Collaborative Research: Hypoxia in Marine Ecosystems: Implications for Neritic Copepods

低氧沃茨，通常被称为世界各地沿海生态系统中的"死亡区"，其发生率正在增加。尽管有这些增加，但对低氧沃茨的浮游食物网后果仍然知之甚少。实验室研究表明，缺氧水（2毫克升-1）可导致死亡率，健身和减少产卵的浮游桡足类，在食物网的一个主要环节，支持中上层鱼类。在海洋中的观察表明，缺氧的底部沃茨通常有抑郁症的桡足类丰度相比，含氧量正常的沃茨（2毫克升-1）。氧气浓度相对于深度下降的梯度（氧跃层）可以通过改变桡足类的迁徙行为和深度分布及其与潜在捕食者和猎物的空间一致性，成为沿海中上层生态系统的关键界面。 这个项目将导致对缺氧如何影响桡足类动物的行为和适应性的机械理解。PI将比较自下而上和自上而下的控制桡足类的生态在切萨皮克湾沃茨经历季节性缺氧和那些是常氧。本计画的具体目标是：1）分析桡足类在每小时和每昼夜时间尺度上跨越跃层的迁移行为和细尺度（米）分布的变化，同时检查它们食物的分布和丰富度（浮游植物和微型浮游动物）和捕食者（鱼、胶状浮游动物）; 2）利用一系列测量方法评估低氧对桡足类"适合度"的影响。（体长/体重比、摄食、产卵量和卵孵化成功率），以制定在低氧和常氧沃茨中不同时间和深度捕获的桡足类的状况指数;通过缺氧诱导的桡足类死亡率，不同阶段桡足类在缺氧底层沃茨中的死亡率和上层海水中的变化下控制桡足类的捕食鱼类和胶状浮游动物。Oxyclines可能是一个障碍，垂直迁移的桡足类，从而破坏捕食者回避行为。面对来自鱼类和水母的捕食风险增加，桡足类可能会在一天的部分时间内在缺氧沃茨寻求庇护，和/或在缺氧和常氧沃茨之间进行短期垂直漂移。通过调节垂直迁移，桡足类可能会增加集中在尖跃层的微型浮游动物猎物的利用。低盐度沃茨可能会增加水母对桡足类的消耗，并抑制中上层鱼类的消耗。该项目将评估桡足类在低氧和常氧沃茨中的分布和迁移行为、个体适合度和特定阶段的死亡率。它将研究食物网的后果增加或减少的桡足类和他们的捕食者和猎物的空间一致性在缺氧的底部沃茨的地区，并将有助于从根本上了解富营养化的沿海生态系统的食物网过程。更广泛的影响：随着缺氧变得更加普遍的河口和陆架沃茨，增加了解其对浮游食物网的影响变得至关重要，有效的，基于生态系统的管理。 富营养化和缺氧的影响是JSOST海洋研究优先计划中强调的研究领域。从这个项目中获得的信息将是至关重要的食物网建模渔业生态系统计划的发展切萨皮克湾。从更广泛的意义上说，这项研究是实现切萨皮克湾计划"切萨皮克2000年"协议中的目标所必需的。拟议的研究将支持两名研究生和一名博士后。此外，角点实验室是大西洋中部NSF-COSEE计划的一部分，该项目将支持两名暑期实习教师的参与。Horn Point实验室还参加了NSF本科生研究经验（REU）计划。REU本科生将参与拟议的研究。马里兰州大学环境科学中心的综合和应用网络（www.example.com）的基础设施将促进向公众和环境管理人员传播结果。

The occurrence of low-oxygen waters, often called "dead zones" in coastal ecosystems throughout the world is increasing. Despite these increases, the pelagic food-web consequences of low-oxygen waters remain poorly understood. Laboratory research has demonstrated that hypoxic water ( 2 mg l-1) can result in mortality, reduced fitness and lower egg production of planktonic copepods, a major link in food webs supporting pelagic fish. Observations in the sea indicate that hypoxic bottom waters usually have depressed abundances of copepods compared to normoxic waters ( 2 mg l-1). The gradient of declining oxygen concentration with respect to depth (oxycline) can be a critical interface in coastal pelagic ecosystems by altering the migratory behavior and depth distribution of copepods and their spatial coherence with potential predators and prey. This project will result in a mechanistic understanding of how behavior and fitness of copepods are affected by hypoxia. The PIs will compare bottom-up and top-down controls on the ecology of copepods in Chesapeake Bay waters experiencing seasonal hypoxia and those that are normoxic. Specific objectives of this project are to: 1) analyze changes in migratory behavior and fine-scale (meter) distribution of copepods across the oxycline over hourly and diel time scales while simultaneously examining the distribution and abundance of their food (phytoplankton and microzooplankton) and predators (fish, gelatinous zooplankton); 2) estimate effects of hypoxia on the "fitness" of copepods using a suite of measurements (length/weight ratios, feeding, egg production, and egg hatching success) to develop condition indices of copepods captured at different times and depths in hypoxic and normoxic waters; and 3) evaluate effects of hypoxia on copepod mortality by hypoxia-induced, stage-specific copepod mortality in hypoxic bottom waters and by changes in top-down control of copepods from predation by fish and gelatinous zooplankton.Oxyclines may be a barrier to vertical migration of copepods and thus disruptive to predator avoidance behavior. Faced with increased predation risk from fish and jellyfish, copepods may seek refuge in hypoxic waters for part of the day and/or make short-term vertical excursions between hypoxic and normoxic waters. By regulating vertical migrations, copepods may increase utilization of microzooplankton prey concentrated in the oxycline. Hypoxic waters may elevate consumption of copepods by jellyfish and depress consumption by pelagic fish. This project will evaluate copepod distribution and migration behavior, individual fitness and stage-specific mortality in hypoxic and normoxic waters. It will examine food-web consequences of increased or decreased spatial coherence of copepods and their predators and prey in regions with hypoxic bottom waters and will contribute to fundamental understanding of food-web processes in eutrophic coastal ecosystems.Broader Impacts: As hypoxia becomes more prevalent in estuarine and shelf waters, increased understanding of its effects on planktonic food-webs becomes essential for effective, ecosystem-based management. The effects of eutrophication and hypoxia are areas of research emphasized in the JSOST Ocean Research Priorities Plan. Information gained from this project will be critical for food-web modeling in development of fisheries ecosystem plans for Chesapeake Bay. In a broader sense, the research is needed to achieve goals in the Chesapeake Bay Program's "Chesapeake 2000" Agreement. The proposed research will support two graduate students and a postdoc. In addition, the Horn Point Laboratory is part of the mid-Atlantic NSF-COSEE program and this project will support the participation of two summer teacher interns. The Horn Point Laboratory also participates in the NSF Research Experience for Undergraduates (REU) program. REU undergraduate students will be involved in the proposed research. Dissemination of results to the public and environmental managers will be facilitated by the infrastructure of University of Maryland Center for Environmental Science's Integration and Application Network (www.ian.umces.com).