Interactions Between Planktonic Community Structure and Nutrient Cycling Processes in Freshwater Ecosystems

本项目将继续研究水生生态系统中浮游生物群落结构与养分循环之间的主要相互作用。由于群落组成与营养动态在许多复杂的因果关系中紧密相连，因此很难评估任何特定生境中不同相互作用的相对重要性。例如，磷肥、水柱氮磷和浮游鱼类丰度都可能（直接或间接）独立地影响浮游植物和浮游动物的丰度和物种组成。后一种变量可能反过来影响养分循环速率和途径（直接通过水柱效应，或间接通过沉降和底栖生物再生）。三个主要变量可以通过实验操作来确定在何种情况下特定过程是重要的：浮游动物食性鱼类的丰度，浮游植物可吸收的氮磷比，以及添加到环境中的磷的绝对数量。使用一组16个大型实验池，研究人员将一次操作两个变量，每个处理4个重复池。目前，N:P（高vs低）和fish（存在vs不存在）正在被操纵。这个增量将是一个进一步的1年实验，以操纵第三个变量，P-负载（高vs低）+鱼。研究将有助于建立基本的生态概念，并将为湖泊管理提供有用的数据。

This project will continue an investigation on the major interactions between planktonic community structure and nutrient cycling in aquatic ecosystems. Because community composition is tightly coupled with nutrient dynamics in a number of complex cause-effect relationships, the relative importance of different interactions in any particular habitat can be difficult to assess. For example, phosphorus fertilization, water column N:P and planktivorous fish abundance may each independently influence (directly or indirectly) phytoplankton and zooplankton abundance and species composition. The latter variables may, in turn, influence nutrient cycling rates and routes (either directly through water-column effects, or indirectly through sedimentation and benthic regeneration). Three major variables can be experimentally manipulated to identify circumstances under which particular processes are important: the abundance of zooplanktivorous fish, the ratio of nitrogen to phosphorus available for uptake by phytoplankton, and the absolute amount of phosphorus added to the environment. Using a set of 16 large experimental ponds, researchers will manipulate two variables at a time with 4 replicate ponds per treatment. At present, N:P (high vs low) and fish (presence vs. absence) are being manipulated. This increment will be a further 1-year experiment to manipulate the third variable, P- loading (high vs. low) again + fish. Research will contribute to basic ecological concepts and will provide data useful in lake management.