Effects of Anadromous Salmon on North Shore Stream Ecosystems

对于苏必利尔湖北岸的溪流来说，鲑鱼是最近引进的外来物种，可能会改变其历史状态的溪流生态系统。鲑鱼洄游到溪流中，是否为这些溪流生态系统提供了重要的营养物质和高质量有机物？通过实验、比较和稳定的同位素示踪技术，将测试洄游鲑鱼在流经河流生态系统组成部分的营养物和有机物流动中的重要性。据推测，鲑鱼的存在将：1)导致有机物质和无机营养物质从陆地来源转向湖泊来源（鲑鱼尸体和产卵）；2)会改变养分限制的季节模式。这种变化将反映在生态系统的周围植物、细颗粒和溶解有机碳、食草动物、碎纸机和收集器成分的变化中，这些成分可以使用稳定同位素进行追踪。进一步假设，3)一块鲑鱼尸体的大小决定了对生态系统内资源影响的空间尺度。实验和比较研究的结合将提供对养分限制和养分和有机物质通过这些河流生态系统流动的相互依赖的见解。

For streams on the North Shore of Lake Superior, salmon are a recently introduced exotic species, and may be altering the stream ecosystems from their historic state. Are salmon migrations into streams a significant source of nutrients and high quality organic matter for these stream ecosystems? The importance of migration salmon in nutrient and organic matter flow through stream ecosystem components will be tested using experimental, comparative, and stable isotope tracer techniques. It is hypothesized that the presence of salmon will: 1) result in a shift away from terrestrial sources of organic matter and inorganic nutrients toward lake derived sources (salmon carcasses and spawn); and 2) will alter the seasonal patterns of nutrient limitation. This shift will be reflected in changes in periphyton, fine particle and dissolved organic carbon, grazer, shredder, and collector components of the ecosystem which can be traced using stable isotopes. It is further hypothesized that, 3) the size of a patch of salmon carcasses determines the spatial scale of the effect on the resource within the ecosystem. A combination of experimental and comparative studies will provide insight into the interdependence of nutrient limitation and nutrient and organic matter flow through these stream ecosystems.