@article{scheibener_conley_buchwalter_2017, title={Sulfate transport kinetics and toxicity are modulated by sodium in aquatic insects}, volume={190}, ISSN={["1879-1514"]}, DOI={10.1016/j.aquatox.2017.06.027}, abstractNote={The salinization of freshwater ecosystems is emerging as a major ecological issue. Several anthropogenic causes of salinization (e.g. surface coal mining, hydro-fracking, road de-icing, irrigation of arid lands, etc.) are associated with biodiversity losses in freshwater ecosystems. Because insects tend to dominate freshwater ecology, it is important that we develop a better understanding of how and why different species respond to salinity matrices dominated by different major ions. This study builds upon previous work demonstrating that major ion toxicity to the mayfly Neocloeon triangulifer was apparently due to the ionic composition of water rather than specific conductance. Synthetic waters with low Ca:Mg ratios and high SO4:Na ratios produced toxicity, whereas waters with higher Ca:Mg ratios and lower SO4:Na ratios were not toxic to mayflies at comparable conductivities. Here we used a radiotracer approach to show that Mg did not competitively exclude Ca uptake at environmentally realistic ratios in 4 aquatic insect species. We characterized SO4 uptake kinetics in 5 mayflies and assessed the influence of different ions on SO4 uptake. Dual label experiments show an inverse relationship between SO4 and Na transport rates as SO4 was held constant and Na was increased, suggesting that Na (and not Cl or HCO3) is antagonistic to SO4 transport. Based on this observation, we tested the hypothesis that increasing Na would protect against SO4 induced toxicity in a Na-dependent manner. Increasing Na from 0.7 to 10.9 mM improved 96-h survivorship associated with 20.8 mM SO4 from 44% to 73% in a concentration dependent manner. However, when Na reached 21.8 mM, survivorship decreased to 16%, suggesting that other interactive effects of major ions caused toxicity under those conditions. Thus, the combination of elevated sulfate and low sodium commonly observed in streams affected by mountaintop coal mining has the potential to cause toxicity in sensitive aquatic insects. Overall, it is important that we develop a better understanding of major ion toxicity to effectively mitigate and protect freshwater biodiversity from salinization.}, journal={AQUATIC TOXICOLOGY}, author={Scheibener, Shane and Conley, Justin M. and Buchwalter, David}, year={2017}, month={Sep}, pages={62–69} }
 @article{conley_watson_xie_buchwalter_2014, title={Dynamic Selenium Assimilation, Distribution, Efflux, and Maternal Transfer in Japanese Medaka Fed a Diet of Se-enriched Mayflies}, volume={48}, ISSN={["1520-5851"]}, DOI={10.1021/es404933t}, abstractNote={Selenium (Se) trafficking in oviparous species remains understudied and a major source of uncertainty in developing sound Se regulations. Here, we utilized (75)Se to follow Se through a simulated natural food chain (water, periphyton, mayflies (Centroptilum triangulifer), fish (Japanese medaka)). We specifically examined Se assimilation efficiency, tissue distribution, efflux rate, and maternal transfer in medaka. Selenium assimilation efficiency (AE) averaged 63.2 ± 8.8% from mayfly diets and was not affected by mayfly [Se] across a dietary range of 5.6-38.7 μg g(-1) (dry wt). However, AE decreased significantly as mayfly larva size increased. Efflux rate constants (ke) were consistent between reproductively inactive (0.066 d(-1)) and spawning females (0.069 d(-1)). Total Se loss rate constant (ke+egg; efflux and egg deposition) was 0.17 d(-1) in spawning females. Interestingly, medaka appeared to rapidly shuttle Se to their eggs directly from their diet via the ovary, as opposed to mobilization from surrounding tissues, resulting in dynamic egg [Se] that was more attributable to recent dietary Se ingestion than female whole body [Se] in this asynchronous spawning fish. Spawning strategy likely plays a large role in the process of fish egg Se deposition and requires further attention to understand risk and toxicity of Se to fish.}, number={5}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Conley, Justin M. and Watson, AtLee T. D. and Xie, Lingtian and Buchwalter, David B.}, year={2014}, month={Mar}, pages={2971–2978} }
 @article{conley_funk_hesterberg_hsu_kan_liu_buchwalter_2013, title={Bioconcentration and Biotransformation of Selenite versus Selenate Exposed Periphyton and Subsequent Toxicity to the Mayfly Centroptilum triangulifer}, volume={47}, ISSN={["0013-936X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84880536702&partnerID=MN8TOARS}, DOI={10.1021/es400643x}, abstractNote={Little is known about the bioaccumulation dynamics, biotransformation processes, or subsequent toxicity to consumers of dissolved selenite (SeO3) versus selenate (SeO4) uptake into aquatic primary producer communities. To address these data gaps, we examined SeO3 and SeO4 bioconcentration into complex freshwater periphyton communities under static and static-renewal conditions. Further, we explored periphyton biotransformation of Se species using X-ray absorption near edge structure (XANES) spectroscopy analysis and changes in the periphyton associated microbial consortium using denaturing gradient gel electrophoresis (DGGE). Last, we fed differentially treated periphyton to the mayfly Centroptilum triangulifer in full life cycle exposures to assess toxicity. Selenite exposed periphyton readily bioconcentrated Se while, in contrast, initial periphyton uptake of SeO4 was negligible, but over time periphyton [Se] increased steadily in conjunction with the formation of dissolved SeO3. XANES analyses revealed that both SeO3 and SeO4 treated periphyton biotransformed Se similarly with speciation dominated by organo-selenide (∼61%). Mayfly survival, secondary production, and time to emergence were similar in both SeO3 and SeO4 treated periphyton exposures with significant adverse effects at 12.8 μg g(-1) ((d.w.) secondary production) and 36 μg g(-1) ((d.w.) survival and development time). Overall, dissolved selenium speciation, residence time, and organisms at the base of aquatic food webs appear to be the principal determinants of Se bioaccumulation and toxicity.}, number={14}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Conley, Justin M. and Funk, David H. and Hesterberg, Dean H. and Hsu, Liang-Ching and Kan, Jinjun and Liu, Yu-Ting and Buchwalter, David B.}, year={2013}, month={Jul}, pages={7965–7973} }
 @article{kunz_conley_buchwalter_norberg-king_kemble_wang_ingersoll_2013, title={USE OF RECONSTITUTED WATERS TO EVALUATE EFFECTS OF ELEVATED MAJOR IONS ASSOCIATED WITH MOUNTAINTOP COAL MINING ON FRESHWATER INVERTEBRATES}, volume={32}, ISSN={["1552-8618"]}, DOI={10.1002/etc.2391}, abstractNote={Abstract}, number={12}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Kunz, James L. and Conley, Justin M. and Buchwalter, David B. and Norberg-King, Teresa J. and Kemble, Nile E. and Wang, Ning and Ingersoll, Christopher G.}, year={2013}, month={Dec}, pages={2826–2835} }
 @article{conley_funk_cariello_buchwalter_2011, title={Food rationing affects dietary selenium bioaccumulation and life cycle performance in the mayfly Centroptilum triangulifer}, volume={20}, ISSN={["1573-3017"]}, DOI={10.1007/s10646-011-0722-1}, abstractNote={Selenium effects in nature are mediated by the relatively large bioconcentration of aqueous Se by primary producers and smaller, yet critical, dietary transfers to primary consumers. These basal processes are then propagated through food webs to higher trophic levels. Here we quantified the movement of dissolved Se (as selenite) to periphyton, and used the resultant periphyton as a food source for conducting full life-cycle dietary Se exposures to the mayfly Centroptilum triangulifer. Periphyton bioconcentrated Se ~2,200-fold from solution in a log-linear fashion over dissolved Se concentrations ranging from 1.1 to 23.1 μg L(-1). We examined the influence of two feeding ration levels (1x and 2x) on trophic transfer, tissue Se concentrations, maternal transfer, and functional endpoints of mayfly performance. Mayflies fed a lesser ration (1x) displayed greater trophic transfer factors (mean TTF, 2.8 ± 0.4) than mayflies fed 2x rations (mean TTF, 1.1 ± 0.3). In 1x exposures, mayflies exhibited significant (p < 0.05) reductions in survivorship and total body mass at dietary [Se] ≥ 11.9 μg g(-1), reduced total fecundity at ≥ 4.2 μg g(-1), and delayed development at ≥ 27.2 μg g(-1). Mayflies fed a greater ration (2x) displayed reduced tissue Se concentrations (apparently via growth dilution) relative to 1x mayflies, with no significant effects on performance. These results suggest that the influence of Se on mayfly performance in nature may be tied to food resource availability and quality. Furthermore, nutritional status is an important consideration when applying laboratory derived estimates of toxicity to risk assessments for wild populations.}, number={8}, journal={ECOTOXICOLOGY}, author={Conley, J. M. and Funk, D. H. and Cariello, N. J. and Buchwalter, D. B.}, year={2011}, month={Nov}, pages={1840–1851} }