@article{cochran_funk_buchwalter_2023, title={Physiological and life history responses in a mayfly (Callibaetis floridanus) inhabiting ponds with saltwater intrusion}, volume={11}, ISSN={["2296-701X"]}, DOI={10.3389/fevo.2023.1135924}, abstractNote={Freshwater salinity varies in natural systems and plays a role in species distribution. Anthropogenic alterations to freshwater salinity regimes include sea level rise and subsequent intrusion of saline waters to inland habitats. While mayflies are generalized to be sensitive to increasing salinity, we still know remarkably little about the physiological processes (and their plasticity) that determine the performance of species in a changing world. Here, we explored life-history outcomes and physiological plasticity in a population of Callibaetis floridanus (Ephemeroptera: Baetidae) from a coastal pond that routinely experiences saltwater intrusion. We reared naiads from egg hatch to adulthood across a gradient of increasing salinities (113, 5,020, 9,921 μS/cm). Radiotracer flux studies (22Na, 35SO4, and 45Ca) were conducted in naiads reared at each salinity, revealing a positive association between ionic concentration and uptake rates. However, the influence of rearing history on ionic influx rates was apparent when naiads were transferred from their respective rearing water to the other experimental conditions. For example, we observed that naiads reared in the low salinity treatment (113 μS/cm) had 10.8-fold higher Na uptake rates than naiads reared at 9,921 μS/cm and transferred to 113 μS/cm. Additionally, naiads acclimated to the higher salinity water exhibited reduced uptake in ion-rich water relative to those reared in more dilute conditions (e.g., in 9,921 μS/cm water, 113 and 5,020 μS/cm acclimated naiads had 1.5- and 1.1-fold higher Na uptake rates than 9,921 μS/cm acclimated naiads, respectively). We found no significant changes in survival (80 ± 4.4%, mean ± s.e.m.) or naiad development time (24 ± 0.3 days, mean ± s.e.m.) across these treatments but did observe a 27% decrease in subimago female body weight in the most dilute condition. This reduction in female weight was associated with higher oxygen consumption rates in naiads relative to the other rearing conditions. Collectively, these data suggests that saline adapted C. floridanus may be more energetically challenged in dilute conditions, which differs from previous observations in other mayfly species.}, journal={FRONTIERS IN ECOLOGY AND EVOLUTION}, author={Cochran, Jamie K. and Funk, David H. and Buchwalter, David B.}, year={2023}, month={Mar} }
 @article{cochran_banks_buchwalter_2023, title={Respirometry reveals major lineage-based differences in the energetics of osmoregulation in aquatic invertebrates}, volume={226}, ISSN={["1477-9145"]}, DOI={10.1242/jeb.246376}, abstractNote={ABSTRACT}, number={20}, journal={JOURNAL OF EXPERIMENTAL BIOLOGY}, author={Cochran, Jamie K. and Banks, Catelyn and Buchwalter, David B.}, year={2023}, month={Oct} }
 @article{orr_collins_jima_buchwalter_2023, title={Salinity-induced ionoregulatory changes in the gill proteome of the mayfly, Neocloeon triangulifer}, volume={316}, ISSN={["1873-6424"]}, url={https://doi.org/10.1016/j.envpol.2022.120609}, DOI={10.1016/j.envpol.2022.120609}, abstractNote={Ecologists have observed declines in the biodiversity of sensitive freshwater organisms in response to increasing concentrations of major ions (salinization). Yet, how changing salinities physiologically challenge aquatic organisms, such as mayflies, remains remarkably understudied. Moreover, it is not well understood the degree to which species respond and acclimate to salinity changes. Our lab is developing the Baetid mayfly, N. triangulifer, as a model organism for physiological research. We have previously described acclimatory changes in both ion flux rates and altered mRNA transcript levels in response to chronic exposures to elevated major ion concentrations at the whole animal level. In the present study, we use shotgun proteomics to identify the specific proteins associated with apical ion transport and how their abundance changes in response to chronic salinity exposures in gills. Gills were isolated from the penultimate nymphal stage of N. triangulifer reared under control culture conditions, elevated NaCl (157 mg L-1 Na), elevated CaCl2 (121 mg L-1 Ca), elevated Ca/MgSO4 (735 mg L-1 SO4). These conditions mirrored those from previously published physiological work. We also acutely exposed nymphs to dilute (50% dilution of culture water with deionized water) to explore proteomic changes in the gills in response to dilute conditions. We report 710 unique peptide sequences among treatment groups, including important apical ion transporters such as Ca-ATPase, Na/K ATPase, and V-ATPase. Treatment with elevated NaCl and Ca/MgSO4 appeared to cause more significant differential protein expression (452 and 345, respectively) compared to CaCl2 and dilute groups (134 and 17, respectively). Finally, we demonstrated the breadth of physiological functions in gills by exploring non-transport related pathways found in our dataset, including ATP synthesis, calcium signaling, and oxidative stress response. We discuss our results in the context of freshwater salinization and the challenges of working with non-model species without fully sequenced and annotated genomes.}, journal={ENVIRONMENTAL POLLUTION}, author={Orr, Sarah E. and Collins, Leonard B. and Jima, Dereje D. and Buchwalter, David B.}, year={2023}, month={Jan} }
 @article{cochran_orr_buchwalter_2022, title={Assessing the P-crit in relation to temperature and the expression of hypoxia associated genes in the mayfly, Neocloeon triangulifer}, volume={808}, ISSN={["1879-1026"]}, DOI={10.1016/j.scitotenv.2021.151743}, abstractNote={Hypoxia is a growing concern in aquatic ecosystems. Historically, scientists have used the Pcrit (the dissolved oxygen level below which an animal can no longer oxyregulate) to infer hypoxia tolerance across species. Here, we tested the hypothesis that the Pcrit is positively correlated with temperature in the mayfly, Neocloeon triangulifer. Cross-temperature comparisons showed a modest (r = 0.47), but significant (p < 0.0001) association between temperature and Pcrit despite relatively large interindividual variability (Coefficient of Variance (CV) = 39.9% at 18 °C). We used the expression of hypoxia-responsive genes EGL-9 (an oxygen sensing gene and modulator of HIF-1a activity) and LDH (a hypoxia indicator) to test whether oxygen partial pressure near the Pcrit stimulates expression of hypoxia-responsive genes. Neither gene was upregulated at oxygen levels above the estimated Pcrit, however, at or below the Pcrit estimates, expression of both genes was stimulated (~20- and ~3-fold change for EGL-9 and LDH, respectively). Finally, we evaluated the influence of hypoxic exposure time and pretreatment conditions on the mRNA expression levels of hypoxia-responsive genes. When larvae were exposed to a gradual reduction of DO, hypoxic gene expression was more robust than during instantaneous exposure to hypoxia. Our data provide modest support for traditional interpretation of the Pcrit as a physiologically meaningful shift from aerobic to anaerobic metabolism in N. triangulifer. However, we also discuss limitations of the Pcrit as a proxy measure of hypoxia tolerance at the species level.}, journal={SCIENCE OF THE TOTAL ENVIRONMENT}, author={Cochran, Jamie K. and Orr, Sarah E. and Buchwalter, David B.}, year={2022}, month={Feb} }
 @article{cochran_buchwalter_2022, title={The acclimatory response of the mayfly Neocloeon triangulifer to dilute conditions is linked to the plasticity of sodium transport}, volume={289}, ISSN={["1471-2954"]}, DOI={10.1098/rspb.2022.0529}, abstractNote={
            Relative to a growing body of knowledge about the negative consequences of freshwater salinization, little is known about how aquatic insects respond to progressively ion-poor conditions. Here, we examined life-history and physiological acclimation in
            Neocloeon triangulifer
            by rearing nymphs from 1-day post-egg hatch to adulthood across a gradient of decreasing Na concentrations (15, 8, 4, 2 and 1 mg l
            −1
            Na). We found no significant changes in survival, growth, development time and whole-body Na content across these treatments. Radiotracer data revealed that nymphs acclimated to their dilute exposures by increasing their rates of Na uptake and were able to maintain a relatively narrow range of uptake rates (±s.e.m.) of 38.5 ± 4.2 µg Na g
            −1
            h
            −1
            across all treatments. By contrast, the Na uptake rates observed in naive nymphs were much more concentration dependent. This acclimatory response is partially explained by differences in ionocyte counts on the gills of nymphs reared under different salinities. Acclimated nymphs were surprisingly less retentive of their sodium composition when subjected to deionized water challenge. By contrasting our findings with a previous
            N. triangulifer
            salinity acclimation study, we show a physiological affinity for dilute conditions in this emerging mayfly model.
          }, number={1979}, journal={PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES}, author={Cochran, Jamie K. K. and Buchwalter, David B. B.}, year={2022}, month={Jul} }
 @article{orr_cochran_wallace_gray_overmyer_buchwalter_2022, title={Weak differences in sensitivity to major ions by different larval stages of the mayfly Neocloeon triangulifer}, ISSN={["2161-9565"]}, DOI={10.1086/719359}, abstractNote={Freshwater salinization is a global ecological concern because of the alarming biodiversity declines associated with increases in major ion concentrations. Loss of mayfly diversity appears to be a common ecological response to anthropogenic salinization worldwide. Remarkably few regulatory standards exist to protect aquatic life from major ions, and antiquated approaches for setting such standards rely on traditional laboratory toxicity tests, which do not address sensitivities of mayflies at different larval stages. The lab-reared mayfly Neocloeon triangulifer (McDunnough, 1931) has emerged as one of the very few useful aquatic insect models for studying the effects of environmental stressors, including salinity, in the laboratory. Here, we asked if different larval life stages are differentially sensitivity to ion concentrations by conducting traditional 96-h toxicity tests with NaCl, CaCl2, and Ca/MgSO4. We used a general linear model to determine if survivorship differed among larval stages as well as ion type and concentration. We also calculated median lethal concentrations (LC50) for each larval stage. Larval sensitivity to NaCl decreased slightly with age (2–6, 9–13, and 17–21 d, with LC50 values of 401, 441, and 570 mg/L, respectively, when expressed as Na concentrations). Similarly, larval sensitivity to Ca/MgSO4 differed slightly among age groups (LC50 = 748, 1503, and 1439 mg/L, respectively, when expressed as SO4 concentrations). Reliable confidence intervals on LC50 values for CaCl2 could not be calculated because of high survivorship. However, our general linear model revealed that age played a moderate role in survival (p = 0.0065) across all salts of interest. To assess the potential changes in ion flux between larval stages, we used radiotracers (22Na, 35SO4, or 45Ca) in 18- and 25-d-old larvae and found no strong differences in ion uptake rates. We also qualitatively examined morphological differences between larval life stages, including the appearance of gills and number of ionocytes. Our results indicate that younger N. triangulifer larvae may be more sensitive to major ions than mature larvae. These results should be considered when experimentally using larger, late-stage N. triangulifer larvae to study the physiological effects and acute toxicity of salinity.}, journal={FRESHWATER SCIENCE}, author={Orr, Sarah E. and Cochran, Jamie K. and Wallace, Ian G. and Gray, Rachel W. and Overmyer, Gretta E. and Buchwalter, David B.}, year={2022}, month={Jun} }
 @article{guo_gustave_lu_he_tang_buchwalter_xu_2021, title={Periphyton enhances arsenic release and methylation at the soil-water interface of paddy soils}, volume={409}, ISSN={["1873-3336"]}, DOI={10.1016/j.jhazmat.2020.124946}, abstractNote={Periphyton is ubiquitous in rice paddy fields, however its role in paddy soil arsenic (As) biogeochemistry remains unexplored. In this study, microcosm incubations and extensive field sampling were used to better understand the roles of periphyton on As mobility and transformation at the soil-water interface. Microcosm incubations revealed that periphyton on the paddy soil surface enhanced As release to water and increased methylated As contents at the soil-water interface. Experimental additions of dissolved phosphate did not significantly affect these processes. The presence of periphyton increased the dissolved organic carbon (DOC) content of the surface soil which may have played a role in the increased As mobility. However, the increase in methylated As species at the soil-water interface is indicative of detoxification processes of As by periphyton. The results from the field study revealed a high abundance and diversity of As biotransformation and detoxification genes in periphyton. Genera of Kineosporia, Limisphaera, Ornatilinea, Ktedonosporobacter and Anaerolinea played key roles in shaping arsM harboring microbe communities in field periphyton. These results highlight the importance of periphyton in the behavior of As in paddy soils and can potentially facilitate improved management of As contamination in paddy soils.}, journal={JOURNAL OF HAZARDOUS MATERIALS}, author={Guo, Ting and Gustave, Williamson and Lu, Haiying and He, Yan and Tang, Xianjin and Buchwalter, David B. and Xu, Jianming}, year={2021}, month={May} }
 @article{verberk_buchwalter_kefford_2020, title={Energetics as a lens to understanding aquatic insect's responses to changing temperature, dissolved oxygen and salinity regimes}, volume={41}, ISSN={["2214-5753"]}, DOI={10.1016/j.cois.2020.06.001}, abstractNote={Assemblages of aquatic insects are structured by multiple biotic and abiotic conditions, including temperature, salinity and oxygen. Here we highlight recent developments in our understanding of how high temperatures, elevated salinities and low oxygen levels affect physiological processes, responses at the organismal level, and impacts on species interaction and community assembly. As aquatic insects may be exposed to multiple stressors, we review their sensitivity to interactive effects of multiple stressors. While each of these stressors may operate via different physiological mechanisms, they all influence the overall energy budget as well as the allocation of energy to competing functions such as homeostatic maintenance, growth, development and reproduction. As such, there is potential for interaction whereby one stressor may exacerbate the effect of another stressor. Integrating research on these stressors can provide a powerful approach for delineating the sensitivity of aquatic insects to multiple stressors and developing sound management practices.}, journal={CURRENT OPINION IN INSECT SCIENCE}, author={Verberk, Wilco C. E. P. and Buchwalter, David B. and Kefford, Ben J.}, year={2020}, month={Oct}, pages={46–53} }
 @article{ruiz-sobrino_martin-blanco_navarro_almudi_masiero_jimenez-caballero_buchwalter_funk_gattolliat_lemos_et al._2020, title={Space colonization by branching trachea explains the morphospace of a simple respiratory organ}, volume={462}, ISSN={["1095-564X"]}, DOI={10.1016/j.ydbio.2020.02.005}, abstractNote={Branching morphogenesis helps increase the efficiency of gas and liquid transport in many animal organs. Studies in several model organisms have highlighted the molecular and cellular complexity behind branching morphogenesis. To understand this complexity, computational models have been developed with the goal of identifying the “major rules” that globally explain the branching patterns. These models also guide further experimental exploration of the biological processes that execute and maintain these rules. In this paper we introduce the tracheal gills of mayfly (Ephemeroptera) larvae as a model system to study the generation of branched respiratory patterns. First, we describe the gills of the mayfly Cloeon dipterum, and quantitatively characterize the geometry of its branching trachea. We next extend this characterization to those of related species to generate the morphospace of branching patterns. Then, we show how an algorithm based on the “space colonization” concept (SCA) can generate this branching morphospace via growth towards a hypothetical attractor molecule (M). SCA differs from other branch-generating algorithms in that the geometry generated depends to a great extent on its perception of the “external” space available for branching, uses few rules and, importantly, can be easily translated into a realistic “biological patterning algorithm”. We identified a gene in the C. dipterum genome (Cd-bnl) that is orthologous to the fibroblast growth factor branchless (bnl), which stimulates growth and branching of embryonic trachea in Drosophila. In C. dipterum, this gene is expressed in the gill margins and areas of finer tracheolar branching from thicker trachea. Thus, Cd-bnl may perform the function of M in our model. Finally, we discuss this general mechanism in the context of other branching pattern-generating algorithms.}, number={1}, journal={DEVELOPMENTAL BIOLOGY}, author={Ruiz-Sobrino, A. and Martin-Blanco, C. A. and Navarro, T. and Almudi, I and Masiero, G. and Jimenez-Caballero, M. and Buchwalter, D. B. and Funk, D. H. and Gattolliat, J. L. and Lemos, M. C. and et al.}, year={2020}, month={Jun}, pages={50–59} }
 @article{chou_jima_funk_jackson_sweeney_buchwalter_2020, title={Transcriptomic and life history responses of the mayfly Neocloeon triangulifer to chronic diel thermal challenge}, volume={10}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-020-75064-y}, abstractNote={Abstract}, number={1}, journal={SCIENTIFIC REPORTS}, author={Chou, Hsuan and Jima, Dereje D. and Funk, David H. and Jackson, John K. and Sweeney, Bernard W. and Buchwalter, David B.}, year={2020}, month={Nov} }
 @article{macaulay_buchwalter_matthaei_2020, title={Water temperature interacts with the insecticide imidacloprid to alter acute lethal and sublethal toxicity to mayfly larvae}, volume={54}, ISSN={["1175-8805"]}, DOI={10.1080/00288330.2019.1614961}, abstractNote={ABSTRACT Increased temperatures and exposure to agricultural insecticides are increasingly threatening freshwater ecosystems worldwide. However, their combined effects are still poorly understood. We investigated the individual and interactive effects of water temperature and imidacloprid, the most widely used neonicotinoid insecticide, on larvae of two New Zealand mayflies, Deleatidium spp. and Coloburiscus humeralis. Ninety-six-hour bioassays with imidacloprid were performed at 9, 12, 15, 18, 21 and 24°C, in a full-factorial design. Mayfly survivorship and sub-lethal responses of impairment and moulting were recorded. We documented synergistically increased mayfly mortality and immobility with exposure to imidacloprid at higher temperatures, implying temperature-enhanced toxicity of imidacloprid. Survivorship of both mayflies was synergistically reduced by the combination of imidacloprid exposure and increasing temperatures. The same interaction also affected mobility of C. humeralis and moulting frequency of Deleatidium. Our findings suggest that developing a more thorough understanding of temperature-contaminant interactions may be important to allow better protection of aquatic ecosystems.}, number={1}, journal={NEW ZEALAND JOURNAL OF MARINE AND FRESHWATER RESEARCH}, author={Macaulay, Samuel J. and Buchwalter, David B. and Matthaei, Christoph D.}, year={2020}, pages={115–130} }
 @article{buchwalter_scheibener_chou_soucek_elphick_2019, title={Are sulfate effects in the mayfly Neocloeon triangulifer driven by the cost of ion regulation?}, volume={374}, ISSN={["1471-2970"]}, DOI={10.1098/rstb.2018.0013}, abstractNote={
            Elevated major ion concentrations in streams are commonly observed as a consequence of resource extraction, de-icing and other anthropogenic activities. Ecologists report biodiversity losses associated with increasing salinity, with mayflies typically being highly responsive to increases of different major ions. In this study, we evaluated the performance of the mayfly
            Neocloeon triangulifer
            reared for its entire larval phase in a gradient of sulfate concentrations. Two natural waters were amended with SO
            4
            as a blend of CaSO
            4
            and MgSO
            4
            and exposures ranged from 5 to 1500 mg l
            –1
            SO
            4.
            Survival (per cent successful emergence to the subimago stage) was significantly reduced at the highest SO
            4
            concentration in both waters, while development was significantly delayed at 667 mg l
            −1
            SO
            4
            . Final sub-adult body weights were consistent across treatments, except at the highest treatment concentration. Despite evidence for sulfate uptake rates increasing with exposure concentrations and not being saturated at even extremely high SO
            4
            concentrations, total body sulfur changed little in subimagos. Together, these results suggest that elevated SO
            4
            imposes an energetic demand associated with maintaining homeostasis that is manifested primarily as reduced growth rates and associated developmental delays. We identified two genes related to sulfate transport in
            N. triangulifer
            .
          }, number={1764}, journal={PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES}, author={Buchwalter, David and Scheibener, Shane and Chou, Hsuan and Soucek, David and Elphick, James}, year={2019}, month={Jan} }
 @article{green_hoyo_mattingly_luo_tzeng_murphy_buchwalter_planchart_2018, title={Cadmium exposure increases the risk of juvenile obesity: a human and zebrafish comparative study}, volume={42}, ISSN={0307-0565 1476-5497}, url={http://dx.doi.org/10.1038/S41366-018-0036-Y}, DOI={10.1038/S41366-018-0036-Y}, abstractNote={Human obesity is a complex metabolic disorder disproportionately affecting people of lower socioeconomic strata, and ethnic minorities, especially African Americans and Hispanics. Although genetic predisposition and a positive energy balance are implicated in obesity, these factors alone do not account for the excess prevalence of obesity in lower socioeconomic populations. Therefore, environmental factors, including exposure to pesticides, heavy metals, and other contaminants, are agents widely suspected to have obesogenic activity, and they also are spatially correlated with lower socioeconomic status. Our study investigates the causal relationship between exposure to the heavy metal, cadmium (Cd), and obesity in a cohort of children and in a zebrafish model of adipogenesis.An extensive collection of first trimester maternal blood samples obtained as part of the Newborn Epigenetics Study (NEST) was analyzed for the presence of Cd, and these results were cross analyzed with the weight-gain trajectory of the children through age 5 years. Next, the role of Cd as a potential obesogen was analyzed in an in vivo zebrafish model.Our analysis indicates that the presence of Cd in maternal blood during pregnancy is associated with increased risk of juvenile obesity in the offspring, independent of other variables, including lead (Pb) and smoking status. Our results are recapitulated in a zebrafish model, in which exposure to Cd at levels approximating those observed in the NEST study is associated with increased adiposity.Our findings identify Cd as a potential human obesogen. Moreover, these observations are recapitulated in a zebrafish model, suggesting that the underlying mechanisms may be evolutionarily conserved, and that zebrafish may be a valuable model for uncovering pathways leading to Cd-mediated obesity in human populations.}, number={7}, journal={International Journal of Obesity}, publisher={Springer Science and Business Media LLC}, author={Green, Adrian J. and Hoyo, Cathrine and Mattingly, Carolyn J. and Luo, Yiwen and Tzeng, Jung-Ying and Murphy, Susan K. and Buchwalter, David B. and Planchart, Antonio}, year={2018}, month={Feb}, pages={1285–1295} }
 @misc{buchwalter_2018, title={Ecotoxicology Essentials: Environmental Contaminants and Their Biological Effects on Animals and Plants. By Donald W. Sparling. Academic Press. Amsterdam (The Netherlands) and Boston (Massachusetts): Elsevier. $79.95 (paper). ix + 490 p.; ill.; index. ISBN: 978-0-12-801947-4. 2016.}, volume={93}, ISSN={0033-5770 1539-7718}, url={http://dx.doi.org/10.1086/696739}, DOI={10.1086/696739}, abstractNote={Previous articleNext article No AccessEcologyEcotoxicology Essentials: Environmental Contaminants and Their Biological Effects on Animals and Plants. By Donald W. Sparling. Academic Press. Amsterdam (The Netherlands) and Boston (Massachusetts): Elsevier. $79.95 (paper). ix + 490 p.; ill.; index. ISBN: 978-0-12-801947-4. 2016.David B. BuchwalterDavid B. BuchwalterBiological Sciences, North Carolina State University, Raleigh, North Carolina Search for more articles by this author Biological Sciences, North Carolina State University, Raleigh, North CarolinaPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 93, Number 1March 2018 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/696739 Views: 66Total views on this site For permission to reuse, please contact [email protected]PDF download Crossref reports no articles citing this article.}, number={1}, journal={The Quarterly Review of Biology}, publisher={University of Chicago Press}, author={Buchwalter, David B.}, year={2018}, month={Mar}, pages={29–29} }
 @article{lopez_silva_webb_hesterberg_buchwalter_2018, title={Periphyton and abiotic factors influencing arsenic speciation in aquatic environments}, volume={37}, ISSN={["1552-8618"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85039735474&partnerID=MN8TOARS}, DOI={10.1002/etc.4025}, abstractNote={Abstract}, number={3}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Lopez, Adeline R. and Silva, Silmara Costa and Webb, Samuel M. and Hesterberg, Dean and Buchwalter, David B.}, year={2018}, month={Mar}, pages={903–913} }
 @article{chou_pathmasiri_deese-spruill_sumner_jima_funk_jackson_sweeney_buchwalter_2018, title={The Good, the Bad, and the Lethal: Gene Expression and Metabolomics Reveal Physiological Mechanisms Underlying Chronic Thermal Effects in Mayfly Larvae (Neocloeon triangulifer)}, volume={6}, ISSN={["2296-701X"]}, DOI={10.3389/fevo.2018.00027}, abstractNote={Temperature dictates the performance of aquatic ectotherms. However, the physiological and biochemical processes that drive thermally-mediated life history patterns (and limits) remain poorly understood because they are rarely studied simultaneously. In our previous work, we have established life history outcomes (e.g. survivorship, development time, growth rates and fitness) in mayflies (Neocloeon triangulifer) reared at static temperatures ranging from 14°C - 30°C at 2°C intervals. In this study, we conducted biochemical measurements (RT-qPCR of select genes and targeted, quantitative metabolomic profiling) on N. triangulifer mature larvae reared at temperatures associated with excellent survival and fitness (22-24°C), compromised survival and fitness (28°C), and chronic lethality (30°C -larvae survived for a few weeks but failed to emerge to adulthood). Patterns of gene expression were similar to those observed in acute ramping experiments reported previously: larvae reared at 30°C resulted in significant upregulation in the thermally responsive gene HEAT SHOCK PROTEIN 90 (HSP90) but no significant changes in hypoxia responsive genes (EGG LAYING DEFECTIVE 9 (EGL-9) and LACTATE DEHYDROGENASE (LDH)). Additionally, primers for genes associated with energy: INSULIN RECEPTOR (IR), mechanistic TARGET OF RAPAMYCIN (mTOR) and TREHALOSE 6 PHOSPHATE SYNTHASE (T6PS) were developed for this study. IR and mTOR were significantly upregulated while T6PS showed trend of downregulation in larvae reared at 30°C. Metabolomic profiles revealed general depletion of lipids and acylcarnitines in larvae exposed to chronic thermal stress, suggesting that larvae were energetically challenged despite continuous access to food. For example, concentrations of lysoPhosphatidylcholine (lysoPC) a C20:3 decreased as fitness decreased with increasing temperature (2.3 fold and 2.4 fold at 28 and 30°C relative to controls). Tissue concentrations of the biogenic amine histamine increased 2.1 and 3.1 fold with increasing temperature, and were strongly and negatively correlated with performance. Thus, both histamine and lysoPC a C20:3 are potential biomarkers of thermal stress. Taken together, our results primarily associate energetic challenge with thermally mediated fitness reduction in N. triangulifer.}, journal={FRONTIERS IN ECOLOGY AND EVOLUTION}, author={Chou, Hsuan and Pathmasiri, Wimal and Deese-spruill, Jocelin and Sumner, Susan J. and Jima, Dereje D. and Funk, David H. and Jackson, John K. and Sweeney, Bernard W. and Buchwalter, David B.}, year={2018}, month={Mar} }
 @article{sweeney_funk_camp_buchwalter_jackson_2018, title={Why adult mayflies of Cloeon dipterum (Ephemeroptera:Baetidae) become smaller as temperature warms}, volume={37}, ISSN={2161-9549 2161-9565}, url={http://dx.doi.org/10.1086/696611}, DOI={10.1086/696611}, abstractNote={We reared Cloeon dipterum from egg hatch to adult at 10 constant temperatures (12.1–33.5°C) to test 3 hypotheses (thermal equilibrium hypothesis, temperature size rule [TSR], and O2- and capacity-limited thermal tolerance [OCLTT]) that account for variation in life-history traits across thermal gradients. Male and female adult size declined ~67 and 78% and larval development time declined ~88% with warming; chronic survivorship (thermal limit for population growth) was highest from 16.2 to 23.9°C (mean = 85%) and declined to 0 at 33.5°C; thresholds for 0 growth and development were 10.0 and 10.7°C, respectively; peak rate of population increase (r) occurred at 27.8°C; rates of growth and development were maximal at 30°C; fecundity was greatest at 12.1°C; and between 14.3 and 30°C, growth and development rates increased linearly and the number of degree days (>10.7°C) to complete development was nearly constant (mean = 271). Acute survivorship during short-term thermal ramping was 0 at 40°C. Warming temperature caused development rate to increase proportionately faster than growth rate; male and female adult size to decrease as per TSR, with adult females ~5× larger at 12.1 than 31.7°C; adult size to decrease proportionately more for females than males; and fecundity to decrease proportionately more than adult female size. TSR was related to differences in the responses of growth and development rates at temperatures above thresholds rather than to thresholds for growth or development per se. Respirometry suggested that OCLTT is more applicable to acute than chronic thermal limits. Cloeon dipterum appears to have a thermal ‘acclimation zone’ between 14.3 and 30°C where development and growth rates change linearly and degree-day requirements to complete metamorphosis are constant. The optimum temperature is ~27.8°C where r is maximum. We propose 5 hypotheses to explain these patterns.}, number={1}, journal={Freshwater Science}, publisher={University of Chicago Press}, author={Sweeney, Bernard W. and Funk, David H. and Camp, Allison A. and Buchwalter, David B. and Jackson, John K.}, year={2018}, month={Mar}, pages={64–81} }
 @article{lopez_funk_buchwalter_2017, title={Arsenic (V) bioconcentration kinetics in freshwater macroinvertebrates and periphyton is influenced by pH}, volume={224}, ISSN={["1873-6424"]}, DOI={10.1016/j.envpol.2016.12.066}, abstractNote={Arsenic is an important environmental pollutant whose speciation and mobility in freshwater food webs is complex. Few studies have characterized uptake and efflux rates of arsenic in aquatic benthic invertebrates. Further, we lack a fundamental understanding of how pH influences uptake kinetics in these organisms or how this key environmental variable could alter dietary exposure for primary consumers. Here we used a radiotracer approach to characterize arsenate accumulation dynamics in benthic invertebrates, the influence of pH on uptake in a subset of these organisms, and the influence of pH on uptake of arsenate by periphyton - an important food source at the base of aquatic food webs. Uptake rate constants (Ku) from aqueous exposure were modest, ranging from ∼0.001 L g−1d−1 in three species of mayfly to 0.06 L g−1d−1in Psephenus herricki. Efflux rate constants ranged from ∼0.03 d−1 in Corbicula fluminea to ∼0.3 d−1 in the mayfly Isonychia sp, and were generally high. Arsenate uptake decreased with increasing pH, which may be a function of increased adsorption at lower pHs. A similar but much stronger correlation was observed for periphyton where Ku decreased from ∼3.0 L g−1d−1 at 6.5 pH to ∼0.7 L g−1d−1 at 8.5 pH, suggesting that site specific pH could significantly alter arsenic exposure, particularly for primary consumers. Together, these findings shed light on the complexity of arsenic bioavailability and help explain observed differences reported in the literature.}, journal={ENVIRONMENTAL POLLUTION}, author={Lopez, Adeline R. and Funk, David H. and Buchwalter, David B.}, year={2017}, month={May}, pages={82–88} }
 @article{peterson_buchwalter_kerby_lefauve_varian-ramos_swaddle_2017, title={Integrative behavioral ecotoxicology: bringing together fields to establish new insight to behavioral ecology, toxicology, and conservation}, volume={63}, ISSN={["2396-9814"]}, DOI={10.1093/cz/zox010}, abstractNote={Abstract The fields of behavioral ecology, conservation science, and environmental toxicology individually aim to protect and manage the conservation of wildlife in response to anthropogenic stressors, including widespread anthropogenic pollution. Although great emphasis in the field of toxicology has been placed on understanding how single pollutants affect survival, a comprehensive, interdisciplinary approach that includes behavioral ecology is essential to address how anthropogenic compounds are a risk for the survival of species and populations in an increasingly polluted world. We provide an integrative framework for behavioral ecotoxicology using Tinbergen’s four postulates (causation and mechanism, development and ontogeny, function and fitness, and evolutionary history and phylogenetic patterns). The aims of this review are: 1) to promote an integrative view and re-define the field of integrative behavioral ecotoxicology; 2) to demonstrate how studying ecotoxicology can promote behavior research; and 3) to identify areas of behavioral ecotoxicology that require further attention to promote the integration and growth of the field.}, number={2}, journal={CURRENT ZOOLOGY}, author={Peterson, Elizabeth K. and Buchwalter, David B. and Kerby, Jacob L. and LeFauve, Matthew K. and Varian-Ramos, ClaireW. and Swaddle, John P.}, year={2017}, month={Apr}, pages={185–194} }
 @article{chou_funk_buchwalter_2017, title={Keep breathing: Linking respiration to thermally regulated life history outcomes in the Mayfly Neocloeon triangulifer}, volume={57}, journal={Integrative and Comparative Biology}, author={Chou, H. and Funk, D. and Buchwalter, D.}, year={2017}, pages={E225–225} }
 @article{chou_pathmasiri_sumner_buchwalter_2017, title={Linking physiological mechanisms to thermally driven life history outcomes in the Mayfly Neocloeon triangulifer}, volume={57}, journal={Integrative and Comparative Biology}, author={Chou, H. and Pathmasiri, W. and Sumner, S. and Buchwalter, D.}, year={2017}, pages={E225–225} }
 @article{chou_pathmasiri_deese-spruill_sumner_buchwalter_2017, title={Metabolomics reveal physiological changes in mayfly larvae (Neocloeon triangulifer) at ecological upper thermal limits}, volume={101}, ISSN={["1879-1611"]}, DOI={10.1016/j.jinsphys.2017.07.008}, abstractNote={Aquatic insects play critical roles in freshwater ecosystems and temperature is a fundamental driver of species performance and distributions. However, the physiological mechanisms that determine the thermal performance of species remain unclear. Here we used a metabolomics approach to gain insights into physiological changes associated with a short-term, sublethal thermal challenge in the mayfly Neocloeon triangulifer (Ephemeroptera: Baetidae). Larvae were subjected to a thermal ramp (from 22 to 30 °C at a rate of 1 °C/h) and metabolomics analysis (both Nuclear Magnetic Resonance (NMR) Spectroscopy and Gas Chromatography coupled Time-of-Flight Mass Spectrometry (GC-TOF-MS)) indicated that processes related to energetics (sugar metabolism) and membrane stabilization primarily differentiated heat treated larvae from controls. Limited evidence of anaerobic metabolism was observed in the heat treated larvae at 30 °C, a temperature that is chronically lethal to larvae.}, journal={JOURNAL OF INSECT PHYSIOLOGY}, author={Chou, Hsuan and Pathmasiri, Wimal and Deese-Spruill, Jocelin and Sumner, Susan and Buchwalter, David B.}, year={2017}, pages={107–112} }
 @article{buchwalter_clements_luoma_2017, title={Modernizing Water Quality Criteria in the United States: A Need to Expand the Definition of Acceptable Data}, volume={36}, ISSN={["1552-8618"]}, DOI={10.1002/etc.3654}, abstractNote={Abstract}, number={2}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Buchwalter, David B. and Clements, William H. and Luoma, Samuel N.}, year={2017}, month={Feb}, pages={285–291} }
 @article{scheibener_rivera_hesterberg_duckworth_buchwalter_2017, title={Periphyton uptake and trophic transfer of coal fly-ash-derived trace elements}, volume={36}, ISSN={["1552-8618"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85024902922&partnerID=MN8TOARS}, DOI={10.1002/etc.3864}, abstractNote={Abstract}, number={11}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Scheibener, Shane A. and Rivera, Nelson A. and Hesterberg, Dean and Duckworth, Owen W. and Buchwalter, David B.}, year={2017}, month={Nov}, pages={2991–2996} }
 @article{kim_chou_funk_jackson_sweeney_buchwalter_2017, title={Physiological responses to short-term thermal stress in mayfly (Neocloeon triangulifer) larvae in relation to upper thermal limits}, volume={220}, ISSN={["1477-9145"]}, DOI={10.1242/jeb.156919}, abstractNote={ABSTRACT}, number={14}, journal={JOURNAL OF EXPERIMENTAL BIOLOGY}, author={Kim, Kyoung Sun and Chou, Hsuan and Funk, David H. and Jackson, John K. and Sweeney, Bernard W. and Buchwalter, David B.}, year={2017}, month={Jul}, pages={2598–2605} }
 @misc{buchwalter_clements_luoma_2017, title={Response to Buchwalter et al. further considerations for modernizing water quality criteria in the United States and elsewhere reply}, volume={36}, number={6}, journal={Environmental Toxicology and Chemistry}, author={Buchwalter, D. and Clements, W. H. and Luoma, S.}, year={2017}, pages={1425–1426} }
 @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{buchwalter_clements_luoma_2017, title={The authors’ reply}, volume={36}, ISSN={0730-7268}, url={http://dx.doi.org/10.1002/ETC.3813}, DOI={10.1002/ETC.3813}, abstractNote={We thankWarne et al. [1] for their thoughtful comments in the Letter to the Editor “Response to Buchwalter et al. Further considerations for modernizing water quality criteria in the UnitedStates and elsewhere.”The authorsmake several excellent points that merit a broader discussion. Although our original ideas were focused specifically on water quality criteria (WQC) in the Unites States [2], it is apparent that many of the issues we discussed are pertinent to the challenge of creating scientifically defensible environmental standards throughout the world. Warne et al. raise 2 central tenants in their comments. The first is that some of our suggestions have already been adopted in other jurisdictions. This is encouraging and demonstrates the feasibility of including a broader array of information for informing WQC in the United States. For example, the European Union and Australia and New Zealand use of mesocosm data demonstrates that when established data quality objectives are met, these data can help inform water quality benchmarks. The United States can certainly benefit from such experience. That said, we would never advocate deriving WQC from only a single line of evidence. Our intent was to encourage the incorporation of all relevant knowledge streams rather than rely on information derived from a single methodology. The second tenant that Warne et al. raise is an important one: Achieving “the right balance between a goal of ever-increasingly accurate benchmarks for a very limited number of chemicals (e.g., the United States hasWQC for 40 chemicals) and having less accurate default benchmarks for far more chemicals (e.g., Australia and New Zealand have guideline values for over 300 chemicals).” This issue of quality or “accuracy” versus quantity of benchmarks/criteria is important when we consider that there are literally thousands of high volume chemicals used in commerce that have no criteria or benchmarks. In this context, our suggestion that data from more species be included in WQC derivation might also appear to represent an obstacle for generating new criteria, particularly because the United States does not use “less accurate” default benchmarks. From our perspective, the question becomes “How much uncertainty are we willing to accept?” In this regard, Warne et al. make the important distinction between United States WQC, which are essentially pass/fail values, and the Australia and New Zealand guidelines, which are only one of multiple lines of evidence used to assess water quality. We agree that the acceptable level of uncertainty will be greater in situations where an exceedance simply triggers further site-specific investigation. Warne et al. “support the call for an expansion of the types of organisms used to derive benchmarks, but do not support the expansion of a prescribed list of organism types.”We agree that a prescribed “one size fits all” list of required species for all chemicals would be counterproductive. For example, it would make no sense to require an exhaustive understanding of the sensitivity of fishes to herbicides when plants are likely to be most vulnerable to herbicide exposures. However, there are some common-sense approaches that could be taken to reduce uncertainty. Current US Environmental Protection Agency guidelines [3] highlight the importance of habitat considerations (warm vs cold waterfish; benthic vs pelagic crustaceans). An updated version of the guidelines could consider requiring toxicity data from taxa that are considered. First, species integral to ecosystem function (e.g., insects in freshwater ecosystems; keystone or foundation species). While all species play important ecological roles, some faunal groups are clearly more important to ecosystem function than others. Insects in freshwater ecosystems provide a perfect example of this. If we randomly sampled animal life in a United States stream, it is highly likely that>90% of the samples would be insects. We are not advocating that insects are represented in toxicity datasets commensurate with their occurrence in nature (see Brix et al. [4]), because this is not feasible. However, we can do much better than only requiring a single insect species. We contend that any freshwater criterion or benchmark that lacks insect representatives (beyond notoriously tolerant midges) will have a great deal of uncertainty associated with it. Second, species of special conservation concern (e.g., freshwater mussels). In the United States, freshwater mussels are becoming extinct before our very eyes. It would make sense to have some knowledge of potential hazards of a given contaminant to representatives of faunal groups that are known to be at risk of extinction. Third, species of cultural and/or economic importance? (e.g., salmonids). Fourth, species likely to be particularly susceptible to a particular chemical? (e.g., plants exposed to herbicides). We are pleased that Warne et al. recognize the importance of trophic exposure pathways for bioaccumulative contaminants, and their examples of perfluorooctane sulfonate and perfluorooctanoic acid are quite relevant. However, it is unclear ifWarne et al. advocate for addressing this important issue in toxicity experiments, or if they favor the designation of a benchmark as underprotective. It is interesting that the overfeeding of Ceriodaphnia and copepods in standard chronic tests is cited as an argument against providing dietary exposures. This seems to be more of a test protocol issue than a philosophical issue. Previous work with the effects of food rations on selenium (Se) toxicity in mayflies [5] suggested that sensitivity was negatively associated with feeding regime. Mayflies that had access to larger rations of Se contaminated food were less sensitive than mayflies that were given reduced rations. This same negative association between food rations and sensitivity has been observed in Daphnia for lead [6], cadmium [7], and fenvalerate [8], and in the amphipod Paramoera walker for copper [9] in multiple stressor experiments. Moreover, reduced assimilation efficiency for elements such as Se, Ag, Am, Co, and Zn are reported byWang et al. [10] and by Van Campenhout for Zn [11]. Finally, feeding inhibition is commonly observed when the diet is contaminated [12]. Far less effort has been invested in development of protocols and endpoints for dietary exposure than for traditional exposures. The concern of Warne et al. Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/etc.3813 Environmental Toxicology and Chemistry, Vol. 36, No. 6, pp. 1425–1426, 2017 # 2017 SETAC Printed in the USA}, number={6}, journal={Environmental Toxicology and Chemistry}, publisher={Wiley}, author={Buchwalter, David and Clements, William H. and Luoma, Sam}, year={2017}, month={May}, pages={1425–1426} }
 @article{lopez_hesterberg_funk_buchwalter_2016, title={Bioaccumulation Dynamics of Arsenate at the Base of Aquatic Food Webs}, volume={50}, ISSN={["1520-5851"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84975471905&partnerID=MN8TOARS}, DOI={10.1021/acs.est.6b01453}, abstractNote={Periphyton is an important food source at the base of freshwater ecosystems that tends to bioconcentrate trace elements making them trophically available. The potential for arsenic-a trace element of particular concern due to its widespread occurrence, toxicity, and carcinogenicity-to bioconcentrate in periphyton and thus be available to benthic grazers is less well characterized. To better understand arsenate bioaccumulation dynamics in lotic food webs, we used a radiotracer approach to characterize accumulation in periphyton and subsequent trophic transfer to benthic grazers. Periphyton bioconcentrated As between 3,200-9,700-fold (dry weight) over 8 days without reaching steady state, suggesting that periphyton is a major sink for arsenate. However, As-enriched periphyton as a food source for the mayfly Neocloeon triangulifer resulted in negligible As accumulation in a full lifecycle exposure. Additional studies estimate dietary assimilation efficiency in several primary consumers ranging from 22% in the mayfly N. triangulifer to 75% in the mayfly Isonychia sp. X-ray fluorescence mapping revealed that As was predominantly associated with iron oxides in periphyton. We speculate that As adsorption to Fe in periphyton may play a role in reducing dietary bioavailability. Together, these results suggest that trophic movement of As in lotic food webs is relatively low, though species differences in bioaccumulation patterns are important.}, number={12}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Lopez, Adeline R. and Hesterberg, Dean R. and Funk, David H. and Buchwalter, David B.}, year={2016}, month={Jun}, pages={6556–6564} }
 @article{camp_buchwalter_2016, title={Can't take the heat: Temperature-enhanced toxicity in the mayfly Isonychia bicolor exposed to the neonicotinoid insecticide imidacloprid}, volume={178}, ISSN={["1879-1514"]}, DOI={10.1016/j.aquatox.2016.07.011}, abstractNote={Neonicotinoid insecticide usage has increased globally in recent decades. Neonicotinoids, such as imidacloprid, are potent insect neurotoxicants that may pose a threat to non-target aquatic organisms, such as aquatic insects. In nature, insects typically live in thermally fluctuating conditions, which may significantly alter both contaminant exposures and affects. Here we investigate the relationship between temperature and time-to-effect for imidacloprid toxicity with the aquatic insect Isonychia bicolor, a lotic mayfly. Additionally, we examined the mechanisms driving temperature-enhanced toxicity including metabolic rate, imidacloprid uptake rate, and tissue bioconcentration. Experiments included acute toxicity tests utilizing sublethal endpoints and mortality, as well as respirometry and radiotracer assays with [(14)C] imidacloprid. Further, we conducted additional uptake experiments with a suite of aquatic invertebrates (including I. bicolor, Neocloeon triangulifer, Macaffertium modestum, Pteronarcys proteus, Acroneuria carolinensis, and Pleuroceridae sp) to confirm and contextualize our findings from initial experiments. The 96h EC50 (immobility) for I. bicolor at 15°C was 5.81μg/L which was approximately 3.2 fold lower than concentrations associated with 50% mortality. Assays examining the impact of temperature were conducted at 15, 18, 21, and 24°C and demonstrated that time-to-effect for sublethal impairment and immobility was significantly decreased with increasing temperature. Uptake experiments with [(14)C] imidacloprid revealed that initial uptake rates were significantly increased with increasing temperature for I. bicolor, as were oxygen consumption rates. Further, in the separate experiment with multiple species across temperatures 15, 20, and 25°C, we found that all the aquatic insects tested had significantly increased imidacloprid uptake with increasing temperatures, with N. triangulifer accumulating the most imidacloprid on a mass-specific basis. Our acute toxicity results highlight the importance of evaluating sublethal endpoints, as profound impairments of motor function were evident far before mortality. Further, we demonstrate that temperature is a powerful modulator of sublethal toxicity within a range of environmentally relevant temperatures, impacting both uptake rates and metabolic rates of I. bicolor. Finally, we show that temperature alters imidacloprid uptake across a range of species, highlighting the physiological variation present within aquatic invertebrate communities and the challenge associated with relying solely on surrogate species. Taken together, this research points to the need to consider the role of temperature in toxicity assessments.}, journal={AQUATIC TOXICOLOGY}, author={Camp, A. A. and Buchwalter, D. B.}, year={2016}, month={Sep}, pages={49–57} }
 @article{scheibener_richardi_buchwalter_2016, title={Comparative sodium transport patterns provide clues for understanding salinity and metal responses in aquatic insects}, volume={171}, ISSN={["1879-1514"]}, DOI={10.1016/j.aquatox.2015.12.006}, abstractNote={The importance of insects in freshwater ecosystems has led to their extensive use in ecological monitoring programs. As freshwater systems are increasingly challenged by salinization and metal contamination, it is important to understand fundamental aspects of aquatic insect physiology (e.g., osmoregulatory processes) that contribute to insect responses to these stressors. Here we compared the uptake dynamics of Na as NaCl, NaHCO3 and Na2SO4 in the caddisfly Hydropsyche betteni across a range of Na concentrations (0.06–15.22 mM) encompassing the vast majority of North American freshwater ecosystems. Sulfate as the major anion resulted in decreased Na uptake rates relative to the chloride and bicarbonate salts. A comparison of Na (as NaHCO3) turnover rates in the caddisfly Hydropsyche sparna and the mayfly Maccaffertium sp. revealed different patterns in the 2 species. Both species appeared to tightly regulate their whole body sodium concentrations (at ∼47 ± 1.8 μmol/g wet wt) across a range of Na concentrations (0.06–15.22 mM) over 7 days. However, at the highest Na concentration (15.22 mM), Na uptake rates in H. sparna (419.1 μM Na g−1 hr−1 wet wt) appeared close to saturation while Na uptake rates in Maccaffertium sp. were considerably faster (715 g μM Na g−1 hr−1 wet wt) and appeared to not be close to saturation. Na efflux studies in H. sparna revealed that loss rates are commensurate with uptake rates and are responsive to changes in water Na concentrations. A comparison of Na uptake rates (at 0.57 mM Na) across 9 species representing 4 major orders (Ephemeroptera, Plecoptera, Trichoptera and Diptera) demonstrated profound physiological differences across species after accounting for the influence of body weight. Faster Na uptake rates were associated with species described as being sensitive to salinization in field studies. The metals silver (Ag) and copper (Cu), known to be antagonistic to Na uptake in other aquatic taxa did not generally exhibit this effect in aquatic insects. Ag only reduced Na uptake at extremely high concentrations, while Cu generally stimulated Na uptake in aquatic insects, rather than suppress it. These results help explain the lack of insect responses to dissolved metal exposures in traditional toxicity testing and highlight the need to better understand fundamental physiological processes in this ecologically important faunal group.}, journal={AQUATIC TOXICOLOGY}, author={Scheibener, S. A. and Richardi, V. S. and Buchwalter, D. B.}, year={2016}, month={Feb}, pages={20–29} }
 @misc{kefford_buchwalter_canedo-argueelles_davis_duncan_hoffmann_thompson_2016, title={Salinized rivers: degraded systems or new habitats for salt-tolerant faunas?}, volume={12}, ISSN={["1744-957X"]}, DOI={10.1098/rsbl.2015.1072}, abstractNote={Anthropogenic salinization of rivers is an emerging issue of global concern, with significant adverse effects on biodiversity and ecosystem functioning. Impacts of freshwater salinization on biota are strongly mediated by evolutionary history, as this is a major factor determining species physiological salinity tolerance. Freshwater insects dominate most flowing waters, and the common lotic insect orders Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies) are particularly salt-sensitive. Tolerances of existing taxa, rapid adaption, colonization by novel taxa (from naturally saline environments) and interactions between species will be key drivers of assemblages in saline lotic systems. Here we outline a conceptual framework predicting how communities may change in salinizing rivers. We envision that a relatively small number of taxa will be saline-tolerant and able to colonize salinized rivers (e.g. most naturally saline habitats are lentic; thus potential colonizers would need to adapt to lotic environments), leading to depauperate communities in these environments.}, number={3}, journal={BIOLOGY LETTERS}, author={Kefford, Ben J. and Buchwalter, David and Canedo-Argueelles, Miguel and Davis, Jenny and Duncan, Richard P. and Hoffmann, Ary and Thompson, Ross}, year={2016}, month={Mar} }
 @article{canedo-argueelles_hawkins_kefford_schaefer_dyack_brucet_buchwalter_dunlop_froer_lazorchak_et al._2016, title={Saving freshwater from salts}, volume={351}, ISSN={["1095-9203"]}, DOI={10.1126/science.aad3488}, abstractNote={Ion-specific standards are needed to protect biodiversity}, number={6276}, journal={SCIENCE}, author={Canedo-Argueelles, M. and Hawkins, C. P. and Kefford, B. J. and Schaefer, R. B. and Dyack, B. J. and Brucet, S. and Buchwalter, D. and Dunlop, J. and Froer, O. and Lazorchak, J. and et al.}, year={2016}, month={Feb}, pages={914–916} }
 @article{weaver_lazorchak_struewing_decelles_funk_buchwalter_johnson_2015, title={Part 1: Laboratory culture of Centroptilum triangulifer (Ephemeroptera: Baetidae) using a defined diet of three diatoms}, volume={139}, ISSN={["1879-1298"]}, DOI={10.1016/j.chemosphere.2014.04.092}, abstractNote={Development of methods for assessing exposure and effects of waterborne toxicants on stream invertebrate species is important to elucidate environmentally relevant information. Current protocols for freshwater invertebrate toxicity testing almost exclusively utilize cladocerans, amphipods or chironomids rather than the more typical aquatic insect taxa found in lotic systems. Centroptilum triangulifer is a parthenogenetic mayfly occurring in depositional habitats of streams and rivers of the Eastern U.S. and Canada. C. triangulifer is an ideal stream insect for toxicity testing under field and laboratory conditions because of its short life cycle, parthenogenetic mode of reproduction, and it represents a group considered sensitive to environmental stressors. In this study, a colony of C. triangulifer was reared using a defined diet of three diatoms, Mayamaea atomus var. permitis, Nitzschia cf. pusilla, and Achnanthidium minutissimum. Percent survival (⩾80%), fecundity measurements (⩾1000 eggs) and pre-egg laying weights were used as indicators of overall colony health and fitness in our laboratory water (Lab-line) and in Moderately Hard Reconstituted Water (MHRW). Lab-line reared C. triangulifer had average survival rate of 92.69% for eleven generations and 82.99% over thirteen generations. MHRW reared C. triangulifer had an average survival rate of 80.65% for four generations and three generations of fecundities greater than 1000 eggs per individual. Pre-egg laying weight and fecundity were highly correlated and a best-fit model equation was derived to estimate egg counts for future generations. Establishment of this culturing protocol provides a more ecologically relevant species for toxicity testing and aids in further stressor identification for stream bioassessments.}, journal={CHEMOSPHERE}, author={Weaver, Paul C. and Lazorchak, James M. and Struewing, Katherine A. and DeCelles, Susanna J. and Funk, David H. and Buchwalter, David B. and Johnson, Brent R.}, year={2015}, month={Nov}, pages={589–596} }
 @article{struewing_lazorchak_weaver_johnson_funk_buchwalter_2015, title={Part 2: Sensitivity comparisons of the mayfly Centroptilum triangulifer to Ceriodaphnia dubia and Daphnia magna using standard reference toxicants; NaCl, KCl and CuSO4}, volume={139}, ISSN={["1879-1298"]}, DOI={10.1016/j.chemosphere.2014.04.096}, abstractNote={Criteria for establishing water quality standards that are protective for 95% of the native species are generally based upon laboratory toxicity tests. These tests utilize common model organisms that have established test methods. However, for invertebrates these species represent mostly the zooplankton community and are not inclusive of all taxa. In order to examine a potential under-representation in emerging aquatic invertebrates the US Environmental Protection Agency has cultured a parthenogenetic mayfly, Centroptilum triangulifer (Ephemeroptera: Baetidae). This study established a 48 h acute and a 14-day short-term chronic testing procedure for C. triangulifer and compared its sensitivity to two model invertebrates, Ceriodaphnia dubia and Daphnia magna. Toxicity tests were conducted to determine mortality and growth effects using standard reference toxicants: NaCl, KCl and CuSO4. In 48-h acute tests, the average LC50 for the mayfly was 659 mg L−1 NaCl, 1957 mg L−1 KCl, and 11 μg L−1 CuSO4. IC25 values, using dry weight as the endpoint, were 228 mg L−1 NaCl, 356 mg L−1 KCl and 5 μg L−1 CuSO4. C. triangulifer was the most sensitive species in NaCl acute and chronic growth tests. At KCl concentrations tested, C. triangulifer was less sensitive for acute tests but was equally or more sensitive than C. dubia and D. magna for growth measurements. This study determined C. triangulifer has great potential and benefits for use in ecotoxicological studies.}, journal={CHEMOSPHERE}, author={Struewing, Katherine A. and Lazorchak, James M. and Weaver, Paul C. and Johnson, Brent R. and Funk, David H. and Buchwalter, David B.}, year={2015}, month={Nov}, pages={597–603} }
 @article{poteat_jacobus_buchwalter_2015, title={The importance of retaining a phylogenetic perspective in traits-based community analyses}, volume={60}, ISSN={["1365-2427"]}, DOI={10.1111/fwb.12571}, abstractNote={Summary}, number={7}, journal={FRESHWATER BIOLOGY}, author={Poteat, Monica D. and Jacobus, Luke M. and Buchwalter, David B.}, year={2015}, month={Jul}, pages={1330–1339} }
 @article{camp_funk_buchwalter_2014, title={A stressful shortness of breath: molting disrupts breathing in the mayfly Cloeon dipterum}, volume={33}, ISSN={["2161-9565"]}, DOI={10.1086/677899}, abstractNote={Abstract: Molting is a stressful event in insect development. When an insect molts, the individual discards its exoskeleton and sheds and renews the interior lining of substantial portions of the respiratory (tracheal) system. We profiled for the first time the disruptive pattern of respiration during the molting process in larvae of the mayfly Cloeon dipterum (Ephemeroptera:Baetidae). Molting induces a precipitous drop in O2 consumption immediately followed by a surge in O2 consumption that appears to be compensatory in nature. Postmolt metabolic suppression is consistently observed during which O2 consumption rates lag relative to those of nonmolting larvae. Furthermore, the magnitude of respiratory disturbance during the molt increases as a function of temperature. Increasing temperatures increase molting frequency and the apparently stressful nature of the molt itself. Thus, the insect molt appears to be a previously unappreciated route by which warming conditions may affect aquatic insects.}, number={3}, journal={FRESHWATER SCIENCE}, author={Camp, A. A. and Funk, D. H. and Buchwalter, D. B.}, year={2014}, month={Sep}, pages={695–699} }
 @article{poteat_buchwalter_2014, title={Calcium uptake in aquatic insects: influences of phylogeny and metals (Cd and Zn)}, volume={217}, ISSN={["1477-9145"]}, DOI={10.1242/jeb.097261}, abstractNote={Summary}, number={7}, journal={JOURNAL OF EXPERIMENTAL BIOLOGY}, author={Poteat, Monica D. and Buchwalter, David B.}, year={2014}, month={Apr}, pages={1180–1186} }
 @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{poteat_buchwalter_2014, title={Four Reasons Why Traditional Metal Toxicity Testing with Aquatic Insects Is Irrelevant}, volume={48}, ISSN={["1520-5851"]}, DOI={10.1021/es405529n}, abstractNote={T metal contamination of freshwater ecosystems is a problem worldwide, and insects are typically the predominant invertebrate faunal group in these systems. Metals can shape community structure, as evidenced by reduced biodiversity in affected areas. Aquatic insects are often some of the first species to disappear from metal-contaminated sites, despite the fact that laboratory toxicity tests would suggest that aquatic insects are generally insensitive to metals. In fact, typical laboratory results would indicate that insects only respond to dissolved metals at concentrations orders of magnitude larger than those found in the most insect-depleted contaminated sites. Even with mounting evidence highlighting the obvious disconnect between laboratory toxicity tests and field observations regarding metal toxicity to aquatic insects, water quality criteria for metals continues to rely primarily on toxicity values derived from short term dissolved-only exposures. Below we discuss four key reasons as to why such tests don’t provide relevant data for this important faunal group, focusing upon recent advances in our understanding of bioaccumulation and mechanisms of toxicity.}, number={2}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Poteat, Monica D. and Buchwalter, David B.}, year={2014}, month={Jan}, pages={887–888} }
 @article{keller_xie_buchwalter_franzreb_simons_2014, title={Mercury bioaccumulation in Southern Appalachian birds, assessed through feather concentrations}, volume={23}, ISSN={0963-9292 1573-3017}, url={http://dx.doi.org/10.1007/S10646-013-1174-6}, DOI={10.1007/S10646-013-1174-6}, abstractNote={Mercury contamination in wildlife has rarely been studied in the Southern Appalachians despite high deposition rates in the region. From 2006 to 2008 we sampled feathers from 458 birds representing 32 species in the Southern Appalachians for total mercury and stable isotope δ (15)N. Mercury concentrations (mean ± SE) averaged 0.46 ± 0.02 μg g(-1) (range 0.01-3.74 μg g(-1)). Twelve of 32 species had individuals (7 % of all birds sampled) with mercury concentrations higher than 1 μg g(-1). Mercury concentrations were 17 % higher in juveniles compared to adults (n = 454). In adults, invertivores has higher mercury levels compared to omnivores. Mercury was highest at low-elevation sites near water, however mercury was detected in all birds, including those in the high elevations (1,000-2,000 m). Relative trophic position, calculated from δ (15)N, ranged from 2.13 to 4.87 across all birds. We fitted linear mixed-effects models to the data separately for juveniles and year-round resident adults. In adults, mercury concentrations were 2.4 times higher in invertivores compared to omnivores. Trophic position was the main effect explaining mercury levels in juveniles, with an estimated 0.18 ± 0.08 μg g(-1) increase in feather mercury for each one unit rise in trophic position. Our research demonstrates that mercury is biomagnifying in birds within this terrestrial mountainous system, and further research is warranted for animals foraging at higher trophic levels, particularly those associated with aquatic environments downslope from montane areas receiving high mercury deposition.}, number={2}, journal={Ecotoxicology}, publisher={Springer Science and Business Media LLC}, author={Keller, Rebecca Hylton and Xie, Lingtian and Buchwalter, David B. and Franzreb, Kathleen E. and Simons, Theodore R.}, year={2014}, month={Jan}, pages={304–316} }
 @article{poteat_buchwalter_2014, title={Phylogeny and Size Differentially Influence Dissolved Cd and Zn Bioaccumulation Parameters among Closely Related Aquatic Insects}, volume={48}, ISSN={["1520-5851"]}, DOI={10.1021/es501096a}, abstractNote={Evolutionarily distinct lineages can vary markedly in their accumulation of, and sensitivity to, contaminants. However, less is known about variability among closely related species. Here, we compared dissolved Cd and Zn bioaccumulation in 19 species spanning two species-rich aquatic insect families: Ephemerellidae (order Ephemeroptera (mayflies)), generalized to be metal sensitive, and Hydropsychidae (order Trichoptera (caddisflies)), generalized to be metal tolerant. Across all species, Zn and Cd uptake rate constants (k(u)s), efflux rate constants (k(e)s) and bioconcentration factors (BCFs) strongly covaried, suggesting that these metals share transport pathways in these distinct lineages. K(u)s and BCFs were substantially larger in Ephemerellidae than in Hydropsychidae, whereas k(e)s did not dramatically differ between the two families. Body size played an important role in driving ku differences among species, but had no influence on k(e)s. While familial differences in metal bioconcentration were striking, each family exhibited tremendous variability in all bioaccumulation parameters. At finer levels of taxonomic resolution (within families), phylogeny did not account for differences in metal bioaccumulation. These findings suggest that intrafamily variability can be profound and have important practical implications in that we need to better understand how well "surrogate species" represent their fellow congeners and family members.}, number={9}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Poteat, Monica D. and Buchwalter, David B.}, year={2014}, month={May}, pages={5274–5281} }
 @article{díaz-jaramillo_da rocha_chiang_buchwalter_monserrat_barra_2013, title={Biochemical and behavioral responses in the estuarine polychaete Perinereis gualpensis (Nereididae) after in situ exposure to polluted sediments}, volume={89}, ISSN={0147-6513}, url={http://dx.doi.org/10.1016/j.ecoenv.2012.11.026}, DOI={10.1016/j.ecoenv.2012.11.026}, abstractNote={In situ translocation experiments are advantageous relative to traditional laboratory experiments, particularly for understanding the bioavailability of trace metals like mercury (Hg). Individuals of the polychaete Perinereis gualpensis were translocated from a reference site (Raqui estuary, Chile) to an estuarine site with significant sediment Hg concentrations (Lenga estuary: 1.78–9.89 mg/kg). Individuals were exposed in polluted and non-polluted sediments for 21 days and sampled every 7 days with cages deployed at three different depths. Tissue Hg concentrations were measured in conjunction with oxidative stress responses. Translocated polychaetes rapidly accumulated Hg. Glutathione S-transferase (GST) activities measured from posterior body regions were 2-fold higher than control activities after 21 days of exposure. Other antioxidant measures were idiosyncratic. Distinct burrowing behavior differences were observed; control polychaetes exhibited more homogenous vertical distributions, whereas in Lenga, worms tended to remain in upper layers. These studies demonstrate that under natural conditions, Hg is highly bioavailable to polychaetes affecting both biochemical and behavioral responses after relatively short-term exposure.}, journal={Ecotoxicology and Environmental Safety}, publisher={Elsevier BV}, author={Díaz-Jaramillo, Mauricio and da Rocha, Alessandra Martins and Chiang, Gustavo and Buchwalter, David and Monserrat, José M. and Barra, Ricardo}, year={2013}, month={Mar}, pages={182–188} }
 @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{poteat_garland_fisher_wang_buchwalter_2013, title={Evolutionary Patterns in Trace Metal (Cd and Zn) Efflux Capacity in Aquatic Organisms}, volume={47}, ISSN={["1520-5851"]}, DOI={10.1021/es401368u}, abstractNote={The ability to eliminate (efflux) metals is a physiological trait that acts as a major driver of bioaccumulation differences among species. This species-specific trait plays a large role in determining the metal loads that species will need to detoxify to persist in chronically contaminated environments and, therefore, contributes significantly to differences in environmental sensitivity among species. To develop a better understanding of how efflux varies within and among taxonomic groupings, we compared Cd and Zn efflux rate constants (ke values) among members of two species-rich aquatic insect families, Ephemerellidae and Hydropsychidae, and discovered that ke values strongly covaried across species. This relationship allowed us to successfully predict Zn efflux from Cd data gathered from aquatic species belonging to other insect orders and families. We then performed a broader, comparative analysis of Cd and Zn ke values from existing data for arthropods, mollusks, annelids, and chordates (77 species total) and found significant phylogenetic patterns. Taxonomic groups exhibited marked variability in ke magnitudes and ranges, suggesting that some groups are more constrained than others in their abilities to eliminate metals. Understanding broader patterns of variability can lead to more rational extrapolations across species and improved protectiveness in water-quality criteria and ecological assessment.}, number={14}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Poteat, Monica D. and Garland, Theodore, Jr. and Fisher, Nicholas S. and Wang, Wen-Xiong and Buchwalter, David B.}, year={2013}, month={Jul}, pages={7989–7995} }
 @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{kim_funk_buchwalter_2012, title={Dietary (periphyton) and aqueous Zn bioaccumulation dynamics in the mayfly Centroptilum triangulifer}, volume={21}, ISSN={["0963-9292"]}, DOI={10.1007/s10646-012-0985-1}, abstractNote={Diet is often the predominant route of trace metal exposure in aquatic insects. In freshwater ecosystems, periphyton serves as a primary source of food to many aquatic insects and is a major sink for trace metals. We investigated the bioconcentration of the essential metal Zn by periphyton using (65)Zn as a radiotracer. At relatively low dissolved concentrations (2-20 μg L(-1)), non steady state Zn bioconcentration by periphyton averaged 6,099 ± 2,430-fold, with much of the variability determined by loading regime (number of renewals and duration of exposures). Labeled periphyton was used as a food source for dietary accumulation studies with the mayfly Centroptilum triangulifer. After 29 days, larvae concentrated Zn 19-, 16- and 17-fold relative to dietary Zn concentrations of 8.1, 43.2 and 82.3 μg g(-1) (dry weight), respectively. Adults from that same cohort only concentrated Zn 8-, 3- and 3- fold relative to those same dietary concentrations, revealing that mayflies lose significant Zn prior to reaching adulthood. Anecdotal evidence suggests that this loss occurs prior to emergence to the subimago, as negligible Zn was found in the subimago to imago exuvium. Across a range of adult tissue concentrations, maternal transfer consistently averaged 26.7 %. Uptake (k(u), 0.26 L g(-1 )d(-1)) and efflux rate constants (k(e), 0.001-0.007 d(-1)) were measured and assimilation efficiencies from dietary Zn concentrations of 4.9 and 59.7 μg Zn g(-1) were estimated to be 88 ± 4 % and 64 ± 15 %, respectively. Both life cycle and biodynamic modeling approaches point towards diet being the primary route of Zn bioaccumulation in this mayfly.}, number={8}, journal={ECOTOXICOLOGY}, author={Kim, K. S. and Funk, D. H. and Buchwalter, D. B.}, year={2012}, month={Nov}, pages={2288–2296} }
 @article{poteat_diaz-jaramillo_buchwalter_2012, title={Divalent metal (Ca, Cd, Mn, Zn) uptake and interactions in the aquatic insect Hydropsyche sparna}, volume={215}, ISSN={["1477-9145"]}, DOI={10.1242/jeb.063412}, abstractNote={SUMMARY}, number={9}, journal={JOURNAL OF EXPERIMENTAL BIOLOGY}, author={Poteat, Monica D. and Diaz-Jaramillo, Mauricio and Buchwalter, David B.}, year={2012}, month={May}, pages={1575–1583} }
 @article{shuford_poteat_buchwalter_muddiman_2011, title={Absolute quantification of free glutathione and cysteine in aquatic insects using isotope dilution and selected reaction monitoring}, volume={402}, ISSN={1618-2642 1618-2650}, url={http://dx.doi.org/10.1007/S00216-011-5416-2}, DOI={10.1007/S00216-011-5416-2}, abstractNote={A simple and robust isotope dilution mass spectrometry-based assay was developed for the determination of free cysteine and glutathione (GSH) in aquatic insects. Several experimental parameters were evaluated and optimized to provide specific and sensitive detection of both compounds by in situ derivatization with N-ethylmaleimide followed by acid alkylation quenching and reverse-phased liquid chromatography coupled with selected reaction monitoring. For both targets, the assay was evaluated over a concentration range of 0.313 to 320 μM and was demonstrated to have a quantitative dynamic range spanning nearly three orders of magnitude, with lower limits of quantification being 0.330 μM for GSH and 0.370 μM for cysteine. Additionally, measurements were observed to be highly reproducible over the course of several days. When applied to the analysis of four different species of insects, large biological variation between and within species was observed. Different feeding regimens were also tested within two species of insects but statistical comparisons revealed no significant difference in the levels of either compound.}, number={1}, journal={Analytical and Bioanalytical Chemistry}, publisher={Springer Science and Business Media LLC}, author={Shuford, Christopher M. and Poteat, Monica D. and Buchwalter, David B. and Muddiman, David C.}, year={2011}, month={Sep}, pages={357–366} }
 @article{xie_buchwalter_2011, title={Cadmium exposure route affects antioxidant responses in the mayfly Centroptilum triangulifer}, volume={105}, ISSN={["1879-1514"]}, DOI={10.1016/j.aquatox.2011.06.009}, abstractNote={Aquatic organisms accumulate metals directly from water and from their diets. Exposure to metals is known to generate oxidative stress in living organisms and this stress may be ameliorated via activation of antioxidant enzymes and non-enzymatic antioxidants. To determine if antioxidant physiology is dependent on Cd exposure route in the mayfly Centroptilum triangulifer, we exposed larvae to environmentally relevant concentrations of Cd from isolated dissolved or dietary exposure routes to achieve comparable tissue concentrations. Dissolved Cd had no effect on the antioxidant enzymes examined. However, dietary Cd significantly suppressed catalase and superoxide dismutase activities, and decreased concentrations of the reduced (active) form of glutathione in C. triangulifer larvae. These findings suggest that dietary Cd is potentially more toxic than aqueously derived Cd in this mayfly. We further examined the effect of dietary Cd tissue loading rates on antioxidant enzyme suppression and found that absolute tissue load appeared more important than loading rate. These results may help explain why insects are routinely unresponsive to dissolved metal exposures in the laboratory, yet highly responsive to metal pollution in nature.}, number={3-4}, journal={AQUATIC TOXICOLOGY}, author={Xie, Lingtian and Buchwalter, David B.}, year={2011}, month={Oct}, pages={199–205} }
 @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} }
 @article{kurochkin_etzkorn_buchwalter_leamy_sokolova_2011, title={Top-down control analysis of the cadmium effects on molluscan mitochondria and the mechanisms of cadmium-induced mitochondrial dysfunction}, volume={300}, ISSN={["0363-6119"]}, DOI={10.1152/ajpregu.00279.2010}, abstractNote={Cadmium (Cd) is a toxic metal and an important environmental pollutant that can strongly affect mitochondrial function and bioenergetics in animals. We investigated the mechanisms of Cd action on mitochondrial function of a marine mollusk (the eastern oyster Crassostrea virginica ) by performing a top-down control analysis of the three major mitochondrial subsystems (substrate oxidation, proton leak, and phosphorylation). Our results showed that the substrate oxidation and proton leak subsystems are the main targets for Cd toxicity in oyster mitochondria. Exposure to 12.5 μM Cd strongly inhibited the substrate oxidation subsystem and stimulated the proton conductance across the inner mitochondrial membrane. Proton conductance was also elevated and substrate oxidation inhibited by Cd in the presence of a mitochondrially targeted antioxidant, MitoVitE, indicating that Cd effects on these subsystems were to a large extent ROS independent. Cd did not affect the kinetics of the phosphorylation system, indicating that it has negligible effects on F1, FOATP synthase and/or the adenine nucleotide transporter in oyster mitochondria. Cd exposure altered the patterns of control over mitochondrial respiration, increasing the degree of control conferred by the substrate oxidation subsystem, especially in resting (state 4) mitochondria. Taken together, these data suggest that Cd-induced decrease of mitochondrial efficiency and ATP production are predominantly driven by the high sensitivity of substrate oxidation and proton leak subsystems to this metal.}, number={1}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY}, author={Kurochkin, Ilya O. and Etzkorn, Markus and Buchwalter, David and Leamy, Larry and Sokolova, Inna M.}, year={2011}, month={Jan}, pages={R21–R31} }
 @article{sackett_aday_rice_cope_buchwalter_2010, title={Does proximity to coal-fired power plants influence fish tissue mercury?}, volume={19}, ISSN={["1573-3017"]}, DOI={10.1007/s10646-010-0545-5}, abstractNote={Much of the mercury contamination in aquatic biota originates from coal-fired power plants, point sources that release mercury into the atmosphere. Understanding mercury dynamics is primarily important because of the toxic threat mercury poses to wildlife and humans through the consumption of contaminated fish. In this study, we quantified the relative importance of proximity to coal-fired power plants on mercury accumulation in two fish species of different trophic positions. Fish, water and sediment were collected and analyzed from 14 lakes, seven near to (<10 km) and seven far from (>30 km) coal-fired power plants. Lower tissue mercury and higher tissue selenium concentrations were measured in fish collected near power plants. Moreover, mercury accumulation in fish was driven by biotic characteristics (e.g., trophic position, total length, age), waterbody characteristics (e.g., pH, dissolved organic carbon and sulfate) and distance from power plants. Proximity to an atmospheric point-source of mercury and selenium, such as a coal-fired power plant, affects the quantities of mercury and selenium accumulated in fish tissue. Differences in accumulation are hypothesized to be driven in part by selenium-mitigated reductions in fish tissue mercury near power plants. Although reduced fish tissue mercury in systems near power plants may decrease mercury-specific risks to human consumers, these benefits are highly localized and the relatively high selenium associated with these tissues may compromise ecological health.}, number={8}, journal={ECOTOXICOLOGY}, author={Sackett, Dana K. and Aday, D. Derek and Rice, James A. and Cope, W. Gregory and Buchwalter, David}, year={2010}, month={Nov}, pages={1601–1611} }
 @article{rubach_ashauer_buchwalter_de lange_hamer_preuss_töpke_maund_2010, title={Framework for traits-based assessment in ecotoxicology}, volume={7}, ISSN={1551-3777}, url={http://dx.doi.org/10.1002/ieam.105}, DOI={10.1002/ieam.105}, abstractNote={Abstract}, number={2}, journal={Integrated Environmental Assessment and Management}, publisher={Wiley}, author={Rubach, Mascha N and Ashauer, Roman and Buchwalter, David B and De Lange, HJ and Hamer, Mick and Preuss, Thomas G and Töpke, Katrien and Maund, Stephen J}, year={2010}, month={Jul}, pages={172–186} }
 @article{dittman_buchwalter_2010, title={Manganese Bioconcentration in Aquatic Insects: Mn Oxide Coatings, Molting Loss, and Mn(II) Thiol Scavenging}, volume={44}, ISSN={["1520-5851"]}, DOI={10.1021/es1022043}, abstractNote={Streams below mountaintop removal-valley fill coal mining operations often have elevated Mn concentrations, but it remains unclear if Mn plays a role in biodiversity reduction. We examined various aspects of aqueous Mn interactions with aquatic insects exposed to environmentally relevant Mn concentrations, revealing complex behavior. First, Mn accumulation rates varied widely among 9 species. A significant percentage of total Mn accrued (mean 74%, range 24-95%) was associated with the cuticle, predominantly in the form of Mn-oxides, and to a lesser degree Mn(II). Mn II is also absorbed into tissues, possibly through calcium transporters. Increased ambient calcium concentrations decreased both adsorbed and absorbed Mn accumulation from solution. Though species showed similar Mn efflux rate constants (0.032-0.072 d(-1)), the primary mode of Mn loss was through molting. Both adsorbed and absorbed Mn is lost during the molt. Subcellular compartmentalization studies revealed an overwhelming tendency for internalized Mn to associate with the heat stable cytosolic protein fraction. After short dissolved Mn exposures, intracellular glutathione and cysteine levels were markedly reduced relative to controls. These findings suggest that Mn exposure results in transient physiological stress in aquatic insects which is likely relieved, in part, during the molting process.}, number={23}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Dittman, Elizabeth K. and Buchwalter, David B.}, year={2010}, month={Dec}, pages={9182–9188} }
 @article{xie_funk_buchwalter_2010, title={Trophic transfer of Cd from natural periphyton to the grazing mayfly Centroptilum triangulifer in a life cycle test}, volume={158}, ISSN={["1873-6424"]}, DOI={10.1016/j.envpol.2009.07.010}, abstractNote={In streams, periphyton biofilms are important sinks for trace metals such as cadmium and are primary food sources of many invertebrate consumers. To study Cd trophic transfer, we produced differentially contaminated diets by exposing natural periphyton to environmentally relevant dissolved Cd ranging from 0 to 10 μg L−1 for 6–7 days using a radiotracer approach. On average, periphyton grown during three different seasons bioconcentrated Cd similarly – approximately 1315 (±442) -fold above dissolved concentrations. However, mayfly larvae (Centroptilum triangulifer) raised on these differentially contaminated diets (first instar through adulthood) had significantly higher trophic transfer factors from periphyton grown in Aug and Nov 2008 (4.30 ± 1.55) than from periphyton grown in Jan 2009 (0.85 ± 0.21). This Cd bioaccumulation difference is only partially explained by apparent food quality and subsequent growth differences. Taken together, these results suggest that primary producers at the base of food webs drive metal bioaccumulation by invertebrate grazers.}, number={1}, journal={ENVIRONMENTAL POLLUTION}, author={Xie, Lingtian and Funk, David H. and Buchwalter, David B.}, year={2010}, month={Jan}, pages={272–277} }
 @article{xie_flippin_deighton_funk_dickey_buchwalter_2009, title={Mercury(II) Bioaccumulation and Antioxidant Physiology in Four Aquatic Insects}, volume={43}, ISSN={["1520-5851"]}, DOI={10.1021/es802323r}, abstractNote={We examined Hg(II) bioaccumulation and compartmentalization patterns in conjunction with antioxidant responses in four aquatic insect species: two caddisflies (Chimarra sp. and Hydropsyche betteni) and two mayflies (Maccaffertium modestum and Isonychia sp). Total antioxidant capabilities differed among unexposed larvae, with both caddisfly species exhibiting elevated antioxidant activities relative to the mayflies. We were able to account for these differences by examining the constitutive activities of catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), and superoxide dismutase (SOD), in the four species. We also examined levels of reduced and oxidized glutathione and cysteine in the insects. Glutathione peroxidase and SOD were the most responsive to Hg exposure, with GPx catalytic activity increasing between 50 and 310%. Superoxide dismutase activity decreased between 35 and 50%. This SOD suppression was shown to be dose-dependent in both caddisflies, butthe strength of this suppression did not appear to be related to rates of uptake. Surprisingly, little Hg (<10%) was found in the heat-stable cytosolic protein subcellular compartment in each of the four species, suggesting that Hg was not well detoxified. By combining bioaccumulation studies with other physiological measures, we can begin to better understand the consequences of trace metal pollutants in nature.}, number={3}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Xie, Lingtian and Flippin, Jennifer L. and Deighton, Nigel and Funk, David H. and Dickey, David A. and Buchwalter, David B.}, year={2009}, month={Feb}, pages={934–940} }
 @article{conley_funk_buchwalter_2009, title={Selenium Bioaccumulation and Maternal Transfer in the Mayfly Centroptilum triangulifer in a Life-Cycle, Periphyton-Biofilm Trophic Assay}, volume={43}, ISSN={["0013-936X"]}, DOI={10.1021/es9016377}, abstractNote={Selenium contamination in aquatic ecosystems provides management challenges because bioaccumulation in animals is largely a function of dietary exposure, whereas regulatory entities have traditionally focused on direct water to organism interactions. Selenium is known to be readily absorbed by primary producers and can potentially biomagnify in food webs and elicit adverse effects in higher trophic levels. However, selenium bioaccumulation in the invertebrate prey of many predatory animals is poorly understood. Here, we used 75Se (as selenite) as a radiotracer to characterize Se bioaccumulation into natural periphyton biofilms and subsequent dietary and maternal transfer in the mayfly, Centroptilum triangulifer, in a life-cycle assay. On average periphyton biofilms bioconcentrated selenium 1113 (+/-430)-fold following 7-9 days of exposure to a range of environmentally relevant dissolved concentrations (2.4-13.9 microg L(-1)). Mayflies grown to adulthood on these diets further biomagnified Se with trophic transfer factors averaging 22 (+/-0.4)-fold in postpartum maternal tissues. Adults then transferred 46.5 (+/-8.8)% of their body burdens to eggs with an observed reduction in fecundity for mayflies fed on diets greater than approximately 11 microg g(-1). These results suggest that at environmentally feasible dietary Se concentrations insects are potentially affected by Se exposure, and that the current presumption that insects are simply conduits of Se to higher trophic levels is inaccurate.}, number={20}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Conley, Justin M. and Funk, David H. and Buchwalter, David B.}, year={2009}, month={Oct}, pages={7952–7957} }
 @article{buchwalter_cain_martin_xie_luoma_garland_2008, title={Aquatic insect ecophysiological traits reveal phylogenetically based differences in dissolved cadmium susceptibility}, volume={105}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.0801686105}, abstractNote={We used a phylogenetically based comparative approach to evaluate the potential for physiological studies to reveal patterns of diversity in traits related to susceptibility to an environmental stressor, the trace metal cadmium (Cd). Physiological traits related to Cd bioaccumulation, compartmentalization, and ultimately susceptibility were measured in 21 aquatic insect species representing the orders Ephemeroptera, Plecoptera, and Trichoptera. We mapped these experimentally derived physiological traits onto a phylogeny and quantified the tendency for related species to be similar (phylogenetic signal). All traits related to Cd bioaccumulation and susceptibility exhibited statistically significant phylogenetic signal, although the signal strength varied among traits. Conventional and phylogenetically based regression models were compared, revealing great variability within orders but consistent, strong differences among insect families. Uptake and elimination rate constants were positively correlated among species, but only when effects of body size and phylogeny were incorporated in the analysis. Together, uptake and elimination rates predicted dramatic Cd bioaccumulation differences among species that agreed with field-based measurements. We discovered a potential tradeoff between the ability to eliminate Cd and the ability to detoxify it across species, particularly mayflies. The best-fit regression models were driven by phylogenetic parameters (especially differences among families) rather than functional traits, suggesting that it may eventually be possible to predict a taxon's physiological performance based on its phylogenetic position, provided adequate physiological information is available for close relatives. There appears to be great potential for evolutionary physiological approaches to augment our understanding of insect responses to environmental stressors in nature.}, number={24}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Buchwalter, David B. and Cain, Daniel J. and Martin, Caitrin A. and Xie, Lingtian and Luoma, Samuel N. and Garland, Theodore, Jr.}, year={2008}, month={Jun}, pages={8321–8326} }
 @article{xie_lambert_martin_cain_luoma_buchwalter_2008, title={Cadmium biodynamics in the oligochaete Lumbriculus variegatus and its implications for trophic transfer}, volume={86}, ISSN={["0166-445X"]}, DOI={10.1016/j.aquatox.2007.11.008}, abstractNote={It has become increasingly apparent that diet can be a major source of trace metal bioaccumulation in aquatic organisms. In this study, we examined cadmium uptake, efflux, and subcellular compartmentalization dynamics in the freshwater oligochaete Lumbriculus variegatus. L. variegatus is an important component of freshwater food webs in Europe and North America and is potentially useful as a standard food source for laboratory-based trophic transfer studies. Cadmium accumulation and depuration were each followed for 10 days. Rate constants of uptake (ku) and efflux (ke) were estimated and subcellular Cd compartmentalization was followed over the course of uptake and efflux. The partitioning of Cd into operationally-defined subcellular compartments was relatively consistent throughout the 20-day experiment, with the majority of Cd accumulating in the cytosol. No major changes in Cd compartmentalization were observed over uptake or depuration, but there appeared to be some exchange between heat-stable and heat-labile cytosolic protein fractions. Cadmium accumulation from solution was strongly affected by ambient calcium concentrations, suggesting competition between Cd and Ca for uptake sites. Finally, we demonstrate the ability to manipulate the whole body calcium content of L. variegatus as a potential tool for examining calcium influences on dietary Cd dynamics. The potential for this species to be an important conduit of Cd to higher trophic levels is discussed, along with its potential as a standardized food source in metal trophic transfer studies.}, number={2}, journal={AQUATIC TOXICOLOGY}, author={Xie, Lingtian and Lambert, Daniel and Martin, Caitrin and Cain, Daniel J. and Luoma, Samuel N. and Buchwalter, David}, year={2008}, month={Jan}, pages={265–271} }
 @article{cope_bringolf_buchwalter_newton_ingersoll_wang_augspurger_dwyer_barnhart_neves_et al._2008, title={Differential exposure, duration, and sensitivity of unionoidean bivalve life stages to environmental contaminants}, volume={27}, ISSN={["0887-3593"]}, DOI={10.1899/07-094.1}, abstractNote={Abstract Freshwater mussels (superfamily Unionoidea) are in serious global decline and in urgent need of protection and conservation. The declines have been attributed to a wide array of human activities resulting in pollution and water-quality degradation, and habitat destruction and alteration. Linkages among poor water quality, pollutant sources, and mussel decline in rivers and streams have been associated with results of laboratory-based tests of specific pollutants. However, uncertainties remain about the relationship of laboratory data to actual contaminant exposure routes for various mussel species, life stages, and in the habitats occupied during these exposures. We evaluated the pathways of exposure to environmental pollutants for all 4 life stages (free glochidia, encysted glochidia, juveniles, adults) of unionoidean mussels and found that each life stage has both common and unique characteristics that contribute to observed differences in exposure and sensitivity. Free glochidia typically are exposed only briefly (e.g., seconds to days) through surface water, whereas adults sustain exposure over years to decades through surface water, pore water, sediment, and diet. Juveniles live largely burrowed in the sediment for the first 0 to 4 y of life. Thus, sediment, pore water, and diet are the predominant exposure routes for this life stage, but surface water also might contribute to exposure during certain periods and environmental conditions. The obligate parasitic stage (encysted glochidia stage) on a host fish might be exposed from surface water while partially encysted or from toxicants in host-fish tissue while fully encysted. Laboratory methods for testing for acute and chronic exposures in water have advanced, and toxicant-specific information has increased in recent years. However, additional research is needed to understand interactions of life history, habitat, and long-term exposure to contaminants through water, pore water, sediment, and diet so that the risks of environmental exposures can be properly assessed and managed.}, number={2}, journal={JOURNAL OF THE NORTH AMERICAN BENTHOLOGICAL SOCIETY}, author={Cope, W. Gregory and Bringolf, Robert B. and Buchwalter, David B. and Newton, Teresa J. and Ingersoll, Christopher G. and Wang, Ning and Augspurger, Tom and Dwyer, F. James and Barnhart, M. Christopher and Neves, Richard J. and et al.}, year={2008}, month={Jun}, pages={451–462} }
 @article{buchwalter_cain_clements_luoma_2008, title={Using Biodynamic Models to Reconcile Differences between Laboratory Toxicity Tests and Field Biomonitoring with Aquatic Insects}, volume={42}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es703130e}, DOI={10.1021/es703130e}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTUsing Biodynamic Models to Reconcile Differences between Laboratory Toxicity Tests and Field Biomonitoring with Aquatic InsectsDavid B. Buchwalter*, Daniel J. Cain, William H. Clements, and Samuel N. LuomaCite this: Environ. Sci. Technol. 2008, 42, 8, 3117Publication Date (Web):March 15, 2008Publication History Accepted31 January 2008Published online15 March 2008Published inissue 1 April 2008https://doi.org/10.1021/es703130eCopyright © 2008 American Chemical SocietyRequest reuse permissions This publication is free to access through this site. Learn MoreArticle Views463Altmetric-Citations3LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (41 KB) Get e-AlertscloseSUBJECTS:Antibiotic resistance,Environmental pollution,Kinetic parameters,Toxicity Get e-Alerts}, number={8}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Buchwalter, David B. and Cain, Daniel J. and Clements, William H. and Luoma, Samuel N.}, year={2008}, month={Apr}, pages={3117–3117} }
 @article{martin_luoma_cain_buchwalter_2007, title={Cadmium Ecophysiology in Seven Stonefly (Plecoptera) Species:  Delineating Sources and Estimating Susceptibility}, volume={41}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es071205b}, DOI={10.1021/es071205b}, abstractNote={A major challenge in ecotoxicology lies in generating data under experimental conditions that are relevant to understanding contaminant effects in nature. Biodynamic modeling combines species-specific physiological traits to make predictions of metal bioaccumulation that fare well when tested in the field. We generated biodynamic models for seven predatory stonefly (Plecoptera) species representing the families Perlidae (5) and Perlodidae (2). Each taxon was exposed to cadmium independently via diet and via solution. Species varied approximately 2.6 fold in predicted steady-state cadmium concentrations. Diet was the predominant source of accumulated cadmium in five of the seven species and averaged 53.2 +/- 9.6% and 90.2 +/- 3.7% of net Cd accumulation in perlids and perlodids, respectively. Differences in Cd bioaccumulation between the two families were largely driven by differences in dissolved accumulation rates, which were considerably slower in perlodidsthan in perlids. We further examined the subcellular compartmentalization of Cd accumulated from independent aqueous and dietary exposures. Predicted steady-state concentrations were modified to only consider Cd accumulated in metal-sensitive subcellular compartments. These values ranged 5.3 fold. We discuss this variability within a phylogenetic context and its implications for bioassessment.}, number={20}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Martin, Caitrin A. and Luoma, Samuel N. and Cain, Daniel J. and Buchwalter, David B.}, year={2007}, month={Oct}, pages={7171–7177} }
 @article{martin_luoma_cain_buchwalter_2007, title={Cadmium ecophysiology in seven stonefly (Plecoptera) species: Delineating sources and estimating susceptibility}, volume={41}, DOI={10.1021/es0712051b}, number={20}, journal={Environmental Science & Technology}, author={Martin, C. A. and Luoma, S. N. and Cain, D. J. and Buchwalter, D. B.}, year={2007}, pages={7171–7177} }
 @article{buchwalter_cain_clements_lucima_2007, title={Using biodynammic models to reconcile differences between laboratory toxicity tests and field biomonitoring with aquatic insects}, volume={41}, ISSN={["1520-5851"]}, DOI={10.1021/es070464y}, abstractNote={Aquatic insects often dominate lotic ecosystems, yet these organisms are under-represented in trace metal toxicity databases. Furthermore, toxicity data for aquatic insects do not appear to reflect their actual sensitivities to metals in nature, because the concentrations required to elicit toxicity in the laboratory are considerably higher than those found to impact insect communities in the field. New approaches are therefore needed to better understand how and why insects are differentially susceptible to metal exposures. Biodynamic modeling is a powerful tool for understanding interspecific differences in trace metal bioaccumulation. Because bioaccumulation alone does not necessarily correlate with toxicity, we combined biokinetic parameters associated with dissolved cadmium exposures with studies of the subcellular compartmentalization of accumulated Cd. This combination of physiological traits allowed us to make predictions of susceptibility differences to dissolved Cd in three aquatic insect taxa: Ephemerella excrucians, Rhithrogena morrisoni, and Rhyacophila sp. We compared these predictions with long-term field monitoring data and toxicity tests with closely related taxa: Ephemerella infrequens, Rhithrogena hageni, and Rhyacophila brunea. Kinetic parameters allowed us to estimate steady-state concentrations, the time required to reach steady state, and the concentrations of Cd projected to be in potentially toxic compartments for different species. Species-specific physiological traits identified using biodynamic models provided a means for better understanding why toxicity assays with insects have failed to provide meaningful estimates for metal concentrations that would be expected to be protective in nature.}, number={13}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Buchwalter, D. B. and Cain, D. J. and Clements, W. H. and Lucima, S. N.}, year={2007}, month={Jul}, pages={4821–4828} }
 @article{buchwalter_luoma_2005, title={Differences in Dissolved Cadmium and Zinc Uptake among Stream Insects:  Mechanistic Explanations}, volume={39}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es0404421}, DOI={10.1021/es0404421}, abstractNote={This study examined the extent to which dissolved Cd and Zn uptake rates vary in several aquatic insect taxa commonly used as indicators of ecological health. We further attempted to explain the mechanisms underlying observed differences. By comparing dissolved Cd and Zn uptake rates in several aquatic insect species, we demonstrated that species vary widely in these processes. Dissolved uptake rates were not related to gross morphological features such as body size or gill size--features that influence water permeability and therefore have ionoregulatory importance. However, finer morphological features, specifically, the relative numbers of ionoregulatory cells (chloride cells), appeared to be related to dissolved metal uptake rates. This observation was supported by Michaelis-Menten type kinetics experiments, which showed that dissolved Cd uptake rates were driven by the numbers of Cd transporters and not by the affinities of those transporters to Cd. Calcium concentrations in exposure media similarly affected Cd and Zn uptake rates in the caddisfly Hydropsyche californica. Dissolved Cd and Zn uptake rates strongly co-varied among species, suggesting that these metals are transported by similar mechanisms.}, number={2}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Buchwalter, David B. and Luoma, Samuel N.}, year={2005}, month={Jan}, pages={498–504} }
 @article{buchwalter_sandahl_jenkins_curtis_2004, title={Roles of uptake, biotransformation, and target site sensitivity in determining the differential toxicity of chlorpyrifos to second to fourth instar Chironomous riparius (Meigen)}, volume={66}, ISSN={0166-445X}, url={http://dx.doi.org/10.1016/j.aquatox.2003.08.004}, DOI={10.1016/j.aquatox.2003.08.004}, abstractNote={Early life stages of aquatic organisms tend to be more sensitive to various chemical contaminants than later life stages. This research attempted to identify the key biological factors that determined sensitivity differences among life stages of the aquatic insect Chironomous riparius. Specifically, second to fourth instar larvae were exposed in vivo to both low and high waterborne concentrations of chlorpyrifos to examine differences in accumulation rates, chlorpyrifos biotransformation, and overall sensitivity among instars. In vitro acetylcholinesterase (AChE) assays were performed with chlorpyrifos and the metabolite, chlorpyrifos-oxon, to investigate potential target site sensitivity differences among instars. Earlier instars accumulated chlorpyrifos more rapidly than later instars. There were no major differences among instars in the biotransformation rates of chlorpyrifos to the more polar metabolites, chlorpyrifos-oxon, and chlorpyridinol (TCP). Homogenate AChE activities from second to fourth instar larvae were refractory to chlorpyrifos, even at high concentrations. In contrast, homogenate AChE activities were responsive in a dose-dependent manner to chlorpyrifos-oxon. In general, it appeared that chlorpyrifos sensitivity differences among second to fourth instar C. riparius were largely determined by differences in uptake rates. In terms of AChE depression, fourth instar homogenates were more sensitive to chlorpyrifos and chlorpyrifos-oxon than earlier instars. However, basal AChE activity in fourth instar larvae was significantly higher than basal AChE activity in second to third instar larvae, which could potentially offset the apparent increased sensitivity to the oxon.}, number={2}, journal={Aquatic Toxicology}, publisher={Elsevier BV}, author={Buchwalter, D.B. and Sandahl, J.F. and Jenkins, J.J. and Curtis, L.R.}, year={2004}, month={Feb}, pages={149–157} }