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Comparing Single species Toxicity Tests to Mesocosm Community-Level Responses to Total Dissolved Solids Comprised of Different Major Ions
Citation:
Lazorchak, Jim, C. Nietch, H. Haring, B. Johnson, P. Weaver, B. Ramakrishan, D. Macke, K. Daniels, S. Decelles, D. Brown, K. Wyatt, AND C. Impellitteri. Comparing Single species Toxicity Tests to Mesocosm Community-Level Responses to Total Dissolved Solids Comprised of Different Major Ions. SETAC Europe 2016, Nantes, FRANCE, May 22 - 26, 2016.
Impact/Purpose:
This is a presentation that will be made to NERL and turned into a poster. It highlights the results of single species toxicity testing done in conjunction with Mesocosm studies at the Experimental Stream Facility over the course of 5 years testing different salt recipes representing different sources of salinity to freshwaters. It also shows that our new mayfly toxicity test method relates well to environmentally relevant species responses,
Description:
Total Dissolved Solids (TDS) dosing studies representing different sources of ions were conducted from 2011-2015. Emergence responses in stream mesocosms were compared to single-species exposures using a whole effluent testing (WET) format and an ex-situ method (single species tests in containers receiving mesocosm water). The first 4 years used a dose-response design for each year’s TDS recipe, which differed based on the relative dominance of major ions. The 2015 experiment tested three of the previous year’s recipes dosed simultaneously but at only one level of moderate specific conductivity (ca. 850 uS/cm). A mayfly, Neocloeon triangulifer, was incorporated for testing alongside the standard WET test organisms. Overall, N. triangulifer tended to be more sensitive than other standard test organisms, but there were differences in sensitivity between the ex-situ method and WET tests. N. triangulifer’s sensitivity in the ex-situ exposure reflected that of mayfly emergence from the mesocosms. Caddisfly emergence was generally as sensitive to TDS exposures as mayflies in 2011-2014 tests, although less sensitive when the excess TDS was dominated by Cl- salts. However, caddisfly emergence was not significantly different from the controls and therefore, not as sensitive as mayfly emergence for the 2015 constant conductivity study. Chironomids were less sensitive to excess TDS than Ephemeroptera and Trichoptera taxa when TDS was dominated by Cl- and NaHCO3, but appeared more sensitive when the TDS was a mixture of SO42- and HCO3-. Mayfly emergence was the only emergence endpoint that demonstrated a clear and consistent adverse response to excess TDS. Emergence in the control was always the highest and sulfate the lowest. Cl- and HCO3- were intermediate and similar in response, but overall significantly lower than the control. In the WET format, mayfly growth in bench tests was: control > Cl- = SO4 > HCO3-. For the 2015 experiment, where Cl-, HCO3-, and SO4 were adjusted to establish a conductivity of approximately 850 uS/cm, the 20% hazardous concentration (HC20) indicated that deleterious effects to mayflies occurred at this conductivity regardless of ion composition. These results suggest that stream benthic communities are significantly more sensitive to excess TDS from coal mining activities that leave leachable spoils rich in carbonate and sulfate than to produced waters emanating from deep oil and gas wells that tend to be dominated by sodium and calcium chloride.
