Using density, dissimilarity, and taxonomic replacement to characterize mining-influenced benthic macroinvertebrate community alterations in central Appalachia

Elevated specific conductance (SC) in freshwater streams has been associated with alterations of benthic macroinvertebrate communities. Responses by dominant taxa to high salinity in streams can potentially complicate bioassessments. Taxonomic replacement is a method that can detect changes of community identities along an SC gradient as a supplement to conventional metrics that consider taxa richness or abundance. We assessed structural differences among benthic macroinvertebrate communities along an SC gradient in headwater streams influenced by coal mining in the central Appalachian coalfield. Benthic macroinvertebrate communities were sampled quantitatively in 15 southwestern Virginia streams up to six times over the course of a year. Sampled macroinvertebrates were identified to genus when possible and enumerated quantitatively, enabling determination of total-sample density and richness for various taxonomic and functional groups as assemblage structural response metrics. Multivariate methods were used to examine dissimilarities of taxonomic structure among samples along the SC gradient, and Spearman correlations were used to determine associations between SC and group response metrics for each sampling month. Dissimilarity analyses revealed distinct separations of assemblage structure between 1) spring and fall sampling months, and 2) low-SC and high-SC streams. Ephemeroptera richness and density declined with increasing SC, supporting findings by prior studies. Certain tolerant taxa were present at high densities seasonally, masking responses of other taxa within taxonomic and functional groups of which they were members. Leuctra, an SC-tolerant Plecoptera genus, increased in density with increasing SC, and comprised up to 85% of sample densities seasonally in high-SC streams. Richness displayed a strong negative response to SC regardless of season and was a robust indicator of salinity effects. Some functional feeding groups (including collector-gatherers and scrapers) showed seasonal declines in density and/or richness with increasing SC. Taxonomic replacement along an SC gradient was evident in several taxonomic and functional feeding groups during months when richness and density did not exhibit an SC response. Season and SC exerted strong influence over macroinvertebrate community structure in quantitative samples from mining-influenced headwater streams. Taxonomic and functional group composition metrics that do not consider taxonomic identity may not reflect clearly community structure alterations caused by responses of dominant taxa within those groups.
© 2019 Elsevier Ltd