State Water Resources Research Institute Program

Project ID: 2009MT189B
Title: Tracking Human-Derived Nitrogen through Stream Food Webs in a Rapidly Developing Mountain Watershed
Project Type: Research
Start Date: 3/01/2009
End Date: 2/28/2011
Congressional District: At-Large
Focus Categories: Ecology, Nutrients, Wastewater
Keywords: Food webs, Invertebrates, Fishes, Eutrophication, Nutrients, Nitrogen, Stable Isotope Analysis, West Fork of Gallatin River
Principal Investigator: Cross, Wyatt; McGlynn, Brian Leonard (Montana State University)
Federal Funds: $ 16,740
Non-Federal Matching Funds: $ 33,492
Abstract: Nutrient enrichment of stream ecosystems is occurring globally and often has pronounced effects on water quality and ecosystem structure and function. In mountainous regions of the western U.S., the effects of elevated nutrients may be particularly acute because of naturally-low background concentrations, and accelerated population growth and land conversion in predominantly wildland areas. Although many studies have examined nutrient enrichment effects on streams, few have explicitly tracked the origins, fate, and community-level consequences of human-derived nutrients. Here we propose a collaborative study that utilizes stable isotopes of nitrogen (15N and 14N) as a natural tracer of human-derived wastewater to mechanistically link elevated nutrient concentrations to changes in stream community structure. Research will be conducted in the West Fork watershed of the Gallatin River, a site of rapid land use change associated with the Big Sky Ski Resort. This watershed represents an ideal study location given the large amount of previous research on nitrogen dynamics (McGlynn's Laboratory), established differences in stable isotope values of human wastewater and natural sources of nitrogen, and the broad range of stream sites that are physically similar, but vary in magnitude of wastewater input and nitrogen concentrations. Our primary objectives are to (1) quantify spatial and temporal variability of N isotope values in algae, invertebrates and fishes throughout the West Fork watershed to characterize the degree to which human-derived N is utilized by stream food webs; and (2) quantify the community-level consequences of human-derived N by relating spatial variability in stream community structure (invertebrate abundance, biomass, diversity, and trophic structure) to variation in wastewater subsidies. We will accomplish these objectives through seasonal synoptic sampling of algae, invertebrates and fish for isotope analysis, and quantitative sampling of invertebrate community structure. This proposal represents the initiation of a long-term collaboration on food web and ecosystem-level consequences of land use change in the West Fork watershed. Results will be invaluable for developing cost-effective indices of stream 'health' in this region, and as a 'proof-of-concept' for other rapidly developing mountain areas in Montana and beyond.

Progress/Completion Report, 2009, PDF
Progress/Completion Report, 2010, PDF

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