Pacific salmon are an important nutrient subsidy in streams in their native range throughout the northern Pacific Rim, and recent introductions have expanded their influence to other regions such as the Great Lakes. During annual salmon migrations and spawning, salmon-derived nutrients (SDN) enter streams and influence both organisms and ecosystem function. For example, stream algae and macroinvertebrates increase during salmon runs and decaying salmon carcasses provide for longer-term SDN storage in streams. Previous research has shown that the effect of SDN in streams is not always consistent, but dependent on stream structure and regional climate patterns. In this study, a suite of ecosystem-scale metrics will be measured on streams in the Great Lakes region to complement a similar dataset from Southeast Alaska. These two regions have differing stream structure and climate, and the comparison will provide an understanding of the underlying controls that determine ecosystem response to SDN subsidies. As a result of human actions, some streams have diminished salmon runs, particularly from dams or over-fishing, while others receive increasingly larger runs as a result of hatchery stocking. Therefore, a thorough understanding of how stream structure and climatic conditions determine the influence of SDN subsidies is necessary for effective management of current salmon runs in both native and introduced ranges.
The comparative inter-biome approach will allow managers to assess and predict the response of SDN subsidies on a range of stream ecosystems, enhancing the potential success of stream restoration and salmon conservation projects. Results will be disseminated to appropriate Federal agencies and non-governmental organizations such as The Nature Conservancy.
