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This article in JEQ

  1. Vol. 41 No. 1, p. 7-20
    Received: June 16, 2010

    * Corresponding author(s): Patricia.Chambers@ec.gc.ca
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Development of Environmental Thresholds for Nitrogen and Phosphorus in Streams

  1. Patricia A. Chambers *a,
  2. Daryl J. McGoldricka,
  3. Robert B. Bruac,
  4. Chantal Visab,
  5. Joseph M. Culpd and
  6. Glenn A. Benoye
  1. a Environment Canada, Canada Centre for Inland Waters, 867 Lakeshore Blvd., P.O. Box 5050, Burlington, ON L7R 4A6, Canada
    c Environment Canada, National Hydrology Research Centre, 11 Innovation Blvd., Saskatoon, SK S7N 3H5, Canada
    b current address: Parks Canada, 111 Water Street East, Cornwall, ON K6H 6S3, Canada
    d Environment Canada and Canadian Rivers Institute, Dep. Biology, Univ. New Brunswick, 10 Bailey Dr., P.O. Box 4400, Fredericton, NB E3B 5A3, Canada
    e Environment Canada and Agriculture and Agri-Food Canada, Potato Research Centre, 850 Lincoln Rd., P.O. Box 20280, Fredericton, NB E3B 4Z7, Canada. Assigned to Associate Editor Elizabeth Stockdale


Inputs of nutrients (P and N) to freshwaters can cause excessive aquatic plant growth, depletion of oxygen, and deleterious changes in diversity of aquatic fauna. As part of a “National Agri-Environmental Standards Initiative,” the Government of Canada committed to developing environmental thresholds for nutrients to protect ecological condition of agricultural streams. Analysis of data from >200 long-term monitoring stations across Canada and detailed ecological study at ∼70 sites showed that agricultural land cover was associated with increased nutrient concentrations in streams and this, in turn, was associated with increased sestonic and benthic algal abundance, loss of sensitive benthic macroinvertebrate taxa, and an increase in benthic diatom taxa indicative of eutrophication. Chemical thresholds for N and P were defined by applying five approaches, employing either a predetermined percentile to a water chemistry data set or a relationship between water chemistry and land cover, to identify boundaries between minimally disturbed and impaired conditions. Comparison of these chemical thresholds with biological thresholds (derived from stressor–response relationships) produced an approach for rationalizing these two types of thresholds and deriving nutrient criteria. The resulting criteria were 0.01 to 0.03 mg L−1 total P and 0.87–1.2 mg L−1 total N for the Atlantic Maritime, 0.02 mg L−1 total P and 0.21 mg L−1 total N for the Montane Cordillera, ∼0.03 mg L−1 total P and ∼1.1 mg L−1 total N for the Mixedwood Plains, and ∼0.10 mg L−1 total P and 0.39–0.98 mg L−1 total N for the interior prairies of Canada. Adoption of these criteria should result in greater likelihood of good ecological condition with respect to benthic algal abundance, diatom composition, and macroinvertebrate composition.

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