by Arthur D. Bradfield
This report is available as a pdf below
Benthic invertebrate and water-quality data collected during previous U.S. Geological Survey studies to provide background hydrologic information on streams draining Tennessee coal reserves were evaluated to identify possible relations between stream biota and water quality. Linear regressions produced low correlation coefficients relating the number of taxa per sample, total number of organisms per sample, sample diversity, and percentage composition of selected orders of invertebrates with average water-quality parameter values available at sampling stations (r < 0.62 at p = 0.05). Analyses of these data by linear regressions explained little of the variability in benthic invertebrate samples primarily because the distributions of benthic organisms along environmental gradients are nonlinear. Variability in substrate characteristics in the study area and seasonal insect emergence patterns also complicated interpretation of these data. However, analysis of variance tests did indicate significant trends towards reduced number of taxa, number of organisms, and sample diversity at stations with relatively poor water-quality conditions. Decreasing percentage composition of Ephemeroptera was generally accompanied by an increase in percent Diptera at stations with higher water-quality constituent concentrations and acidic pH (< 6.0 units). These trends indicate significant differences in benthic communities at sites with evidence of more severe land-use impacts. Additional data on benthic invertebrates, water quality, and physical habitat conditions, along with analyses of data using multivariate statistical methods are needed to define ecological relations between specific groups of invertebrates and environmental conditions.
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