Forays and Foraging by Marine Zooplankton

知识价值：生物海洋学的一个主要挑战是了解和预测浮游动物的垂直分布和觅食行为。这些生物作为微粒的消费者和生产者，在远洋生态系统中发挥着核心作用，并且作为鱼类等高营养类型的猎物，是远洋食物网的关键环节。对浮游动物在这些过程中的作用的预测性理解取决于对它们的深度选择和觅食行为的了解。例如，浮游动物在水柱中的觅食位置不仅会深刻影响其摄食速度和生长速度，而且还会影响其产生与摄食有关的颗粒的位置。此外，在垂直结构的平流场中，个体的扩散取决于它们在水柱中的位置，而这可能由其他性质决定。虽然浮游动物的垂直迁移是深度选择和觅食行为最显著的表现形式，但有大量证据表明，浮游动物在比昼夜周期更短的时间尺度上进行了大量的垂直迁移。这种行为的生物学意义目前尚不清楚，但如果频繁和广泛，将其纳入浮游动物种群动态和扩散模型将是必不可少的。这项研究的目的是在海洋中验证这样一种假设，即当浮游桡足类动物在靠近表层的水域活动时，它们会反复地垂直移动（突袭）进出食物丰富的层。研究者将通过直接拦截（诱捕）垂直迁移的成年个体和三种浮游桡足类动物的最后前成年阶段（桡足类第五阶段）来验证这一假设。桡足类动物将在足够短的时间尺度内取样，以检测它们的重复攻击，并评估它们的攻击是否以觅食为目的。研究小组将测量少量的生理状态和条件的关键指标，以评估这种觅食行为对个体桡足类的生理影响。观测将在不同季节、不同取食条件、水柱物理结构（热分层强度）和夜间时段进行。最后，他们将把观察结果整合到一个以个体为基础的桡足动物捕食和觅食模型中。研究结果对确定浮游动物垂直分布和觅食行为的过程及其潜在意义具有重要意义。这些考虑不仅是理解和模拟海洋浮游动物种群动态的基础，也是预测浮游动物对环境变化（如与全球气候变化相关的环境变化）的可能响应的基础，也是理解物质、营养物质和能量从表层水到海洋深处的垂直通量的基础。更广泛的影响：该项目将涉及两名研究生研究助理的直接参与，他们将从事相关的研究项目。该研究还将与美国国家海洋和大气管理局位于加利福尼亚州太平洋格罗夫的太平洋渔业环境实验室建立伙伴关系。与该伙伴关系相关，在拟议的研究中获得的见解也应该对渔业管理有价值，因为它可以促进对环境变化如何影响许多受管理的海洋生物资源（如幼年鲑鱼和其他小型远洋鱼类）的主要猎物种类的分布和可用性的理解。

Intellectual Merit: A major challenge for biological oceanography is to understand and predict the vertical distribution and foraging behavior of planktonic animals. These organisms play central roles in pelagic ecosystems as consumers and producers of particles and as crucial links in pelagic food webs as prey for higher trophic types such as fish. A predictive understanding of the roles of zooplankton in these processes hinges on knowledge of their depth selection and foraging behavior. For example, where a planktonic animal forages in the water column can profoundly affect not only its feeding rate and growth rate, but also where it produces particles associated with its feeding. Moreover, in vertically structured advective fields, the dispersal of individuals depends on their position in the water column that may be dictated by other properties. Although diel vertical migration is the most conspicuous expression of depth selection and foraging behavior in zooplankton, there is much evidence indicating that zooplankton make excursions of substantial vertical extent on time scales shorter than the diel period. The biological significance of such behavior is currently unknown, but if frequent and widespread, its inclusion in models of zooplankton population dynamics and dispersal will be essential. The goal of this research is to test, in the ocean, the hypothesis that when occupying near surface waters planktonic copepods make repeated vertical excursions (forays) into and out of the food-rich layer. The Investigators will test the hypothesis by directly intercepting (trapping) vertically migrating individual adults and the last pre-adult stage (copepodid stage 5) of three species of planktonic copepods. Copepods will be sampled on sufficiently short time scales to detect repeated forays and to assess whether the forays are for the purpose of feeding. The research team will measure a small number of key indicators of physiological state and condition to assess the physiological consequences for individual copepods of such foraging behavior. The observations will be obtained in different seasons with different feeding conditions, water column physical structure (intensity of thermal stratification) and nocturnal period. Finally, they will integrate the observations in an individual-based model of copepod forays and foraging. The results of the research will be important for identifying and assessing processes and their potential significance in determining the vertical distribution and foraging behavior of zooplankton. These considerations are fundamental not only to understanding and modeling the population dynamics of marine zooplankton, but also to predicting the possible response of zooplankton to environmental changes, such as those associated with global climate change, and to understanding the vertical flux of materials, nutrients, and energy from surface waters to depth in the ocean.Broader impacts: The project will involve direct participation of two graduate student research assistants, who will pursue related research projects. The research will also develop a partnership with NOAA's Pacific Fisheries Environmental Laboratory in Pacific Grove, CA. Relevant to that partnership, the insights gained in the proposed research should also be valuable to fisheries management in terms of advancing understanding of how environmental change may affect the distribution and availability of a major class of prey items for many managed living marine resources, such as juvenile salmon and other small pelagic fish.