Benthic macroinvertebrate community structure responses to multiple stressors in mining-influenced streams of central Appalachia USA

Headwaters are crucial linkages between upland ecosystems and navigable waterways, serving as important sources of water, sediment, energy, nutrients and invertebrate prey for downstream ecosystems. Surface coal mining in central Appalachia impacts headwaters by burying streams and introducing pollutants to remaining streams including excessive sediments, trace elements, and salinity. Benthic macroinvertebrates are widely used as indicators of biological conditions of streams and are frequently sampled using semi-quantitative methods that preclude calculations of areal densities. Studies of central Appalachian mining impacts in non-acidic streams often focus on biotic effects of salinity, but other types of pollution and habitat alteration can potentially affect benthic macroinvertebrate community (BMC) structure and perhaps related functions of headwater streams. Objectives were: 1) use quantitative sampling and enumeration to determine how density, richness, and composition of BMCs in non-acidic central Appalachian headwaters respond to elevated salinity caused by coal surface mining, and 2) determine if BMC structural differences among study streams may be attributed to habitat and water-quality effects in addition to elevated salinity. I analyzed BMC structure, specific conductance (SC, surrogate measure of salinity), and habitat-feature data collected from 15 streams, each visited multiple times during 2013-2014. BMC structure changed across seasonal samples. Total benthic macroinvertebrate densities did not appear to be impacted by SC during any months, but reduced densities of SC-sensitive taxa were offset by increased densities of SC-tolerant taxa in high-SC streams. Total richness also declined with increasing SC, whereas BMCs in high-SC streams were simplified and dominated by a few SC-tolerant taxa. Taxonomic replacement was detected in high-SC streams for groups of benthic macroinvertebrates that did not exhibit density or richness response, showing that taxonomic replacement could be a valuable tool for detecting BMC changes that are not evident from analyses using conventional metrics. Specific conductance, water-column selenium concentration, large-cobble-to-fines ratio of stream substrate, and relative bed stability were associated with changes in BMC structure. These results suggest multiple stressors are influencing BMCs in mining-influenced Appalachian streams. These findings can inform future management of headwater streams influenced by mining in central Appalachia.