and social opportunities and challenges. For example, in The Bahamas, the PI will help design and develop a new center on Abaco Island intended to support research, education and conservation activities: ACRE (the Abaco Conservation, Research & Education Center). The outreach website "The Abaco Scientist" will be expanded, continuing to provide a platform for quick dissemination of information to the general public. Emphasis will be placed on training minority students under-represented in the sciences, providing experiences within an integrated science, education, and cross-cultural integration model.