The structuring role of macrophytes in freshwater ecosystems

有些生态系统可以存在于不止一种状态或制度中。发现为什么一些生态系统会保持在一种或另一种状态，以及什么样的扰动会导致制度之间的转变，可能会让我们预测生态系统将如何应对新物种的入侵或气候变化。我研究计划的长期目标是了解湖泊和河流生态系统结构之间的关系以及这些生态系统的功能。我的主要假设是，大型植物是这两个系统的关键结构元素。在河流中，大型植物通过光合作用和呼吸作用影响溶解氧。大型植物为幼鱼提供掩护，但如果代谢足够活跃，也可能产生缺氧区。在浅水草原湖泊中，大型植物通过减少沉积物再悬浮、捕获颗粒、为大型浮游动物提供避难所和释放减少浮游植物生长的化学物质来影响水的清晰度。

Some ecosystems can exist in more than one state or regime. Discovering why some ecosystems remain in one state or another, and what perturbations can cause a shift between regimes, might allow prediction of how ecosystems will respond to invasion by new species or changing climate. The long-term goal of my research program is to understand relations between lake and river ecosystem structure and how those ecosystems function. My major hypothesis is that macrophytes are key structuring elements in both systems. In rivers, macrophytes affect dissolved oxygen through photosynthesis and respiration. Macrophytes provide cover for young fish, yet may also generate hypoxic zones if sufficiently metabolically active. In shallow prairie lakes, macrophytes affect water clarity by reducing sediment resuspension, trapping particles, providing refuge for large-bodied zooplankton and releasing chemicals that reduce phytoplankton growth.