Wetland Flowpaths Mediate Nitrogen and Phosphorus Concentrations across the Upper Mississippi River Basin.
Samson G Mengistu, Heather E Golden, Charles R Lane, Jay C Christensen, Michael L Wine, Ellen D'Amico, Amy Prues, Scott G Leibowitz, Jana E Compton, Marc H Weber, Ryan A Hill
Author Information
Samson G Mengistu: National Research Council, National Academy of Science @ US Environmental Protection Agency (USEPA), Office of Research and Development, Cincinnati, Ohio USA.
Heather E Golden: USEPA, Office of Research and Development, National Center for Measurement and Modeling, Cincinnati, Ohio, USA.
Charles R Lane: USEPA, Office of Research and Development, National Center for Measurement and Modeling, Cincinnati, Ohio, USA.
Jay C Christensen: USEPA, Office of Research and Development, National Center for Measurement and Modeling, Cincinnati, Ohio, USA.
Michael L Wine: Oak Ridge Institute for Science and Education @ US Environmental Protection Agency (USEPA), Office of Research and Development, Cincinnati, Ohio USA.
Ellen D'Amico: Pegasus Technical Services, Inc., Cincinnati, Ohio, USA.
Amy Prues: Pegasus Technical Services, Inc., Cincinnati, Ohio, USA.
Scott G Leibowitz: USEPA, Office of Research and Development, National Center for Public Health and Environmental Assessment, Corvallis, Oregon, USA.
Jana E Compton: USEPA, Office of Research and Development, National Center for Public Health and Environmental Assessment, Corvallis, Oregon, USA.
Marc H Weber: USEPA, Office of Research and Development, National Center for Public Health and Environmental Assessment, Corvallis, Oregon, USA.
Ryan A Hill: USEPA, Office of Research and Development, National Center for Public Health and Environmental Assessment, Corvallis, Oregon, USA.
Eutrophication, harmful algal blooms, and human health impacts are critical environmental challenges resulting from excess nitrogen and phosphorus in surface waters. Yet we have limited information regarding how wetland characteristics mediate water quality across watershed scales. We developed a large, novel set of spatial variables characterizing hydrological flowpaths from wetlands to streams, that is, "wetland hydrological transport variables," to explore how wetlands statistically explain the variability in total nitrogen (TN) and total phosphorus (TP) concentrations across the Upper Mississippi River Basin (UMRB) in the United States. We found that wetland flowpath variables improved landscape-to-aquatic nutrient multilinear regression models (from = 0.89 to 0.91 for TN; = 0.53 to 0.84 for TP) and provided insights into potential processes governing how wetlands influence watershed-scale TN and TP concentrations. Specifically, flowpath variables describing flow-attenuating environments, for example, subsurface transport compared to overland flowpaths, were related to lower TN and TP concentrations. Frequent hydrological connections from wetlands to streams were also linked to low TP concentrations, which likely suggests a nutrient source limitation in some areas of the UMRB. Consideration of wetland flowpaths could inform management and conservation activities designed to reduce nutrient export to downstream waters.
