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Factors affecting ammonium uptake in streams – an inter-biome perspective |
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| Authors: | Jackson R Webster Patrick J Mulholland Jennifer L Tank H Maurice Valett Walter K Dodds Bruce J Peterson William B Bowden Clifford N Dahm Stuart Findlay Stanley V Gregory Nancy B Grimm Stephen K Hamilton Sherri L Johnson Eugènia Martí William H Mcdowell Judy L Meyer Donna D Morrall Steven A Thomas Wilfred M Wollheim |
| Institution: | Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, VA, U.S.A.;Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, U.S.A.;Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, U.S.A.;Division of Biology, Kansas State University, Manhattan, KS, U.S.A.;Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA, U.S.A.;School of Natural Resources, University of Vermont, Burlington, VT, U.S.A.;Department of Biology, University of New Mexico, Albuquerque, NM, U.S.A.;Institute of Ecosystem Studies, Millbrook, NY, U.S.A.;Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR, U.S.A.;Department of Biology, Arizona State University, Tempe, AZ, U.S.A.;Kellogg Biological Station, Michigan State University, E Gull Lake Dr., Hickory Corners, MI, U.S.A.;USDA Forest Service, PNW Research Station, Corvallis, OR, U.S.A.;Centre d'Estudis Avancats de Blanes (CSIC), Blanes, Girona, Spain;Department of Natural Resources, University of New Hampshire, Durham, NH, U.S.A.;Institute of Ecology, University of Georgia, Athens, GA, U.S.A.;Environmental Science Department, Procter and Gambell Company, Cincinnati, OH, U.S.A.;Eco-Metrics, Inc., Pendleton, OR, U.S.A.;Complex Systems Research Center, University of New Hampshire, Durham, NH, U.S.A. |
| Abstract: | 1. The Lotic Intersite Nitrogen eXperiment (LINX) was a coordinated study of the relationships between North American biomes and factors governing ammonium uptake in streams. Our objective was to relate inter‐biome variability of ammonium uptake to physical, chemical and biological processes. 2. Data were collected from 11 streams ranging from arctic to tropical and from desert to rainforest. Measurements at each site included physical, hydraulic and chemical characteristics, biological parameters, whole‐stream metabolism and ammonium uptake. Ammonium uptake was measured by injection of 15N‐ammonium and downstream measurements of 15N‐ammonium concentration. 3. We found no general, statistically significant relationships that explained the variability in ammonium uptake among sites. However, this approach does not account for the multiple mechanisms of ammonium uptake in streams. When we estimated biological demand for inorganic nitrogen based on our measurements of in‐stream metabolism, we found good correspondence between calculated nitrogen demand and measured assimilative nitrogen uptake. 4. Nitrogen uptake varied little among sites, reflecting metabolic compensation in streams in a variety of distinctly different biomes (autotrophic production is high where allochthonous inputs are relatively low and vice versa). 5. Both autotrophic and heterotrophic metabolism require nitrogen and these biotic processes dominate inorganic nitrogen retention in streams. Factors that affect the relative balance of autotrophic and heterotrophic metabolism indirectly control inorganic nitrogen uptake. |
| Keywords: | biome metabolism nitrogen stable isotope transient storage |