Benthic Insect Community Structure in Cumberland Mountain Streams Twenty-five Years After Coal Strip Mining

In order to evaluate long-term impacts of coal strip mining on small stream benthic fauna in the Cumberland Mountains of east Tennessee, four streams, two in watersheds mined twenty-five years ago and two undisturbed, were sampled monthly for six months, January through June, 1979. Benthos was sampled by collecting eight Surber samples, each two ft.² in area, from similar riffles in each stream. At the collection sites pH, dissolved o₂, and velocity were measured. Water samples were analyzed in the laboratory for alkalinity and hardness (measured as mg/1 CaCO₃) and dissolved Fe and SO₄ (mg/1) concentrations.

Benthic data analysis was both quantitative and qualitative. Quantitative evaluation included analysis of variance of density of individuals/unit area, numbers of taxa, and species diversity (Shannon-Weaver index). Qualitative analysis included evaluation of the distribution and abundance of various taxa among the streams and the taxonomic similarity (computed by the modified Sorenson similarity coefficient).

Results indicated that the undisturbed streams had significantly greater densities of individuals and numbers of taxa, but not species diversity. Qualitatively, the undisturbed steams have more taxa with many individuals than do the streams affected by strip mining. The similarity index indicated the undisturbed streams to be most similar with the mining-affected streams being the next most similar. Although this study does not prove that strip mining caused the observed decreases in numbers of taxa and density of individuals per unit area, it suggests that such extensive damage to small watersheds may reduce benthic productivity for as long as twenty-five years, and indicates further research may be necessary to determine factors causing a depressed fauna for so long.