Levels of Dissolved Solids Associated with Aquatic Life Effects in Headwater Streams of Virginia Central Appalachian Coalfield Region

Benthic macroinvertebrate communities in headwater streams influenced by Appalachian coal mining often differ from communities in minimally disturbed streams. Elevated levels of total dissolved solids (TDS) associated with mining have been suggested as stressors to these communities. In studies of such streams conducted to date, both non-TDS stressors and elevated TDS have been present as potential influences on biota. In the study reported here the association between dissolved salts and benthic macroinvertebrate community structure was examined using a familylevel multimetric index and genus-level taxa sensitivity distributions. Test sites were selected along a gradient of elevated TDS, with non-TDS factors of reference quality. Virginia Stream Condition Index (VASCI) scores were regressed against log-transformed measures of TDS, specific conductance, and sulfate (SO4 2-) using ordinary least squares and quantile regression techniques. Biological effects, as defined by VASCI scores <60 indicating stressed or severely stressed conditions, were observed with increasing probability from 0% at ≤ 190 mg/L TDS to 100% at ≥ 1,108 mg/L TDS, with 50% probability of effects observed at 422 mg/L TDS. Associations between water quality measures and biological condition were variable, with approximately 48% of the variance explained by TDS. Genus-level analysis using a field sensitivity distribution approach indicated 95% of reference genera were observed at sites with TDS ≤ 281 mg/L, and 80% of genera were observed at sites with TDS ≤ 411 mg/L. This is evidence that TDS, specific conductance, or SO4 2-can be used to establish dissolved solids levels for streams influenced by Appalachian coal mining above which aquatic life effects are increasingly probable.