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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Bioassessment: Multimetric Development
DEVELOPING TOLERANCE VALUES FOR BENTHIC MACROINVERTEBRATES IN MISSISSIPPI.
D. Bressler1, M.J. Paul1, J.B. Stribling1, and M.B. Hicks2. 1Tetra Tech, Inc., 10045 Red Run Boulevard, Suite 110, Owings Mills, Maryland 21117, 2Mississippi Department of Environmental Quality
Tolerance values are intended to describe the sensitivity of benthic macroinvertebrates to stressors and have been incorporated into various indices as a way to describe overall stream conditions. We developed tolerance values specific to benthic macroinvertebrate taxa found in Mississippi based on the response of individual taxa to stressor gradients. Our dataset consisted of relative abundances of approximately 1000 taxa from 535 samples collected throughout Mississippi except the Alluvial Plain. A suite of stressor gradients representing various combinations of data from 32 physical, chemical, and landscape stressor variables was developed using Principal Components Analysis (PCA). The most important stressor gradient was selected as the one that was most highly correlated with relative taxon abundances. This PCA axis was scaled so that relative taxa abundance values could be directly related to the stressor gradient to determine a taxon-specific tolerance value. Reciprocal averaging was used to select tolerance values based on the point along the PCA axis where the highest relative abundances occurred. Developing tolerance values that are based on non-biological indicators of stress, as done here, is intended to minimize the circularity associated with biologically derived tolerance values.
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