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SFS Annual Meeting

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WETLAND INFLUENCES ON A CONTAMINATED RIVER: DYNAMICS OF BIOGEOCHEMICAL PROCESSING DOMAINS

Discrete components of aquatic ecosystems can be thought of as nutrient processing domains (PDs) that, depending on net biogeochemical and hydrologic properties, may act as either nutrient donors, conveyors, transformers, or removers. Interaction of various processing domains within a lotic continuum ultimately determines loads to receiving waters by dictating net nutrient export form and abundance. This approach was applied to a tributary stream to assess its influence on nutrient budgets of a larger river as reflected in spatiotemporal patterns of nutrient loading rates. We analyzed dissolved nutrient concentrations in a river along a longitudinal gradient, sampling each river-km and tributary confluence to identify zones of net nutrient input. In autumn, a donor tributary increased background river N concentration from 0.003 to 0.042 µg NO3-N L-1. The following spring, N concentrations above and below the tributary confluence showed a similar pattern, with ammonium as the primary N-form, increasing from 0.023 to 0.099 µg NH4-N L-1. We hypothesize this nitrogen subsidy is derived from a large wetland complex that dominates the contributing tributary, acting as a seasonally-driven biological hotspot of N production with spatiotemporal variability accounting for discrete nutrient processing domains.

Marc Peipoch (Co-Presenter/Co-Author), Stroud Water Research Center, mpeipoch@stroudcenter.org;


H. Maurice Valett (Co-Presenter/Co-Author), University of Montana, maury.valett@umontana.edu;


Patrick Hurley (Primary Presenter/Author), University of Montana, patrick1.hurley@umontana.edu;