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This article in JEQ

  1. Vol. 33 No. 1, p. 124-132
     
    Received: Feb 8, 2003
    Published: Jan, 2004


    * Corresponding author(s): mcole@savebay.org
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doi:10.2134/jeq2004.1240

Assessment of a δ15N Isotopic Method to Indicate Anthropogenic Eutrophication in Aquatic Ecosystems

  1. Marci L. Cole *a,
  2. Ivan Valielab,
  3. Kevin D. Kroegerc,
  4. Gabrielle L. Tomaskyb,
  5. Just Cebriand,
  6. Cathleen Wigande,
  7. Richard A. McKinneye,
  8. Sara P. Gradyb and
  9. Maria Helena Carvalho da Silvaf
  1. a Save the Bay, 434 Smith St., Providence, RI 02908
    b Boston Univ. Marine Program, Marine Biological Laboratory, Woods Hole, MA 02543
    c Woods Hole Oceanographic Inst., Woods Hole, MA 02543
    d Dauphin Island Sea Lab, P.O. Box 369-370, Dauphin Island, AL 36528
    e USEPA, National Health and Environmental Effects Laboratory, Atlantic Ecology Division, 27 Tarzwell Drive, Narragansett, RI 02882
    f Univ. de São Paulo, Inst. Oceanográfico, Cidade Univ., Butantã SP, Brazil

Abstract

Increased anthropogenic delivery of nutrients to water bodies, both freshwater and estuarine, has caused detrimental changes in habitat, food web structure, and nutrient cycling. Nitrogen-stable isotopes may be suitable indicators of such increased nutrient delivery. In this study, we looked at the differences in response of macrophyte δ15N values to anthropogenic N across different taxonomic groups and geographic regions to test a stable isotopic method for detecting anthropogenic impacts. Macrophyte δ15N values increased with wastewater input and water-column dissolved inorganic nitrogen (DIN) concentration. When macrophytes were divided into macroalgae and plants, they responded similarly to increases in wastewater N, although macroalgae was a more reliable indicator of both wastewater inputs and water-column DIN concentrations. Smooth cordgrass (Spartina alterniflora Loisel.) δ15N increased uniformly with wastewater inputs across a geographic range. We used the relationship derived between S. alterniflora and relative wastewater load to predict wastewater loads in locations lacking quantitative land use data. The predictions matched well with known qualitative information, proving the use of a stable isotopic method for predicting wastewater input.

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