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Presented at the NABS Annual meeting, Anchorage, Alaska, 2006
in Tribal Bioassessment Programs And Biocriteria Development 2
Characterizing a stressor gradient for state and tribal water quality programs
J.L. Lessard1, J.D. Allan2, J.J.H. Ciborowski3, and L.B. Johnson4.1Tetra Tech Inc., Owings Mills, MD 21117, 2School of Natural Resources & Environment, University of Michigan, Ann Arbor, MI 48109, 3Deptartment of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada, 4Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN 55811
The Biological Condition Gradient (BCG) is a narrative model for interpreting biological responses to increasing stressors on aquatic ecosystems. Integral to the BCG development is characterizing the model’s x-axis—the stressor gradient (SG). Stressors are biological, physical or chemical factors that adversely affect aquatic organisms. The sources of these stressors are often related to human activities at the landscape scale (e.g., urbanization, agricultural, or mining practices). Multiple stressors often result in cumulative effects that complicate characterizing a stressor gradient. Scientists have attempted to quantify and partition the influence of multiple stressors on aquatic ecosystems. Examples of recent methods being tested are: the landscape development index which uses emergy as a currency for disturbance; the human disturbance gradient which places multiple stressors and their sources into narrative tiers; and the Great Lakes Environmental Indicators Reference Condition model which uses a fuzzy–set type approach to identify thresholds of stressor influence. These three approaches serve as the foundation for developing a workable BCG model for water quality agencies to characterize the multiple and cumulative stressors affecting the condition of aquatic resources. This model also provides a consistent and standard approach applicable across the entire US, from which collaborative efforts will benefit.
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