Deciphering planktonic predator-prey interactions: a mechanistic approach

异养原生生物是海洋微生物食物中浮游植物生物量和生产力的重要消耗者。尽管在实验室和野外都付出了相当大的努力，但海洋学家对这些捕食者的觅食生态缺乏机制和预测性的理解。对海洋浮游生物食物网的种群动态和生态学缺乏了解，其根源在于调查尺度的不匹配：驱动浮游生物生长和放牧速度的营养物质和猎物的吸收发生在微观的、个体的水平上，而它们的生态意义和我们的大多数调查发生在更大的尺度上。然而，这些不同尺度的过程是紧密相连的，因为在捕食者、微观运动和行为反应以及最终的宏观捕食者种群分布和环境相关变量的遭遇之间存在因果关系和反馈。使用最近发展的理论和经验方法来克服这种尺度上的不匹配。在这项研究中，研究者将在实验室中量化浮游生物捕食者-猎物的相互作用，并将这些经验观察嵌入到一个理论驱动的模型中，该模型可以预测捕食者的分布和消耗率。捕食者的活动和种群分布将同时被量化，观察尺度从微米和秒到米和小时。如此大范围的覆盖范围提供了将在几个数量级上分离的过程联系起来的机会。因此，宏观过程的微观原因是可以量化的。这些自动视频观察将在大（升）的观察体积中收集，其中猎物的分布是稳定的，并且可以操纵包括梯度和斑块。本文将利用空间结构的猎物分布来检验猎物类型、丰度和分布对异养原生生物在分类学和功能上具有代表性的运动行为和放牧率的重要性。实证结果将嵌入到一个理论驱动的相遇率模型中，该模型预测捕食者种群分布和放牧率。这些模型模拟的目的是确定表征捕食者觅食行为和成功的关键因素。捕食者的放牧率将通过几个独立的方法来量化。对这些冗余但独立的度量进行比较，提供了确定驱动过程的关键因素的机会。实验室和理论工作的紧密结合将改进模型假设，验证模型预测，最重要的是，提供一种参数化复杂生物过程的工具。在这个理论框架下，本研究将对驱动浮游生物分布和种群动态的因素有一个机械的理解。最终，对原生生物觅食行为的机制理解是预测这些浮游植物捕食者的生态作用的关键，从而预测浮游食物网的种群动态。该项目将为研究生和本科生实习生提供培训，通过理论、实证和数学方法的整合来获得定量专业知识。如果有机会，PI将把研究生和本科生的招聘工作重点放在少数民族候选人身上。她在少数族裔服务项目中的持续参与和表现优异的记录将是这一努力的资产。对于海洋学社区来说，这项工作展示了一种破译复杂生物系统过程的新方法。通过将经验数据与完善的理论框架相结合，将建立驱动微观过程与其生态相关的宏观结果之间的机制联系。所提出的工作将提供必要的参数，包括捕食者的行为在海洋生态系统模型。

Heterotrophic protists are important consumers of phytoplankton biomass and productivity in marine microbial food. Despite considerable effort both in the laboratory and the field, oceanographers lack a mechanistic and predictive understanding of the foraging ecology of these predators. This lack of understanding of the population dynamics and ecology of marine planktonic food webs is rooted in a mismatch in investigative scales: uptake of nutrients and prey, that drive plankton growth and grazing rates, occur at the microscopic, individual level, whereas their ecological significance and most of our investigations occur at much larger scales. However, processes at these different scales are tightly linked because there is a causative relationship and feedback between predators, microscopic movements and behavioral responses and the ultimate, macroscopic predator population distribution and encounters of environmentally relevant variables. Using recently developed theoretical and empirical methods that overcome this mismatch in scales.In this study the investigator will quantify planktonic predator-prey interactions in the laboratory and embed these empirical observations in a theoretically-motivated model that predicts predator distributions and consumption rates. Predator movements and population distributions will be simultaneously quantified, ranging in observation scales from micrometers and seconds to meters and hours. Coverage of this vast range of scales provides the opportunity to link processes that are separated over several orders of magnitude. Therefore, the microscopic causes of macroscopic processes can be quantified. These automated video observations will be collected within large (liters) observation volumes in which the distribution of prey is stable and manipulated to include gradients and patches. Spatially structured prey distributions will be used to test the importance of prey type, abundance and distribution on the movement behaviors and grazing rates of a taxonomically and functionally representative set of heterotrophic protists. The empirical results will be embedded in a theoretically-motivated encounter rate model that predicts predator population distributions and grazing rates. These model simulations aim to identify key factors necessary to characterize predator foraging behaviors and success. Predator grazing rates will be quantified through several, independent approaches. Comparison of these redundant but independent measures provides the opportunity to identify key factors driving the process. Tight integration of laboratory and theoretical work will improve model assumptions, validate model predictions and most importantly, provide a tool that parameterizes complex biological processes. With this theoretical framework, this research will develop a mechanistic understanding of the factors driving plankton distributions and population dynamics. Ultimately, a mechanistic understanding of protist foraging behaviors is key to predicting the ecological role of these phytoplankton predators and thus, the population dynamics of planktonic food webs.This project will provide training for a graduate student and undergraduate interns to gain quantitative expertise through the integration of theoretical, empirical and mathematical approaches. Given the opportunity, The PI will focus recruitment efforts of both graduate and undergraduate students on minority candidates. Her continued involvement and demonstrated track record with minority serving programs will be an asset in that endeavor. For the oceanographic community, this work demonstrates a novel approach to deciphering processes in complex biological systems. Through integration of empirical data with a well established theoretical framework, the mechanistic linkages between the driving microscopic processes and their ecologically relevant, macroscopic outcomes will be established. The proposed work will provide the necessary parameters to include predator behaviors in ocean ecosystem models.