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A Field-Based Aquatic Life Benchmark for Conductivity in Central Appalachian Streams (Final Report).
Abstract
EXECUTIVE SUMMARY: This report uses field data to derive an aquatic life benchmark for conductivity that can be applied to waters in the Appalachian Region that are dominated by salts of Ca2+, Mg2+, SO42− and HCO3– at a circum-neutral to mildly alkaline pH. This benchmark is intended to protect the aquatic life in the region. It is derived by a method modeled on the EPA’s standard methodology for deriving water-quality criteria (i.e., Stephan et al., 1985). In particular, the methodology was adapted for use of field data. Field data were used because sufficient and appropriate laboratory data were not available and because high-quality field data were available to relate conductivity to effects on aquatic life. This report provides scientific evidence for a conductivity benchmark in a specific region rather than for the entire United States.
The method used in this report is based on the standard methodology for deriving water-quality criteria, as explained in Stephan et al. (1985), in that it used the 5th centile of a species sensitivity distribution (SSD) as the benchmark value. SSDs represent the response of aquatic life as a distribution with respect to exposure. Data analysis followed the standard methodology in aggregating species to genera and using interpolation to estimate the centile. It differs primarily in that the points in the SSDs are extirpation concentrations (XCs) rather than median lethal concentrations (LC50s) or chronic values. The XC is the level of exposure above which a genus is effectively absent from water bodies in a region. For this benchmark value, the 95th centile of the distribution of the probability of occurrence of a genus with respect to conductivity was used as a 95th centile extirpation concentration. Hence, this aquatic life benchmark for conductivity is expected to avoid the local extirpation of 95% of native species (based on the 5th centile of the SSD) due to neutral to alkaline effluents containing a mixture of dissolved ions dominated by salts of SO42− and HCO3−. Because it is not protective of all genera and protects against extirpation rather than reduction in abundance, this level is not fully protective of sensitive species or higher quality, exceptional waters designated by state and federal agencies.
This field-based method has several advantages. Because it is based on biological surveys, it is inherently relevant to the streams where the benchmark may be applied and represents the actual aquatic life use in these streams. Another advantage is that the method assesses all life stages and ecological interactions of many species. Further, it represents the actual exposure conditions for elevated conductivity in the region, the actual temporal variation in exposure, and the actual mixture of ions that contribute to salinity as measured by conductivity.
The disadvantages of field data result from the fact that exposures are not controlled. As a result, the causal nature of the relationship between conductivity and the associated biological impairments must be assessed. Also, any variables that are correlated with conductivity and the biotic response may confound the relationship of biota to conductivity. Assessments of causation and confounding were performed and are presented in the appendices. They demonstrate that conductivity can cause impairments and the relationship between conductivity and biological responses apparently is not appreciably confounded.
The chronic aquatic life benchmark value for conductivity derived from all-year data from West Virginia is 300 μS/cm. It is applicable to parts of West Virginia and Kentucky within Ecoregions 68, 69, and 70 (Omernick, 1987). It is expected to be applicable to the same ecoregions extending into Ohio, Pennsylvania, Tennessee, Virginia, Alabama, and Maryland, but data from those states have not been analyzed. This is because the salt matrix and background is expected to be similar throughout the ecoregions. The benchmark may also be appropriate for other nearby ecoregions, such as Ecoregion 67, but it has only been validated for use in Ecoregions 68, 69, and 70 at this time. This benchmark level might not apply when the relative concentrations of dissolved ions are not dominated by salts of Ca2+, Mg2+, SO42− and HCO3– or the natural background exceeds the benchmark. However, the salt mixture dominated by salts of SO42− and HCO3− is believed to be an insurmountable physiological challenge for some species.
... Coal mining operations have traditionally only been regulated for the following water quality parameters under the Surface Mining Control and Reclamation Act (SMCRA) and the Clean Water Act (CWA): pH, Fe, and total suspended solids (TSS). In recent years, the US Environmental Protection Agency (EPA) has recommended a regulatory effluent limit on specific conductance (SC) of 500 S/cm based on a study that examined the correlation between SC and aquatic health in mine impaired waters (Cormier et al., 2011). ...
... The goal of this study was to test the feasibility of using various nanofiltration membranes to reduce SC and TDS levels in coal mining waters that are characteristic of southwestern VA. As a means of evaluating each trial, the resulting SC value after each treatment was compared to the proposed upper limit of 500 S/cm, as recommended by Cormier et al. (2011). The ionic makeup of the filtrate from each treatment was compared to that of the source water in order to understand the removal of each ion. ...
... Coal mining operations have traditionally only been regulated for the following water quality parameters under the Surface Mining Control and Reclamation Act (SMCRA) and the Clean Water Act (CWA): pH, Fe, and total suspended solids (TSS). In recent years, the US Environmental Protection Agency (EPA) has recommended a regulatory effluent limit on specific conductance (SC) of 500 S/cm based on a study that examined the correlation between SC and aquatic health in mine impaired waters (Cormier et al., 2011). ...
... The goal of this study was to test the feasibility of using various nanofiltration membranes to reduce SC and TDS levels in coal mining waters that are characteristic of southwestern VA. As a means of evaluating each trial, the resulting SC value after each treatment was compared to the proposed upper limit of 500 S/cm, as recommended by Cormier et al. (2011). The ionic makeup of the filtrate from each treatment was compared to that of the source water in order to understand the removal of each ion. ...
... In freshwater systems, even low levels of salinization can decrease decomposer activity and growth (Tyree et al. 2016), and although salts contain essential nutrients that organisms need for survival, reproduction, and growth, salts in freshwater ecosystems must balance these requirements with osmoregulation, which often results in high levels of mortality after even relatively low increases in conductivity (Hart 1985;Cormier et al. 2011). Leachate conductivity and ion content was not surprisingly highest when NaCl was added in both water and leaf litter (NaCl W + NaCl L ). ...
Understanding the factors that mediate carbon (C) cycling is increasingly important as anthropogenic activities and climate change alter ecosystems. Decomposition rates mediate C cycling and are in part regulated by sodium (Na) where Na is limiting up to some threshold after which Na becomes stressful and reduces decomposition rates (i.e., the Sodium Subsidy-Stress hypothesis). An overlooked pathway by which decomposers encounter increased salts like NaCl is through plants, which often take up Na in proportion to soil concentrations. Here we tested the hypothesis that Na addition through litter (detritus) and water and their interaction would impact detrital processing and leachate chemistry. Laboratory riparian soil mesocosms received either artificial litter (100% cellulose sponges) soaked in 0.05% NaCl (NaClL) or just H2O (H2OL: control) and half of each litter treatment received weekly additions of 150 ml of either 0.05% NaCl water (NaClW) or just H2O (H2OW: control). After 8 weeks decomposition was higher in NaCl addition treatments (both NaClL and NaClW and their combo) than controls (H2OL + H2OW) but reflected a unimodal relationship where the saltiest treatment (NaClL + NaClW) was only marginally higher than controls indicating a subsidy-stress response. Previous studies in this system found that Na addition in either water or litter decreased decomposition. However, differences may reflect a phenology of Na demand where Na-limitation increases in the spring (this study). These results indicate that our understanding of how Na impacts detrital processes, C cycling, and aquatic-terrestrial linkages necessitates incorporation of temporal dynamics.
... However, it was surprising that we did not see a stronger (statistical) response in the first year of the study when SGD was most intense. The values for conductance in particular were well below levels considered impaired on average (i.e., < 300 µS/cm; Cormier et al., 2011;Pond et al., 2013). Nevertheless, the increase in average specific conductance in 2014 at DS sites is noteworthy. ...
diverged in similarity downstream compared to upstream of impacts in the first and last years of the study when SGD activity was elevated. Assemblage divergence was related to variation in water quality. Indicator species analysis linked a few key taxa to un-impacted conditions in the first year of the study; tolerant taxa were indicators for impacted conditions later in the study. Our study links SGD to weak negative changes in water quality and benthic macroin-vertebrates, which may have negative consequences to food quality for wildlife that rely on aquatic prey within forested systems.
... mg/L; COD Mn =2.40 mg/L respectively). High EC (283 μS/cm) have been proved to limit the diversity of intolerant macroinvertebrate taxa [25] , which was consistent with U.S. EPA also recommended the benchmark value of conductivity should be set at 300 μS/cm to protect the stream biota [26] . Similarly, high nutrient concentrations (NH 3 -N>0.12 ...
Transformations of land use from natural to anthropic type have been recognized as a significant trigger which degenerate the aquatic ecological quality seriously. However, there was still lack of enough evidence which the extent of changes in land use should be set as a biodiversity conservation target to protect aquatic ecosystem. To understand the corresponding variations of aquatic organisms to environmental gradients and set the conservation threshold values for land use, data of physicochemical parameters and macroinvertebrate communities were sampled in the Hun-Tai River Basin during 2009 and 2010. The main objectives of the present study were (i) to explore limiting factors that affect the distribution of macroinvertebrate communities with land use gradients, (ii) to estimate thresholds for the conservation of macroinvertebrate communities derived from generalized additive models (GAMs) and Threshold Indicator Taxa ANalysis (TITAN), respectively. The results indicated that macroinvertebrate communities’ structure and integrity were strongly negative with nutrient, organic contaminants content, %CropArea and %ImperviousArea. Under a precaution perspective and given current levels of land use, this research might provide some useful strategies for appropriate land exploitation management and improving water quality and biodiversity conservation in river ecological restoration.
... For example, taxa representing all aquatic insect orders can show growth sensitivity at 1 g/L total dissolved solids in Australian streams and wetlands (Hart et al. 1991). In the United States, a conductivity benchmark of roughly 0.2 g/L total dissolved solids has been identified as protective to aquatic life (Cormier et al. 2011). Consistent with the field studies described in Sect. ...
At low concentrations, trace metals are critical for sustaining life on Earth. However, at high concentrations, they become a global contaminant with particularly strong effects on freshwater communities. These effects can propagate to terrestrial ecosystems in part by altering production and community structure of adult aquatic insect emergence and aquatic insect-mediated metal fluxes to terrestrial insectivores. Here we highlight mechanisms driving effects of trace metals on aquatic organisms in general, aquatic insects specifically, and insectivorous consumers at the land-water interface. Specifically, we focus on how trace metals impact and bioaccumulate in aquatic organisms and communities and how these changes propagate through aquatic food web interactions and insect metamorphosis to alter fluxes of aquatically derived prey and trace metals to terrestrial consumers. Ultimately, trace metals impact food webs at the land-water interface by altering aquatic insect prey composition and availability for aquatic insectivores and by reducing aquatic insect subsidies to terrestrial consumers, and not by increasing exposure to trace metals in prey. Exposure of terrestrial insectivores to trace metals in prey is decoupled from aqueous concentrations due to high rates of metal excretion during insect metamorphosis from aquatic larvae to terrestrial adult. These effects increase reliance of aquatic insectivores on terrestrial insect prey subsidies and/or lead to declines and behavioral changes in terrestrial insectivore populations.
... The use of field data is recommended by the U.S. Environmental Protection Agency Science Advisory Board for the derivation of ecological risks of chemicals. 129 This study demonstrates that the field-based ...
Ecological risks (ER) of pollutants are typically assessed using species sensitivity distributions (SSDs), based on effect concentrations obtained from bioassays with unknown representativeness for field conditions. Alternatively, monitoring data relating breeding success in bird populations to egg concentrations may be used. In this study, we developed a procedure to derive SSDs for birds based on field data of egg concentrations and reproductive success. As an example, we derived field-based SSDs for p,p’-DDE and polychlorinated biphenyls (PCBs) exposure to birds. These SSDs were used to calculate ERs for these two chemicals in the Great Lakes district and the Arctic. First, we obtained field data of p,p’-DDE and PCBs egg concentrations and reproductive success from the literature. Second, these field data were used to fit exposure-response curves along the upper boundary (right margin) of the response’s distribution (95th quantile), also called quantile regression analysis. The upper boundary is used to account for heterogeneity in reproductive success induced by other external factors. Third, the species-specific EC10/50s obtained from the field-based exposure-response curves were used to derive SSDs per chemical. Finally, the SSDs were combined with specific exposure data for both compounds in the two areas to calculate the ER. We found that the ERs of combined exposure to these two chemicals were a factor of 5 – 35 higher in the Great Lakes compared to Arctic regions. Uncertainty in the species-specific exposure-response curves and related SSDs was mainly caused by the limited number of field exposure-response data for bird species. With sufficient monitoring data, our method can be used to quantify field-based ecological risks for other chemicals, species groups and regions of interest.
The rivers of Appalachia (United States) are among the most biologically diverse freshwater ecosystems in the temperate zone and are home to numerous endemic aquatic organisms. Throughout the Central Appalachian ecoregion, extensive surface coal mines generate alkaline mine drainage that raises the pH, salinity, and trace element concentrations in downstream waters. Previous regional assessments have found significant declines in stream macroinvertebrate and fish communities after draining these mined areas. Here, we expand these assessments with a more comprehensive evaluation across a broad range of organisms (bacteria, algae, macroinvertebrates, all eukaryotes, and fish) using high‐throughput amplicon sequencing of environmental DNA (eDNA). We collected water samples from 93 streams in Central Appalachia (West Virginia, United States) spanning a gradient of mountaintop coal mining intensity and legacy to assess how this land use alters downstream water chemistry and affects aquatic biodiversity. For each group of organisms, we identified the sensitive and tolerant taxa along the gradient and calculated stream specific conductivity thresholds in which large synchronous declines in diversity were observed. Streams below mining operations had steep declines in diversity (−18 to −41%) and substantial shifts in community composition that were consistent across multiple taxonomic groups. Overall, large synchronous declines in bacterial, algal, and macroinvertebrate communities occurred even at low levels of mining impact at stream specific conductivity thresholds of 150–200 µS/cm that are substantially below the current U.S. Environmental Protection Agency aquatic life benchmark of 300 µS/cm for Central Appalachian streams. We show that extensive coal surface mining activities led to the extirpation of 40% of biodiversity from impacted rivers throughout the region and that current water quality criteria are likely not protective for many groups of aquatic organisms.
This chapter evaluates the case for inclusion of terrestrial-derived detrital endpoints, which are those metrics that describe changes to detrital pathways in freshwater ecosystems, into the regulatory framework for US wadeable streams. Terrestrial detritus consisting of dead plant and animal matter is an important resource subsidy to forested-aquatic stream ecosystems, and detrital form and function can be negatively modified by elevated nutrient and salt contaminants in aquatic ecosystems. Of concern to regulators, a large proportion of US wadeable streams with poor water quality and biological condition due to nutrient and salt contamination occur in temperate-forested biomes where detritus is essential for aquatic life. This chapter reviews existing US water quality endpoint response characteristics and proposes a suite of endpoints derived from a literature review that can be used to detect changes in detrital-based wadeable streams caused by elevated nutrient and salt contaminants. These detrital endpoints may serve as sentinels of impending species loss and better allow managers to detect and prevent changes to critical ecosystem functions. Furthermore, this review illustrates how research on contaminants and ecological subsidies in linked aquatic-terrestrial ecosystems can be used to inform management of these ecosystems.
An environmental concern at coal preparation operations is the release of elements resulting from the oxidation or dissolution of certain minerals contained in the process waste streams. Using a standard conductivity test, the electrical conductivity (EC) of water samples obtained from mixing with various particle size and density fractions of a given plant waste material were measured as an indicator of total dissolved solids. The net neutralization potential (NNP) of the fractions were also measured to predict the pH of the supernatant upon disposal. As a result, the particle size and density fractions contributing to high EC levels were identified with the objective of potentially extracting and isolating these fractions which can significantly reduce the negative environmental impacts. The results showed that the EC generated from coarse refuse streams were significantly higher than the values obtained from fine refuse streams. Based on the NNP values, the coarse refuse stream generates highly acidic pH, while the fine refuse in contact with water produces circumneutral pH. Furthermore, the high specific gravity (>2.68) fractions which comprised less than 10% of the coal waste streams were found to be the primary source of elevated EC levels. The remaining fractions were found to be of minimal environmental concern. Based on the obtained results, modifications to the coal preparation plants were proposed to minimize the environmental concerns of coal waste disposal. Modifications include pyrite removal from the spiral refuse and desulfurization of flotation feed and sieve bend underflow streams using low-cost mineral spiral circuitry. After the segregation, the pyrite (high density) fraction, which encompasses around 1% of the coarse and fine refuse streams, will be isolated/encapsulated and the fine refuse stream dewatered and co-disposed with the coarse refuse stream. The proposed modifications to the processing and disposal practices not only minimize the generation of acid mine drainage thereby reducing the release of trace elements and EC of the discharged water, but also enhances the recovery and quality of the final clean coal product.
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