The Effects of Elevated Specific Conductivity on the Chronic Toxicity of Mining Influenced Streams Using Ceriodaphnia dubia.

Salinization of freshwater ecosystems as a result of human activities has markedly increased in recent years. Much attention is currently directed at evaluating the effects of increased salinity on freshwater biota. In the Central Appalachian region of the eastern United States, specific conductance from alkaline discharges associated with mountain top mining practices has been implicated in macroinvertebrate community declines in streams receiving coal mining discharges. Whole effluent toxicity testing of receiving stream water was used to test the hypothesis that mine discharges are toxic to laboratory test organisms and further, that toxicity is related to ionic concentrations as indicated by conductivity. Chronic toxicity testing using Ceriodaphnia dubia was conducted by contract laboratories at 72 sites with a total of 129 tests over a 3.5 year period. The database was evaluated to determine the ionic composition of mine effluent dominated streams and whether discharge constituents were related to toxicity in C. dubia. As expected, sulfate was found to be the dominant anion in streams receiving mining discharges with bicarbonate variable and sometimes a substantial component of the dissolved solids. Overall, the temporal variability in conductance was low at each site which would indicate fairly stable water quality conditions. Results of the toxicity tests show no relationship between conductance and survival of C. dubia in the mining influenced streams with the traditional toxicity test endpoints. However, consideration of the entire dataset revealed a significant inverse relationship between conductivity and neonate production. While conductivity explained very little of the high variability in the offspring production (r2 = 0.1304), the average numbers of offspring were consistently less than 20 neonates at the highest conductivities.
Competing Interests: We have the following interests: Mindy Yeager Armstead and Leah Bitzer-Creathers are employed by Potesta & Associates, Inc. Mindy Yeager Armstead, Leah Bitzer-Creathers and Mandee Wilson worked for Alpha Natural Resources and Patriot Mining providing the data in a consulting capacity. Researchers' (Mindy Yeager Armstead and Mandee Wilson) time for conducting the evaluation and preparing the manuscript was supported by the Appalachian Research Initiative for Environmental Sciences (ARIES), an industrial affiliates program at Virginia Tech, which is supported by members that include companies in the energy sector (Norfolk Southern Corporation, Patriot Coal Corporation, TECO Coal Corporation, Natural Resource Partners, Arch Coal and Alpha Natural Resources). There are no patents, products in development or marketed products to declare. This does not alter our adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.