Dissertation Research: Planktonic Coupling in Lakes of Differing Trophic Status: A Multi-Level Experimental Approach

目前在湖泊学方面的大量工作集中在营养供应和食物网结构对浮游生态系统生产力调节的贡献。这一努力促进了社区和生态系统观点的综合。这一提议的主要目的是调查一个从最近的合成中出现的重要问题：不同营养状态的湖泊之间浮游植物-浮游动物耦合的强度是如何变化的？我们建议通过在四个湖泊中进行浮游动物和中生态系统营养物质的实验操作来回答这个问题，这些湖泊包含了广泛的营养状态。浮游动物和营养物的因子操纵将直接评估放牧影响和浮游动物营养物再生对藻类生长的促进程度。将浮游植物暴露于大范围的浮游动物密度将揭示藻类的非线性反应，并评估它们对浮游动物密度可能由季节或年际变化引起的反应。最后，通过在物种、群落和总体（“生态系统”）水平上评估藻类的反应，我们将尝试整合种群、群落和生态系统生态学的特征方法。本研究的结果将有助于理论和应用湖沼学家了解浮游植物和浮游动物之间复杂的相互作用。这种相互作用代表了将光合作用生产转移给食物网中更高层次的消费者的关键环节，并将食物网结构的变化转化为生态系统特性的变化，如初级生产力。

Considerable current effort in limnology focuses on the contributions of nutrient supply and food web structure to the regulation of productivity in planktonic ecosystems. This effort promotes a synthesis of community and ecosystem perspectives. The main goal of this proposal is to investigate an important question that has emerged from such recent syntheses: how does the strength of phytoplankton-zooplankton coupling change between lakes of differing trophic status? We propose to answer this question by performing experimental manipulations of zooplankton and nutrients in mesocosms in four lakes which encompass a broad range of trophic states. Factorial manipulations of zooplankton and nutrients will directly assess grazing impacts and the extent of enhancement of algal growth by zooplankton nutrient regeneration. Exposure of phytoplankton to a broad range of zooplankton densities will reveal non-linear algal responses and evaluate their responses to zooplankton densities that might arise from seasonal or inter-annual variation. Finally, by evaluating algal responses at the species, community, and aggregate ("ecosystem") levels, we will try to integrate approaches characteristic of population, community, and ecosystem ecology. The results of this study will assist both theoretical and applied limnologists in understanding the complex interaction between phytoplankton and zooplankton. This interaction represents the crucial link which transfers photosynthetic production to consumers higher in the food web and which translates changes in food web structure into changes in ecosystem properties such as primary productivity.