Causes and consequences of hypoxia and pH impacts on zooplankton: Linking movement behavior to vertical distribution.

众所周知，低氧（缺氧）和低pH值对浮游动物（海洋中的微小动物）有深远的生理影响。很可能许多浮游动物个体通过改变垂直迁移行为来减少或避免这些压力。然而，回避反应及其对浮游动物分布的影响，以及浮游动物与捕食者和猎物的相互作用，人们知之甚少。本研究将利用在季节性缺氧河口现场部署的视频系统，提供浮游动物对氧气和pH值的小规模行为反应信息。研究结果将加深我们对浮游动物如何对低氧和pH值条件做出反应的理解，而浮游动物的数量和分布的变化可能会对海洋生态系统和渔业产生深远的影响。该项目将通过发展以海洋技术为基础的公民-科学家活动和浮游生物生态学、海洋变化、生物传感器的建造和使用以及环境数据的定量分析等课程材料，培训研究生，并在服务不足的沿海社区吸引K-12学生和教师。个体定向运动是浮游动物种群分布时空格局的主要机制。大多数浮游动物物种利用运动来选择在生物和非生物变量（如猎物、捕食者、光线、氧气浓度和ph值）不同的水柱位置。物种对脱氧和酸化的特定运动反应可能是通过这种机制，这些应激条件对个体浮游动物的短期、局部影响将被放大或抑制，因为它们向上传播到种群、群落和生态系统水平的动态。本研究将量化关键浮游动物物种对氧气和pH值的反应，使用现场视频系统来测量在季节性缺氧河口缺氧，低pH值与良好氧合，高pH值区域的个体行为变化。浮游动物的分布和运动将通过三种方法进行量化：1)在缺氧地区的剖面系泊上部署一个成像系统，为期两个夏天；2)在拉格朗日漂浮物上部署成像仪，同时在整个水柱上取样；3)垂直分层泵和网拖，验证物种识别和基于视频的丰度估计。这些野外观察将与实验室对浮游动物在氧气和pH梯度下运动的分析相结合，并与空间明确的模型相结合，以预测行为机制如何导致环境压力的大规模影响。

Low oxygen (hypoxia) and low pH are known to have profound physiological effects on zooplankton, the microscopic animals of the sea. It is likely that many individual zooplankton change vertical mirgratio behaviors to reduce or avoid these stresses. However, avoidance responses and their consequences for zooplankton distributions, and for interactions of zooplankton with their predators and prey, are poorly understood. This study will provide information on small-scale behavioral responses of zooplankton to oxygen and pH using video systems deployed in the field in a seasonally hypoxic estuary. The results will deepen our understanding of how zooplankton respond to low oxygen and pH conditions in ways that could profoundly affect marine ecosystems and fisheries through changes in their populations and distributions. This project will train graduate students and will engage K-12 students and teachers in under-served coastal communities by developing ocean technology-based citizen-scientist activities and curricular materials in plankton ecology, ocean change, construction and use of biological sensors, and quantitative analysis of environmental data.Individual directional motility is a primary mechanism underlying spatio-temporal patterns in zooplankton population distributions. Motility is used by most zooplankton species to select among water column positions that differ in biotic and abiotic variables such as prey, predators, light, oxygen concentration, and pH. Species-specific movement responses to de-oxygenation and acidification are likely mechanisms through which short-term, localized impacts of these stressful conditions on individual zooplankton will be magnified or suppressed as they propagate up to population, community, and ecosystem-level dynamics. This study will quantify responses by key zooplankton species to oxygen and pH using in situ video systems to measure changes in individual behavior in hypoxic, low- pH versus well-oxygenated, high-pH regions of a seasonally hypoxic estuary. Distributions and movements of zooplankton will be quantified using three approaches: 1) an imaging system deployed in situ on a profiling mooring over two summers in a hypoxic region, 2) imagers deployed on Lagrangian drifters to sample simultaneously throughout the water column, and 3) vertically-stratified pumps and net tows to verify species identification and video-based abundance estimates. These field observations will be combined with laboratory analysis of zooplankton movements in oxygen and pH gradients, and with spatially-explicit models to predict how behavioral mechanisms lead to large-scale impacts of environmental stresses.