Bioaccumulation and speciation of selenium in fish and insects collected from a mountaintop removal coal mining-impacted stream in West Virginia

Relationships among tissues, biofluids, and otolith selenium concentrations in wild female burbot (Lota lota)

In the Lake Koocanusa-Kootenai River system (Montana, USA and British Columbia, Canada), selenium (Se) contamination has become an international concern and is suspected to contribute to the observed burbot (Lota lota) population collapse. Due to our limited ability to sample burbot in Lake Koocanusa for monitoring studies, we used a reference population to develop tools to model tissue Se disposition for a focal species in systems with elevated Se. Total Se concentrations in otoliths, biofluids (blood and endolymph), and tissues (muscle, liver, and ovary) from burbot in reference lakes in northwestern Ontario, Canada, were measured to document tissue-to-tissue Se relationships and evaluate the potential for otoliths to retrace Se exposure in fish. Among burbot tissue, Se concentrations were the highest in the ovary (mean ± SD = 4.55 ± 2.23 μg g-1 dry mass [dm]), followed by the liver (2.69 ± 1.96 μg g-1  dm) and muscle (1.87 ± 1.14 μg g-1  dm), and decreased with body size (p < 0.05). In otoliths, Se was detected at low levels (<1 μg g-1 ). Selenium concentrations in burbot samples were positively correlated among muscle, ovary, liver, and endolymph tissues, but not for the most recent annually averaged or lifetime-averaged Se concentrations in otoliths. We hypothesize that Se concentrations were too low in this study to establish links between otoliths and other fish tissues and to detect significant lifetime variation in individuals, and that further validation using archived otoliths from burbot exposed to elevated Se levels in Lake Koocanusa-Kootenai River is needed to reconstruct exposure histories. However, intercompartmental models proved valuable for estimating Se concentrations in burbot tissues only available by means of lethal sampling (i.e., ovary), although additional work should confirm whether the established models are reliable to predict concentrations in Se-impaired systems as tissue distributions are likely to differ with increasing Se levels. Integr Environ Assess Manag 2023;00:1-11. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Trace Elements and Consequent Ecological Risks in Mining-Influenced Streams of Appalachia

Appalachian (eastern USA) coal surface mines fracture geologic materials, causing release of both major ions and trace elements to water via accelerated weathering. When elevated above natural background, trace elements in streams may produce adverse effects on biota via direct exposure from water and sediment and via dietary exposure in food sources. Other studies have found elevated water concentrations of multiple trace elements in Appalachia's mining-influenced streams. Except for Se, trace-element concentrations in abiotic and biotic media of Appalachian mining-influenced streams are less well known. We analyzed environmental media of headwater streams receiving alkaline waters from Appalachian coal mines for eight trace elements (Al, As, Cd, Cu, Ni, Sr, V, and Zn) and assessed the potential consequent ecological risks. Streamwater, particulate media (sediment, biofilm, leaf detritus), and benthic macroinvertebrates (primary consumers, secondary consumers, crayfish) were sampled from six mining-influenced and three reference streams during low-flow conditions in two seasons. Dissolved Cu, Ni, and Sr were higher in mining-influenced streams than in reference streams; Ni, Sr, and Zn in fine sediments and Ni in macroinvertebrates were also elevated relative to reference-stream levels in samples from mining-influenced streams. Seasonal ratios of mining-influenced stream concentrations to maximum concentrations in reference streams also demonstrated mining-influenced increases for several elements in multiple media. In most media, concentrations of several elements including Ni were correlated positively. All water-column dissolved concentrations were below protective levels, but fine-sediment concentrations of Ni approached or exceeded threshold-effect concentrations in several streams. Further study is warranted for several elements (Cd, Ni, and Zn in biofilms, and V in macroinvertebrates) that approached or exceeded previously established dietary-risk levels. Environ Toxicol Chem 2023;42:2651-2665. © 2023 SETAC.

Ecosystem modification and network position impact insect-mediated contaminant fluxes from a mountaintop mining-impacted river network

Aquatic-terrestrial contaminant transport via emerging aquatic insects has been studied across contaminant classes and aquatic ecosystems, but few studies have quantified the magnitude of these insect-mediated contaminant fluxes, limiting our understanding of their drivers. Using a recent conceptual model, we identified watershed mining extent, settling ponds, and network position as potential drivers of selenium (Se) fluxes from a mountaintop coal mining-impacted river network. Mining extent drove insect Se concentration (p = 0.008, R² = 0.406), but ponding and network position were the principal drivers of Se flux through their impact on insect production. Se fluxes were 18 times higher from ponded, mined tributaries than from unponded ones and were comparable to fluxes from larger, productive mainstem sites. Thus, contaminant fluxes were highest in the river mainstem or below ponds, indicating that without considering controls on insect production, contaminant fluxes and their associated risks for predators like birds and bats can be misestimated.

The geochemistry and hydrology of coal waste rock dumps: A systematic global review

Coal has been a major global resource for at least the past 250 years. The major waste product of coal mining is waste rock, which is stored in dumps of various sizes. Although the adverse effects of coal waste rock dumps on ecosystems and human health are widely recognised, there is little information on their internal hydrological and geochemical processes in the peer-reviewed literature. Coal and conventional waste rock dumps share many similarities, but coal waste rock dumps differ in structure, organic matter content, and size, which can affect the timing and rate of aqueous chemical release. In this global systematic review, we identify limited links to climate setting and dump construction, and inconsistent reporting of sampling and monitoring approaches, as limitations to the generalisation of findings. Furthermore, sources of aqueous constituents of interest (COIs) are not routinely or adequately identified, which can lead to incorrect assumptions regarding COI availability and geochemical mobility. Water flow regimes within dumps are dominated by matrix and/or preferential flow, depending on dump texture; these flow mechanisms exert a primary control on patterns of aqueous COI release. The inability to successfully transfer COI release rates from laboratory or field scale trials to operational scale dumps is primarily due to limitations of testing methods and fundamental characteristics of scale. Prediction of future release rates is hampered by a lack of long-term studies that fully characterise geochemistry (e.g., source and COI production rates) as well as dump hydrology (e.g., water balance, water migration). Five critical elements to include in best practice investigations are climate setting, dump physical characteristics, geochemical processes, water regime, and environmental load over time, as aqueous release of COIs from coal waste rock dumps occurs over decades to centuries. Key considerations are identified for each of these elements to guide best practice.

Synchrotron-Based Imaging Reveals the Fate of Selenium in Striped Marsh Frog Tadpoles

Synchrotron-based X-ray fluorescence microscopy (XFM) coupled with X-ray absorption near-edge structure (XANES) imaging was used to study selenium (Se) biodistribution and speciation in Limnodynastes peronii tadpoles. Tadpoles were exposed to dissolved Se (30 μg/L) as selenite (Se^IV) or selenate (Se^VI) for 7 days followed by 3 days of depuration. High-resolution elemental maps revealed that Se partitioned primarily in the eyes (specifically the eye lens, iris, and retinal pigmented epithelium), digestive and excretory organs of Se^IV-exposed tadpoles. Speciation analysis confirmed that the majority of accumulated Se was converted to organo-Se. Multielement analyses provided new information on Se colocalization and its impact on trace element homeostasis. New insights into the fate of Se on a whole organism scale contribute to our understanding of the mechanisms and risks associated with Se pollution.

Impact of the Microbial Origin and Active Microenvironment on the Shape of Biogenic Elemental Selenium Nanomaterials

The shape of nanomaterials affects their colloidal properties, cellular uptake, and fate in the environment. The microbial origin and microenvironment can play a role in altering the shape of the nanomaterial. However, such studies have never been conducted. Here, we demonstrate that the selenium nanomaterials produced by Escherichia coli K-12 are stable and remain as BioSe-Nanospheres under thermophilic conditions, while those produced by anaerobic granular sludge transform to BioSe-Nanorods, due to a lower quantity of proteins coating these nanoparticles, which has been verified by proteomics analysis as well as using chemically synthesized selenium nanomaterials. Furthermore, the presence of Bacillus safensis JG-B5T transform the purified BioSe-Nanospheres produced by E. coli K-12 to BioSe-Nanorods, though they are not transformed in the absence of B. safensis JG-B5T. This is due to the production of peptidases by B. safensis JG-B5T that cleaves the protein coating the BioSe-Nanospheres produced by E. coli K-12, leading to their transformation to trigonal BioSe-Nanorods, which is the thermodynamically more stable state. These findings suggest that the fate of selenium and probably other redox-active elements released from the biological wastewater treatment units needs to be reevaluated and improved by including microbial criteria for better accuracy.

Temporal Influences on Selenium Partitioning, Trophic Transfer, and Exposure in a Major U.S. River

Hydrologic and irrigation regimes mediate the timing of selenium (Se) mobilization to rivers, but the extent to which patterns in Se uptake and trophic transfer through recipient food webs reflect the temporal variation in Se delivery is unknown. We investigated Se mobilization, partitioning, and trophic transfer along approximately 60 river miles of the selenium-impaired segment of the Lower Gunnison River (Colorado, USA) during six sampling trips between June 2015 and October 2016. We found temporal patterns in Se partitioning and trophic transfer to be independent of those in dissolved Se concentrations and that the recipient food web sustained elevated Se concentrations from earlier periods of high Se mobilization. Using an ecosystem-scale Se accumulation model tailored to the Lower Gunnison River, we predicted that the endangered Razorback Sucker (Xyrauchen texanus) and Colorado Pikeminnow (Ptychocheilus lucius) achieve whole-body Se concentrations exceeding aquatic life protection criteria during periods of high runoff and irrigation activity (April-August) that coincide with susceptible phases of reproduction and early-life development. The results of this study challenge assumptions about Se trophodynamics in fast-flowing waters and introduce important considerations for the management of Se risks for biota in river ecosystems.

Fish as bioindicators: coal and mercury pollution in Colombia's ecosystems

Mining in Colombia affects 488,672 ha (298,391 in coal mining and 190,281 in gold mining). However, Colombia has insufficient studies on mining and its repercussions, which limits estimates of mining impacts on ecosystems and the human population. Due to the rise of mining activities in Colombia, the negative impacts generated by coal and Hg will also continue to increase. This review analyzes national information levels on coal and Hg in island/coastal/marine as well as freshwater ecosystems and human groups using fishery resources as a framework. This is because fish are the main source of animal protein in marine coastal-island and mainland communities. Here, 15 of 32 Colombian departments have records on total mercury (THg) in water, sediments, fish, and human communities. Around 205 ton/year of mercury is discharged into the ecosystem. In human hair for example (15.3 to 50.15 μg/g), mercury exceeds the international maximum levels allowed (ILA) and the national standard (5.0 μg/g). Mercury levels in freshwater fish show 3.3 μg/g of THg and levels in marine and coastal-island fish are 1.2 μg/g THg exceeding the ILA (0.5 μg/g) standard for fish that will be consumed. Carnivorous species have a THg between 0.04 and 2.55 μg/g suggesting bioaccumulation and magnification of heavy metals. These findings were then compared with available international information.

Contaminant Subsidies to Riparian Food Webs in Appalachian Streams Impacted by Mountaintop Removal Coal Mining

Selenium is highly elevated in Appalachian streams and stream organisms that receive alkaline mine drainage from mountaintop removal coal mining compared to unimpacted streams in the region. Adult aquatic insects can be important vectors of waterborne contaminants to riparian food webs, yet pathways of Se transport and exposure of riparian organisms are poorly characterized. We investigated Se concentrations in stream and riparian organisms to determine whether mining extent increased Se uptake in stream biofilms and insects and if these insects were effective Se biovectors to riparian spiders. Biofilm Se concentration increased (p = 0.006) with mining extent, reaching a maximum value of 16.5 μg/g of dw. Insect and spider Se increased with biofilm Se (p = 0.004, p = 0.003), reaching 95 and 26 μg/g of dw, respectively, in mining-impacted streams. Adult insect biomass was not related to mining extent or Se concentrations in biofilm. Even though Se concentrations in aquatic insects were significantly and positively related to mining extent, aquatic insect Se flux was not associated with mining extent because the mass of emerging insects did not change appreciably over the mining gradient. Insect and spider Se concentrations were among the highest reported in the literature, regularly exceeding the bird Se dietary risk threshold of 5 μg/g of dw. Risks of Se exposure and toxicity related to mining are thus not constrained to aquatic systems but extend to terrestrial habitats and food webs.

Protection of rice against Nilaparvata lugens by direct toxicity of sodium selenate

Nilaparvata lugens is one of the most notorious pest insects of cultured rice, and outbreaks of N. lugens cause high economic losses each year. While pest control by chemical pesticides is still the standard procedure for treating N. lugens infections, excessive use of these insecticides has led to the emergence of resistant strains and high pesticide residues in plants for human consumption and the environment. Therefore, novel and environment-friendly pest control strategies are needed. In previous studies, selenium was shown to protect selenium-accumulating plants from biotic stress. However, studies on nonaccumulator (crop) plants are lacking. In this study, rice plants (Oryza sativa, Nipponbare) were treated with sodium selenate by seed priming and foliar spray and then infested with N. lugens. Brown planthoppers feeding on these plants showed increased mortality compared to those feeding on control plants. Treatment of the plants with sodium selenate did not affect the enzymes involved in the biosynthesis of the plant stress hormones jasmonic acid and salicylic acid, suggesting that the observed insect mortality cannot be attributed to the activation of these hormonal plant defenses. Feeding assays using an artificial diet supplemented with sodium selenate revealed direct toxicity toward N. lugens. With a low concentration of 6.5 ± 1.5 µM sodium selenate, half of the insects were killed after 3 days. In summary, sodium selenate treatment of plants can be used as a potential alternative pest management strategy to protect rice against N. lugens infestation through direct toxicity.

Selenium Bioaccumulation Across Trophic Levels and Along a Longitudinal Gradient in Headwater Streams

Toxic effects of selenium (Se) contamination in freshwaters have been well documented. However, study of Se contamination has focused on lentic and larger order lotic systems, whereas headwater streams have received little scrutiny. In central Appalachia, surface coal mining is a common Se source to headwater streams, thus providing a useful system to investigate Se bioaccumulation in headwater food chains and possible longitudinal patterns in Se concentrations. Toward that end, we assessed Se bioaccumulation in 2 reference and 4 mining-influenced headwater streams. At each stream, we sampled ecosystem media, including streamwater, particulate matter (sediment, biofilm, leaf detritus), benthic macroinvertebrates, salamanders, and fish, every 400 m along 1.2- and 1.6-km reaches. We compared media Se concentrations within and among streams and evaluated longitudinal trends in media Se concentrations. Selenium concentrations in sampled media were higher in mining-influenced streams compared with reference streams. We found the highest Se concentrations in benthic macroinvertebrates; however, salamanders and fish bioaccumulated Se to potentially harmful levels in mining-influenced streams. Only one stream demonstrated dilution of streamwater Se with distance downstream, and few longitudinal patterns in Se bioaccumulation occurred along our study reaches. Collectively, our results provide a field-based assessment of Se bioaccumulation in headwater food chains, from streamwater to fish, and highlight the need for future assessments of Se effects in headwater streams and receiving downstream waters. Environ Toxicol Chem 2020;39:692-704. © 2020 SETAC.

Selenium Biofortification and Antioxidant Activity in Cordyceps militaris Supplied with Selenate, Selenite, or Selenomethionine

Selenium (Se) is an essential trace element with multiple functions that may help mitigate adverse health conditions. Cordyceps militaris is an edible mushroom with medicinal properties. The experiment was conducted under artificial cultivation, with five Se concentrations (0, 5, 10, 20, and 40 μg g^-1) and three forms of Se (selenate, selenite, and selenomethionine). C. militaris can absorb inorganic from the substrate and convert it to organic Se compounds (selenocystine, selenomethionine, and an unknown species) in fruiting bodies. Compared with the control treatment, Se applications (40 μg g^-1 selenate and selenite) significantly increased the Se concentration in fruiting bodies by 130.9 and 128.1 μg g^-1, respectively. The biofortification with selenate and selenite did not affect fruiting body production, in some case, but did enhance the biological efficiency. Moreover, the abundance of cordycepin and adenosine increased, while the amino acid contents remained relatively stable. Meanwhile, Se-biofortified C. militaris showed effective antioxidant activities. These results suggest that Se-biofortified C. militaris fruiting bodies may enhance human and animal health when it was included as part of a healthy diet or used as Se supplements.

Selenium dynamics in headwater streams of the central Appalachian coalfield

Coal mining can cause selenium (Se) contamination in US Appalachian streams, but linkages between water-column Se concentrations and Se bioaccumulation within Appalachian headwater streams have rarely been quantified. Using elevated specific conductance (SC) in stream water as an indicator of mining influence, we evaluated relationships between SC and Se concentrations in macroinvertebrates and examined dynamics of Se bioaccumulation in headwater streams. Twenty-three Appalachian streams were categorized into 3 stream types based on SC measurements: 1) reference streams with no coal-mining history; 2) mining-influenced, high-SC streams; and 3) mining-influenced, low-SC streams. Selenium concentrations in macroinvertebrates exhibited strong positive associations with both SC and dissolved Se concentrations in stream water. At 3 streams of each type, we further collected water, particulate matter (sediment, biofilm, leaf detritus), and macroinvertebrates and analyzed them for Se during 2 seasons. Enrichment, trophic transfer, and bioaccumulation factors were calculated and compared among stream types. Particulate matter and macroinvertebrates in mining-influenced streams accumulated high Se concentrations relative to reference streams. Concentrations were found at levels indicating Se to be a potential environmental stressor to aquatic life. Most Se enrichment, trophic transfer, and bioaccumulation factors were independent of season. Enrichment factors for biofilm and sediments and bioaccumulation factors for macroinvertebrate predators varied negatively with water-column Se. Our results increase scientific understanding of Se bioaccumulation processes in Appalachian headwater streams. Environ Toxicol Chem 2018;37:2714-2726. © 2018 SETAC.

Mountaintop Removal Coal Mining and Emergent Cases of Psychological Disorder in Kentucky

Although mountaintop removal (MTR) coal extraction techniques have been employed in Appalachia for decades, relatively little research has examined its potential psychological impact on people living in close proximity to MTR activity. The current study taps the State Emergency Department Database (Healthcare Cost and Utilization Project, Kentucky State Emergency Department Database, 2008) to examine the relative risk for diagnoses of depressive, substance use, and anxiety disorders originating in areas with and without MTR activity. Logistical regression analyses, controlling for ethnicity, rurality, mean income, and gender, indicated that MTR independently predicts greater risk for depressive (OR 1.37) and substance use disorders (OR 1.41), but not anxiety disorders. Overall, these findings have public health policy implications, build on other evidence of increased risk of negative mental health outcomes related to MTR, and lend some support to the validity of solastalgia related to environmental change.

Occupancy and Detection of Clinch Dace Using Two Gear Types

The Clinch Dace Chrosomus sp. cf. saylori, discovered in 1999, is an undescribed headwater fish species of global conservation concern with a limited distribution in two counties in southwest Virginia. Highly efficient sampling gears are key to monitoring headwater fish assemblages in Appalachia, including those containing Clinch Dace. Additional information is needed regarding the habitat requirements of the species to understand responses to future mining and logging activities in the region. An occupancy modeling framework is useful to account for incomplete detection, with multiple sampling gears in presence–absence surveys for cryptic or rare species. We detected Clinch Dace at 13 of 70 sites. Occupancy corrected for imperfect detection probability did not differ from naïve occupancy estimates and was 0.19. Clinch Dace occurred in streams with higher substrate embeddedness and catchment forest cover. Backpack electrofishing had a 55% higher probability of detecting Clinch Dace in a 50-m subreach than minnow traps. Appropriate management actions for this species may focus on preserving forested cover in occupied watersheds and monitoring the future impact of surface mining activities that increase total dissolved solids. Sampling protocols for the imperiled Clinch Dace can incorporate both gears and adjust sampling effort to maximize species detection in specific habitats and with specific research goals.

Selenium Ecotoxicology in Freshwater Lakes Receiving Coal Combustion Residual Effluents: A North Carolina Example

Anthropogenic activities resulting in releases of selenium-laden waste streams threaten freshwater ecosystems. Lake ecosystems demand special consideration because they are characterized by prolonged retention of selenium and continuous cycling of the element through the food chain, through which it becomes available to toxicologically susceptible egg-laying vertebrates. This study documents the current selenium burden of lakes in North Carolina (NC) with historic selenium inputs from nearby coal-fired power plants. We measured selenium concentrations in surface waters, sediment pore waters, and resident fish species from coal combustion residual (CCR)-impacted lakes and paired reference lakes. The data are related to levels of recent selenium inputs and analyzed in the context of recently updated federal criteria for the protection of aquatic life. We show that the Se content of fish from lakes with the highest selenium inputs regularly exceed these criteria and are comparable to those measured during historic fish extirpation events in the United States. Large legacy depositions of CCRs within reservoir sediments are likely to sustain Se toxicity for many years despite recent laws to limit CCR discharge into surface waters in NC. Importantly, the widespread use of high-selenium coals for electricity generation extends the potential risk for aquatic ecosystem impacts beyond U.S. borders.

Behaviour, development and metal accumulation in striped marsh frog tadpoles (Limnodynastes peronii) exposed to coal mine wastewater

Coal mining generates large quantities of complex effluent, and this often contains high levels of dissolved solids, suspended solids, metals, hydrocarbons, salts and other compounds. Substantial volumes of mine wastewater are periodically discharged into the environment, through both planned and accidental releases, and this raises concerns about the potential for adverse impacts on aquatic wildlife. There have been few attempts to explore sub-lethal effects of coal mine wastewater on amphibians compared to other organisms, and this is particularly true for Australian species. To address existing knowledge gaps, we exposed striped marsh frog (Limnodynastes peronii) tadpoles to 25, 50 and 100% coal mine wastewater collected from two holding dams (CMW1 and CMW2) located at an open cut mine in Central Queensland, Australia. The exposure lasted for four weeks, after which survival, growth and development, swimming behaviour, and concentrations of metals and metalloids in tail and liver tissues were assessed. Physico-chemical parameters varied considerably between sites, with higher turbidity, nutrients, total and dissolved organic carbon, alkalinity and arsenic (As) concentrations at CMW1, and higher conductivity, salinity, dissolved solids, hardness and sulfate levels at CMW2. There was no mortality in controls and less than 5% mortality in CMW1 treatments, whereas survival was significantly decreased in tadpoles exposed to CMW2 with 40 and 55% mortality in the 50 and 100% treatments, respectively. Development was significantly delayed in 100% CMW1 wastewater, but tadpole size (growth) was not influenced by the exposure. Hepatosomatic indices were significantly increased in tadpoles exposed to 25 and 50% CMW1 but not the 100% treatment group. Exposed tadpoles (predominantly those exposed to CMW1) exhibited increased activity after very short-term exposure (24h), but this did not persist as animals approached metamorphic climax. At the end of the experiment, tadpoles exposed to both wastewaters had elevated levels of selenium (Se), cobalt (Co) and As in tail and liver tissue compared to controls. Manganese (Mn) levels were also elevated in livers and tails of CMW2 exposed tadpoles. Hepatic tissue accumulated 8-9 times higher concentrations of Co, Mn and Se compared to tail tissue, irrespective of treatments. Future research is warranted to explore possible relationships between metal bioaccumulation, morpho-physiological effects during development, and subsequent higher-level outcomes related to individual performance and population fitness.

Locomotor and behavioural responses of empire gudgeons (Hypseleotris compressa) exposed to coal mine wastewater

Coal mining generates large quantities of complex effluent and may pose a threat to aquatic wildlife. Despite this, few studies have explored the consequences of exposure to mine wastewater on aquatic organisms, and this is particularly true for the Australian environment. We investigated sub-lethal behavioural responses in a native Australian fish exposed to wastewater from two releasing dams (CMW1 and CMW2) located at an open cut coal mine in Central Queensland. Swimming activity and movement of empire gudgeons (Hypseleotris compressa) were assessed during a two-week exposure using video-tracking software. Increased activity was observed in exposed fish after 7 and 14 days. Specifically, we found a significant increase in the mean velocity and mobility of fish exposed to CMW1 treatments. Exposed fish also spent on average 23% more time in the peripheral zone compared to controls after 14-d exposures. A similar response pattern was observed in fish exposed to CMW2, but differences between treated and control fish did not generally reach statistical significance. Alterations to normal swimming activity and movement patterns can be indicative of a stress response in fish, and could subsequently lead to negative population-level impacts by increasing the conspicuousness of exposed individuals to predators, or by altering foraging abilities. More research is warranted to explore relationships between behavioural and physiological outcomes, including endocrine disruption, and subsequent population-level outcomes in aquatic organisms at risk of exposure to coal process-affected water.

Microchemical analysis of selenium in otoliths of two West Virginia fishes captured near mountaintop removal coal mining operations

Otoliths, calcified inner ear structures, were collected from creek chubs (Semotilus atromaculatus) and green sunfish (Lepomis cyanellus) living in mountaintop mining-impacted and reference streams and analyzed for selenium (Se) content using laser ablation-inductively coupled mass spectrometry. Significant differences in otolith Se were found between the 2 fish species. Results from the present study suggest that a retrospective reconstruction of Se concentrations in muscle can be derived from Se concentrations in otoliths in creek chub but not green sunfish, exemplifying the importance of species differences when determining partitioning of Se among specific tissues. Green sunfish otoliths from all sites contained background (<1 μg/g) or low (1-4 μg/g) average concentrations of whole-otolith Se. In contrast, creek chub otoliths from the historically mined site contained much higher (≥5 μg/g) concentrations of Se than for the same species in the unmined site or for the green sunfish. These data suggest that body burdens of Se in fish can vary considerably over time and that both the timing of sampling and species choice could heavily influence Se assessments.

Threshold-dependent sample sizes for selenium assessment with stream fish tissue

Natural resource managers are developing assessments of selenium (Se) contamination in freshwater ecosystems based on fish tissue concentrations. We evaluated the effects of sample size (i.e., number of fish per site) on the probability of correctly detecting mean whole-body Se values above a range of potential management thresholds. We modeled Se concentrations as gamma distributions with shape and scale parameters fitting an empirical mean-to-variance relationship in data from southwestern West Virginia, USA (63 collections, 382 individuals). We used parametric bootstrapping techniques to calculate statistical power as the probability of detecting true mean concentrations up to 3 mg Se/kg above management thresholds ranging from 4 to 8 mg Se/kg. Sample sizes required to achieve 80% power varied as a function of management thresholds and Type I error tolerance (α). Higher thresholds required more samples than lower thresholds because populations were more heterogeneous at higher mean Se levels. For instance, to assess a management threshold of 4 mg Se/kg, a sample of eight fish could detect an increase of approximately 1 mg Se/kg with 80% power (given α=0.05), but this sample size would be unable to detect such an increase from a management threshold of 8 mg Se/kg with more than a coin-flip probability. Increasing α decreased sample size requirements to detect above-threshold mean Se concentrations with 80% power. For instance, at an α-level of 0.05, an 8-fish sample could detect an increase of approximately 2 units above a threshold of 8 mg Se/kg with 80% power, but when α was relaxed to 0.2, this sample size was more sensitive to increasing mean Se concentrations, allowing detection of an increase of approximately 1.2 units with equivalent power. Combining individuals into 2- and 4-fish composite samples for laboratory analysis did not decrease power because the reduced number of laboratory samples was compensated for by increased precision of composites for estimating mean conditions. However, low sample sizes (<5 fish) did not achieve 80% power to detect near-threshold values (i.e., <1 mg Se/kg) under any scenario we evaluated. This analysis can assist the sampling design and interpretation of Se assessments from fish tissue by accounting for natural variation in stream fish populations.