Geology topics

Christopher A. Mebane

Publications and source records attributed to Christopher A. Mebane.

At least 19 recordsLinked to original sources

USGS2025

Fate and effects to the benthic community of a copper treatment to eradicate invasive mussels in a large western river, USA

Copper-based chemical treatments are commonly used to eradicate invasive mussels in small ponds and lakes, but their use in large rivers has been limited. In 2023, in response to a detection of invasive quagga mussels, a 10-km reach of the Snake River (Idaho, USA), was treated with an unprecedented 19,300 kg of chelated copper molluscicide to a target concentration of 1,000 µg/L for 10 days. We assessed the transport and fate of the copper and its exposure and effects on the nontarget benthic community downstream. Water samples were collected at seven locations throughout the treatment period, and sediment, periphyton, and benthic macroinvertebrates were collected pre- and posttreatment. Nearly half of the original mass of copper was removed from the water column via sedimentation, sorption to algae, or biological uptake within the 10-km treatment reach and the first 15 km downstream. Even so, dissolved copper concentrations exceeded the acute toxicity threshold at least as far as 28 km downstream for more than 2 weeks. Sediment copper increased by up to 8.3-fold, exceeding the consensus-based sediment quality threshold effect concentration at several sites. Effects on benthic macroinvertebrates varied by taxa. From 0–28 km downstream, invertebrate abundances decreased 52%–94%, with gastropods among the most affected. Of the unique taxa present at these sites pretreatment, 52%–64% were not found posttreatment but were replaced by other taxa, indicating a reorganization of the base of the food web. Additionally, from 0–15 km downstream, the percentage of individuals from tolerant taxa increased two to15-fold. Findings from this study can help watershed managers plan future invasive mussel responses while protecting culturally, economically, and ecologically important nontarget species in large rivers.

Idaho↗

USGS2025

Bioaccumulation and trophic transfer of selenium in a large oligotrophic river

In flowing waters with elevated selenium concentrations, fish are often considered to be at risk from selenium toxicity owing to dietary exposure and accumulation in ovary tissues and subsequent deformities in developing larvae. We studied selenium throughout components of the aquatic food webs at geomorphically distinct locations along the oligotrophic Kootenai River (Montana and Idaho, USA), a river with moderately elevated dissolved selenium concentrations (~ 1 µg/L). Components included water, sediment, freshly accrued biofilms, in-situ periphyton, sestonic detritus, aquatic invertebrates, and fish, with spring and fall sampling. Selenium concentrations were similar among the sediment, biofilm, periphyton, and detritus samples with most concentrations ranging between 0.5 to 2.0 (mg/kg dry weight (dw)). Among the aquatic invertebrates, the highest selenium concentrations were observed in Paraleptophlebia sp. mayflies (>15 mg/kg dw) and oligochaetes (>30 mg/kg dw). Selenium in chironomids was higher in the spring than fall, but otherwise, no consistent concentration patterns with season or feeding traits were observed. Fish tissue selenium concentrations were highly variable among species and tissue type. Selenium in fish tissues tended to be highest in livers of rainbow trout and mountain whitefish relative to egg/ovary, muscle, and carcass tissue. With northern pikeminnow, redside shiner, and slimy sculpin, selenium concentrations tended to be highest in ovary tissues. For example, selenium in rainbow trout livers ranged from an average (range) of 37 (4.5 to 151) compared to 8.7 (2.7 to 12.3) in northern pikeminnow livers. Egg/ovary concentrations ranged from a high of 26 (10.7 to 64) in redside shiner in contrast to 12.2 (6.9 to 17) mg/kg dw in slimy sculpin. A drawback of the fish-tissue approach to monitoring and managing selenium risks in freshwaters is the need to kill multiple fish per site and event. Potential alternative monitoring approaches are illustrated using aquatic invertebrates or using the food web monitoring results to derive monitoring targets for selenium in water or invertebrate tissue that could avoid the need to kill fish to assess whether fish protection guidelines are met.

Idaho, Montana↗

USGS2023

Bioavailability and toxicity models of copper to freshwater life: The state of regulatory science

Efforts to incorporate bioavailability adjustments into regulatory water quality criteria in the United States have included four major procedures: hardness-based single-linear regression equations, water-effect ratios (WERs), biotic ligand models (BLMs), and multiple-linear regression models (MLRs) that use dissolved organic carbon, hardness, and pH. The performance of each with copper (Cu) is evaluated, emphasizing the relative performance of hardness-based versus MLR-based criteria equations. The WER approach was shown to be inherently highly biased. The hardness-based model is in widest use, and the MLR approach is the US Environmental Protection Agency's (USEPA's) present recommended approach for developing aquatic life criteria for metals. The performance of criteria versions was evaluated with numerous toxicity datasets that were independent of those used to develop the MLR models, including olfactory and behavioral toxicity, and field and ecosystem studies. Within the range of water conditions used to develop the Cu MLR criteria equations, the MLR performed well in terms of predicting toxicity and protecting sensitive species and ecosystems. In soft waters, the MLR outperformed both the BLM and hardness models. In atypical waters with pH <5.5 or >9, neither the MLR nor BLM predictions were reliable, suggesting that site-specific testing would be needed to determine reliable Cu criteria for such settings. The hardness-based criteria performed poorly with all toxicity datasets, showing no or weak ability to predict observed toxicity. In natural waters, MLR and BLM criteria versions were strongly correlated. In contrast, the hardness-criteria version was often out of phase with the MLR and, depending on waterbody and season, could be either strongly overprotective or underprotective. The MLR-based USEPA-style chronic criterion appears to be more generally protective of ecosystems than other models.

Environmental Toxicology and Chemistry↗

USGS2022

The capacity of freshwater ecosystems to recover from exceedances of aquatic life criteria

In the United States, national chemical water quality criteria for the protection of aquatic life assume that aquatic ecosystems have sufficient resiliency to recover from criteria exceedences occurring up to once every 3 years. This resiliency assumption was critically reviewed through two approaches: 1) synthesis of case studies and 2) population modeling. The population modeling examined differences in recovery of species with widely different life histories. One invertebrate ( Hyalella azteca ) and four fish species were modeled (fathead minnow, brook trout, lake trout, and shortnose sturgeon) with various disturbance magnitudes and intervals. The synthesis of ecosystem case studies showed generally faster recoveries for insect communities rather than fish, and recoveries from pulse (acute) disturbances were often faster than recoveries from press (chronic) disturbances. When the recovery dataset excluded severe disturbances that seemed unrepresentative of common facility discharge upsets that might cause criteria exceedences, the median recovery time was 1 year, 81% of the cases were considered recovered within 3 years, and 95% were considered recovered within 10 years. The modeling projected that short-lived fish species with high recovery times could thrive despite enduring 50% mortality disturbances every other year. However, long-lived fish species had longer recovery times and declined under the 1 disturbance every 3 years scenario. Overall, the analyses did not refute the long-standing judgements that 3 years is generally sufficient for recovery from non-repetitive, moderate intensity disturbances of a magnitude up to 2X the chronic criteria in waters without other pollution sources or stresses. However, these constraints may not always be met and if long-lived fish species are a concern, longer return intervals such as 5 to 10 years could be indicated.

Environmental Toxicology and Chemistry↗

USGS2022

The protectiveness of aquatic life criteria for threatened or endangered aquatic species: Cadmium in California

In the United States, conflicts can arise between the processes to derive aquatic life criteria (ALC) for chemicals under the Clean Water Act (CWA) and the evaluation procedures used in Endangered Species Act (ESA) consultations on the protectiveness of those criteria for protected species. This paper examines the roots of, and possible reconciliation of, one longstanding conflict over cadmium aquatic life criteria in California. This case study includes 1) an overview of occurrences of cadmium in the aquatic environment, 2) factors affecting toxicity of cadmium to aquatic life, 3) a contrast between the analytical procedures of CWA aquatic life criteria derivation and ESA consultation, 4) quantitative estimates of no-effect concentrations of cadmium for 44 ESA listed species in comparison with updated aquatic life criteria, and 5) concludes with suggestions to update California’s aquatic life criteria for cadmium that would be more protective of sensitive ESA listed species. A root cause of conflict is the different levels of biological organization that are the focus of CWA and ESA procedures. The CWA ALC are intended to protect diverse ecosystems by protecting at least 95% of the species richness in communities, allowing that it is acceptable for some species in the residual most sensitive 5% of the community richness to be harmed or even locally extirpated so long as they are not societally important species. The ESA is charged with minimizing harm to individual organisms and disallows increasing risk of extinction or impeding recovery of protected species. With cadmium in California, these procedures converge because some of the most sensitive species to cadmium happen to be surrogates for protected species (acute responses of steelhead/rainbow trout, Oncorhynchus mykiss , and chronic responses of threespine stickleback, Gasterosteus aculeatus ). The present review concludes that while the superseded 1996 cadmium criteria versions would not be fully protective for up to half of the 44 ESA listed aquatic species in California, the updated 2016 versions would be more protective. Still, the review shows that the updated acute criteria would only fully protect the less sensitive half of the distribution of data for steelhead/rainbow trout sensitivity to cadmium, and the chronic criterion still would not protect the listed threespine stickleback. With a data rich species such as rainbow trout, instead of defining acute criteria using a central tendency statistic such as the geometric mean of multiple test responses, using a lower statistic such as the 10th percentile would ensure that the vast majority of a sensitive, protected species (and all less sensitive species) would be protected. Available data for the stickleback indicate it may be highly sensitive to cadmium, but no threshold can be derived from existing data. Additional testing with cadmium and stickleback would be needed to suggest an alternative, quantitative approach.

California↗

USGS2021

Direct and delayed mortality of Ceriodaphnia dubia and rainbow trout following time-varying acute exposures to zinc

The potential for delayed mortality following short-term episodic pollution events was evaluated by exposing cladocerans ( Ceriodaphnia dubia ) and rainbow trout ( Oncorhynchus mykiss ) to zinc (Zn) in various 1- to 48-h and 1- to 96-h exposures, respectively, followed by transferring the exposed organisms to clean water for up to 47 h for C. dubia and up to 95 h for trout for additional observation. For C. dubia , 1-h exposures of up to 3790 µg Zn/L never resulted in mortality during the actual Zn exposures, but by 48 h, a 1-h exposure to 114 µg/L, a concentration similar to the present US national water quality acute criterion for the test water conditions, ultimately killed 70% of C. dubia . With C. dubia , the speed of action of Zn toxicity was faster for intermediate concentrations than for the highest concentrations tested. For rainbow trout, pronounced delayed mortalities by 96 h only occurred following ≥8-h exposures. For both species, ultimate mortalities from Zn exposures ≤8 h mostly presented as delayed mortalities, whereas for exposures ≥24 h, almost all ultimate mortalities presented during the actual exposure periods. With Zn, risks of delayed mortality following exposures to all concentrations tested were much greater for the more sensitive, small-bodied invertebrate ( C. dubia ) than for the less sensitive, larger-bodied fish (rainbow trout). These results, along with previous studies, show that delayed mortality is an important consideration in evaluating risks to aquatic organisms from brief, episodic exposures to some substances. Environ Toxicol Chem 2021;40:2484–2498. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Environmental Toxicology and Chemistry↗

USGS2021

Nutrient limitation of algae and macrophytes in streams: Integrating laboratory bioassays, field experiments, and field data

Successful eutrophication control strategies need to address the limiting nutrient. We conducted a battery of laboratory and in situ nutrient-limitation tests with waters collected from 9 streams in an agricultural region of the upper Snake River basin, Idaho, USA. Laboratory tests used the green alga Raphidocelis subcapitata , the macrophyte Lemna minor (duckweed) with native epiphytes, and in situ nutrient-limitation tests of periphyton were conducted with nutrient-diffusing substrates (NDS). In the duckweed/epiphyte test, P saturation occurred when concentrations reached about 100 μg/L. Chlorophyll a in epiphytic periphyton was stimulated at low P additions and by about 100 μg/L P, epiphytic periphyton chlorophyll a appeared to be P saturated. Both duckweed and epiphyte response patterns with total N were weaker but suggested a growth stimulation threshold for duckweed when total N concentrations exceeded about 300 μg/L and approached saturation at the highest N concentration tested, 1300 μg/L. Nutrient uptake by epiphytes and macrophytes removed up to 70 and 90% of the N and P, respectively. The green algae and the NDS nutrient-limitation test results were mostly congruent; N and P co-limitation was the most frequent result for both test series. Across all tests, when N:P molar ratios >30 (mass ratios >14), algae or macrophyte growth was P limited; N limitation was observed at N:P molar ratios up to 23 (mass ratios up to 10). A comparison of ambient periphyton chlorophyll a concentrations with chlorophyll a accrued on control artificial substrates in N-limited streams, suggests that total N concentrations associated with a periphyton chlorophyll a benchmark for desirable or undesirable conditions for recreation would be about 600 to 1000 μg/L total N, respectively. For P-limited streams, the corresponding benchmark concentrations were about 50 to 90 μg/L total P, respectively. Our approach of integrating controlled experiments and matched biomonitoring field surveys was cost effective and more informative than either approach alone.

Idaho↗

USGS2021

Long-term monitoring reveals convergent patterns of recovery from mining contamination across 4 western US watersheds

Long-term studies of stream ecosystems are essential for assessing restoration success because they allow researchers to quantify recovery trajectories, gauge the relative influence of episodic events, and determine the time required to achieve clean-up objectives. To quantify responses of benthic macroinvertebrate assemblages to stream remediation, we integrated results of 4 long-term (20–29 y) assessments of mining-impacted watersheds that were broadly distributed across the western US (California, Colorado, Idaho, Montana). Using a before–after control–impact (BACI) study design, we observed substantial reductions in metal concentrations and corresponding improvements of benthic assemblages following remediation. Recovery rates were relatively consistent, and streams typically recovered within 10 to 15 y after remediation was initiated (mean = 10.25 y), although episodic events changed trajectories at some sites. Differences in recovery among watersheds were likely determined by a number of factors, including the severity of contamination, effectiveness of remediation, proximity to upstream sources of colonization, and hydrologic variation. We also observed considerable variation in the rate and extent of recovery among assemblage metrics. For example, total abundance and richness recovered rapidly at most sites, but the composition of benthic macroinvertebrate assemblages remained substantially altered compared with reference sites. Using piecewise linear regression, we estimated a threshold response of Ephemeroptera, Plecoptera, and Trichoptera (EPT) species richness at ~1 cumulative criteria unit (CCU), which is the sum of the fractions of chronic water-quality criteria for metals measured, suggesting this value was protective of benthic assemblages. However, EPT richness was reduced by ~20% at 2× this CCU value, indicating that moderate exceedances of water-quality criteria could substantially affect stream biodiversity. Non-metric multidimensional scaling analyses identified common sets of species trait states across the 4 watersheds that were associated with either metal contamination or with recovering and intact reference stream assemblages. Our study illustrates the importance of long-term studies for quantifying responses to stream restoration and the usefulness of BACI designs for demonstrating cause-and-effect relationships between restoration treatments and community recovery. Because these 4 watersheds were among the most severely polluted sites in the western US, our study demonstrates the value of these investments in watershed restoration and the potential for success under the most extreme conditions.

California, Colorado, Idaho, Montana↗

USGS2020

Bioaccumulation and toxicity of cadmium, copper, nickel, and zinc and their mixtures to aquatic insect communities

We describe 2 artificial stream experiments that exposed aquatic insect communities to zinc (Zn), copper (Cu), and cadmium (year 2014) and to Zn, Cu, and nickel (year 2015). The testing strategy was to concurrently expose insect communities to single metals and mixtures. Single-metal tests were repeated to evaluate the reproducibility of the methods and year-to-year variability. Metals were strongly accumulated in sediments, periphyton, and insect (caddisfly) tissues, with the highest concentrations occurring in periphyton. Sensitive mayflies declined in metal treatments, and effect concentrations could be predicted effectively from metal concentrations in either periphyton or water. Most responses were similar in the replicated tests, but median effect concentration values for the mayfly Rhithrogena sp. varied 20-fold between the tests, emphasizing the difficulty comparing sensitivities across studies and the value of repeated testing. Relative to the single-metal responses, the toxicity of the mixtures was either approximately additive or less than additive when calculated as the product of individual responses (response addition). However, even less-than-additive relative responses were sometimes greater than responses to similar concentrations tested singly. The ternary mixtures resulted in mayfly declines at concentrations that caused no declines in the concurrent single-metal tests. When updating species-sensitivity distributions (SSDs) with these results, the mayfly responses were among the most sensitive 10th percentile of available data for all 4 metals, refuting older literature placing mayflies in the insensitive portion of metal SSDs. Testing translocated aquatic insect communities in 30-d artificial streams is an efficient approach to generate multiple species effect values under quasi-natural conditions that are relevant to natural streams.

Environmental Toxicology and Chemistry↗

USGS2020

Copper concentrations in the upper Columbia River as a limiting factor in White Sturgeon recruitment and recovery

Currently there is little natural recruitment of white sturgeon (Acipenser transmontanus) in the Upper Columbia River located in British Columbia, Canada and Washington, USA. This review of life history, physiology, and behavior of white sturgeon, along with data from recent toxicological studies, suggest that trace metals, especially Cu, affect survival and behavior of early life stage ﬁsh. Sturgeon free embryos, ﬁrst feeding embryos, and mixed feeding embryos utilize interstitial spaces between gravel. Although concentrations of Cu in the water column of the Upper Columbia River are typically less than US water quality criteria deﬁned to protect aquatic life, samples at the sediment–water interface were as large as 24 µg/L and exceed the criteria. Toxicological studies reviewed here demonstrate mortality, loss of equilibrium, and immobility at Cu concentrations of 1.5 to <16 µg/L and reduced swimming activity was documented at 0.88 to 7 μg/L. Contaminated invertebrates and slag particles provide other routes of exposure. These additional routes of exposure can cause indirect effects from starvation due to potential lack of prey items and ingestion of contaminated prey or slag particles. The lack of food in stomachs during these critical early life stages may coincide with a threshold “point of no return” at which sturgeon will be unable to survive even if food becomes available following that early time frame. These ﬁndings become especially important as work progresses to enhance white sturgeon recruitment in the Upper Columbia River. To date, decisions against including trace metals as a factor in sturgeon recovery have focused on surface‐water concentrations and measurements of lethality (LC50) to establish threshold concentrations for sturgeon sensitivity. However, information provided here suggests that measurements from the sediment–water interface and effect concentrations (EC50) be considered with white sturgeon life history characteristics. These data support minimizing Cu exposure risk to enhance a successful white sturgeon recovery effort.

Washington, British Columbia↗

USGS2020

Metal bioavailability models: Current status, lessons learned, considerations for regulatory use, and the path forward

Since the early 2000s, biotic ligand models and related constructs have been a dominant paradigm for risk assessment of aqueous metals in the environment. We critically review 1) the evidence for the mechanistic approach underlying metal bioavailability models; 2) considerations for the use and refinement of bioavailability-based toxicity models; 3) considerations for the incorporation of metal bioavailability models into environmental quality standards; and 4) some consensus recommendations for developing or applying metal bioavailability models. We note that models developed to date have been particularly challenged to accurately incorporate pH effects because they are unique with multiple possible mechanisms. As such, we doubt it is ever appropriate to lump algae/plant and animal bioavailability models; however, it is often reasonable to lump bioavailability models for animals, although aquatic insects may be an exception. Other recommendations include that data generated for model development should consider equilibrium conditions in exposure designs, including food items in combined waterborne–dietary matched chronic exposures. Some potentially important toxicity-modifying factors are currently not represented in bioavailability models and have received insufficient attention in toxicity testing. Temperature is probably of foremost importance; phosphate is likely important in plant and algae models. Acclimation may result in predictions that err on the side of protection. Striking a balance between comprehensive, mechanistically sound models and simplified approaches is a challenge. If empirical bioavailability tools such as multiple-linear regression models and look-up tables are employed in criteria, they should always be informed qualitatively and quantitatively by mechanistic models. If bioavailability models are to be used in environmental regulation, ongoing support and availability for use of the models in the public domain are essential.

Environmental Toxicology and Chemistry↗

USGS2020

Time-dependent accumulation of Cd, Co, Cu, Ni, and Zn in mayfly and caddisfly larvae in experimental streams: Metal sensitivity, uptake pathways, and mixture toxicity

Conceptual and quantitative models were developed to assess time-dependent processes in four sequential experimental stream studies that determined abundances of natural communities of mayfly and caddisfly larvae dosed with single metals (Cd, Co, Cu, Ni, Zn) or multiple metals (Cd+Zn, Co+Cu, Cu+Ni, Cu+Zn, Ni+Zn, Cd+Cu+Zn, Co+Cu+Ni, Cu+Ni+Zn). Metal mixtures contained environmentally relevant metal ratios found in mine drainage. Free metal ion concentrations, accumulation of metals by periphyton, and metal uptake by four families of aquatic insect larvae were either measured (Brachycentridae) or predicted (Ephemerellidae, Heptageniidae, Hydropsychidae) using equilibrium and biodynamic models. Toxicity functions, which included metal accumulations by larvae and metal potencies, were linked to abundances of the insect families. Model results indicated that mayflies accumulated more metal than caddisflies and the relative importance of metal uptake by larvae via dissolved or dietary pathways highly depended on metal uptake rate constants for each insect family and concentrations of metals in food and water. For solution compositions in the experimental streams, accumulations of Cd, Cu, and Zn in larvae occurred primarily through dietary uptake, whereas uptake of dissolved metal was more important for Co and Ni accumulations. Cd, Cu, and Ni were major contributors to toxicity in metal mixtures and for metal ratios examined. Our conceptual approach and quantitative results should aid in designing laboratory experiments and field studies that evaluate metal uptake pathways and metal mixture toxicity to aquatic biota.

Science of the Total Environment↗

USGS2019

Adding invasive species bio-surveillance to the U.S. Geological Survey streamgage network

The costs of invasive species in the United States alone are estimated to exceed US$100 billion per year so a critical tactic in minimizing the costs of invasive species is the development of effective, early-detection systems. To this end, we evaluated the efficacy of adding environmental (e)DNA surveillance to the U.S. Geological Survey (USGS) streamgage network, which consists of > 8,200 streamgages nationwide systemically visited by USGS hydrologic technicians. Incorporating strategic eDNA sample collection during routine streamgage visits could provide early detection surveillance of aquatic invasive species with minimal additional cost. For this evaluation, USGS hydrologic technicians collected monthly eDNA water samples, May – September 2018, from streamgages downstream of reservoirs in the Columbia River Basin thought to be vulnerable to invasive dreissenid mussel ( Dreissenidae spp.) establishment. We tested water samples for dreissenid mussel DNA and also for kokanee ( Oncorhynchus nerka ) and yellow perch ( Perca flavescens ) DNA; the two fishes were used to assess if streamgages are adequately located to provide early-detection eDNA surveillance of taxa known to be present in upstream reservoirs. No Columbia River Basin streamgage samples met our criteria for being scored as positive for dreissenid DNA. We did detect kokanee and yellow perch DNA at all streamgages downstream of reservoirs where these species are known to occur. Field collection, laboratory analyses, and personnel time required for collection of four eDNA samples at a streamgage site cost US$500 -US$600 (net). Given these results, incorporating eDNA biosurveillance into routine streamgage visits might decrease costs associated with an invasion since early detection maximizes the potential for eradication, containment, and mitigation.

Ecosphere↗

USGS2019

Scientific integrity issues in environmental toxicology and chemistry: Improving research transparency, reproducibility, and credibility

High‐profile reports of detrimental scientific practices leading to retractions in the scientific literature contribute to lack of trust in scientific experts. Although the bulk of these have been in the literature of other disciplines, environmental toxicology and chemistry are not free from problems. While we believe that egregious misconduct such as fraud, fabrication of data, or plagiarism is rare, scientific integrity is much broader than the absence of misconduct. We are more concerned with more commonly encountered and nuanced issues such as poor reliability and bias. We review a range of topics including conflicts of interests, competing interests, some particularly challenging situations, reproducibility, bias, and other attributes of ecotoxicological studies that enhance or detract from scientific credibility. Our vision of scientific integrity encourages a self‐correcting culture that promotes scientific rigor, relevant reproducible research, transparency in competing interests, methods and results, and education.

Integrated Environmental Assessment and Management↗

USGS2018

Characterizing toxicity of metal‐contaminated sediments from the Upper Columbia River, Washington, USA, to benthic invertebrates

Sediments from the Upper Columbia River, Washington, USA, are contaminated with metals from smelting operations. We conducted short‐term and long‐term tests with the midge Chironomus dilutus and the amphipod Hyalella azteca and short‐term tests with the freshwater mussel Lampsilis siliquoidea with 54 sediments from the Upper Columbia River to characterize thresholds for toxicity of metals to benthic invertebrates. Test sediments were screened for toxicity by comparisons with low‐metal reference sediments. Toxic effects on amphipods occurred primarily in sediments from the upstream (riverine) reach, and toxic effects on midges occurred in sediments from both the upstream reach and the downstream (reservoir) reach. Little toxicity was observed in mussel tests. Toxicity thresholds (20% effect concentrations [EC20s]) for metals in sediment and porewater were estimated from logistic concentration–response models. Copper (Cu) concentrations in the simultaneously extracted metal fraction of sediments and bioavailable Cu in porewater, as characterized by biotic ligand models, had consistent associations with toxicity endpoints. Concentration–response models for sediment Cu produced EC20s for 6 endpoints, with long‐term amphipod survival and reproduction being the most sensitive. A logistic regression model fitted to an endpoint sensitivity distribution for sediment Cu predicted that approximately one‐half of the sediments tested would be toxic to at least one endpoint and that approximately 20% of test sediments would be toxic to more than half of the endpoints. These results indicate that sediments from the upstream reach of the Upper Columbia River, which contain high concentrations of metals associated with slags, cause a wide range of toxic effects in laboratory tests and are likely to have adverse effects on benthic invertebrate communities.

Washington↗

USGS2018

Mercury concentrations in water and mercury and selenium concentrations in fish from Brownlee Reservoir and selected sites in the Boise and Snake Rivers, Idaho and Oregon, 2013-17

Mercury (Hg) analyses were conducted on samples of water and sport fish collected from selected sampling sites in the Boise and Snake Rivers and Brownlee Reservoir, in Idaho and Oregon, to meet National Pollution Discharge and Elimination System permit requirements for the City of Boise, Idaho, from 2013 to 2017. City of Boise personnel collected water samples from six sites in October and November of 2013, 2015 and 2017, and sampled one site in 2014 and 2016. Total Hg concentrations in unfiltered water samples ranged from 0.41 to 8.78 nanograms per liter (ng/L), with the highest value (8.78 ng/L) observed in Brownlee Reservoir in 2013. All samples were less than the U.S. Environmental Protection Agency aquatic life criterion of 12 ng/L. Individual fillets of mountain whitefish ( Prosopium williamsoni ), rainbow trout ( Oncorhynchus mykiss ), smallmouth bass ( Micropterus dolomieu ), and channel catfish ( Ictalurus punctatus ) were collected and analyzed for Hg. The tissue Hg concentrations were compared with regulatory or advisory values for wet-weight methylmercury in fish tissue. In this report, methylmercury concentrations in fish tissue are considered similar to total Hg in fish muscle tissue and are simply referred to as Hg. The 2013 average Hg concentration for smallmouth bass (0.32 mg/kg) collected at Brownlee Reservoir and for channel catfish (0.33 mg/kg) collected at the Boise River mouth, exceeded the Idaho water quality criterion (>0.3 mg/kg). The 2017 Hg concentrations in smallmouth bass from Brownlee Reservoir (geometric mean of 0.22 mg/kg) was at the Idaho Fish Consumption Advisory Program action level. Selenium (Se) interacts with Hg to reduce the health risks of Hg, such that tissues with Se-to-Hg molar ratios greater than 1 are considered to present less potential health risks for a given Hg concentration than are tissues with lower Se-to-Hg ratios. One composite fish tissue sample per site was analyzed for Se. Selenium-to-Hg molar ratios in the fish tissue samples ranged from 0.99 to 24.7.

Idaho, Oregon↗

USGS2018

Potential toxicity of dissolved metal mixtures (Cd, Cu, Pb, Zn) to early life stage white sturgeon (Acipenser transmontanus) in the Upper Columbia River, Washington, United States

The Upper Columbia River (UCR) received historical releases of smelter waste resulting in elevated metal concentrations in downstream sediments. Newly hatched white sturgeon hide within the rocky substrate at the sediment–water interface in the UCR for a few weeks before swim-up. Hiding behavior could expose them to metal contaminants, and metal toxicity could contribute to population declines in white sturgeon over the past 50 years. This study evaluates whether there is a link between the toxicity of dissolved metals across the sediment-water interface in the UCR and the survival of early life stage (ELS) white sturgeon. Toxicity of dissolved metal mixtures is evaluated using a combination of previously collected laboratory and field data and recently developed metal mixture toxicity models. The laboratory data consist of individual metal (Cd, Cu, Pb, and Zn) toxicity studies with ELS white sturgeon. The field data include the chemical composition of surface and pore water samples that were collected across the sediment–water interface in the UCR. These data are used in three metal accumulation and two response models. All models predict low toxicity in surface water, whereas effects concentrations greater than 20% are predicted for 60–72% of shallow pore water samples. The flux of dissolved metals, particularly Cu, from shallow pore water to surface water likely exposes prime ELS sturgeon habitat to toxic conditions.

Washington↗

USGS2018

Spatial and temporal trends in selenium in the upper Blackfoot River watershed, southeastern Idaho, 2001–16

Phosphate mining in southeastern Idaho has been an important economic driver for the region and State for over 100 years, but weathering of mining waste rock has also released selenium into the Blackfoot River. This report analyzes and presents data from three separate but complementary studies monitoring selenium in streams in the region. The U.S. Geological Survey (USGS), in cooperation with the Bureau of Land Management, has been collecting streamflow and water-quality samples year-round on the Blackfoot River above reservoir near Henry, Idaho, (USGS streamgage 13063000) since 2001. Over the same period, the Idaho Department of Environmental Quality (IDEQ) has collected streamflow and water-quality samples from the Blackfoot River and tributaries during spring runoff. Data collected from 2001 to 2012 during these two studies were analyzed previously. This report extends the analysis using new data collected through 2016. This report also presents the results of a joint USGS and IDEQ seepage study conducted in June 2016 in the Blackfoot River near Dry Valley. Although limited in scope, this study explored the hypothesis that unaccounted selenium loading (loading in excess of tributary inputs) in this reach could be caused by groundwater inflow. USGS dissolved selenium concentration data from streamgage 13063000 on the Blackfoot River and IDEQ data from the mainstem and mining-affected tributaries are highest shortly after peak runoff and correlate with streamflow magnitude. Although earlier analyses indicated increasing selenium concentrations from 2001 to 2012, this study shows that runoff and baseflow dissolved selenium concentrations increased and then decreased during 2001–16. High median runoff concentrations from 2005 through 2011 are associated with high snowpack and streamflow. This result suggests that more snowmelt moving through selenium-bearing waste rock leads to increased instream concentrations. The time lag between peak runoff and then peak selenium concentrations suggests that selenium mobilization may occur as snowmelt percolates through waste rock rather than by faster surface runoff. However, variability in local snow accumulation and snowmelt conditions likely affects interannual variability in selenium concentrations in the mainstem Blackfoot River and tributaries. In contrast to runoff selenium concentrations, median baseflow (August to October) dissolved selenium concentrations were highest from 2009 to 2013. Aquatic plant senescence and release of selenium is an unlikely explanation for this trend because plants are still growing during this time of year. In addition, this trend is observed during and shortly after the observed period of high snowpack. Thus, increased baseflow selenium concentrations suggest that increased selenium loading to alluvial groundwater may occur during periods of high snowmelt and manifest in later years as higher instream concentrations during baseflows when the majority of streamflow is attributable to groundwater gains. Runoff-period streamflow and selenium loads were calculated for the tributaries and mainstem Blackfoot River. Selenium loads vary from year to year with mainstem loads greater than the total tributary contributions in some years and less than tributary contributions in other years. In general, East Mill Creek usually accounted for the largest proportion of the total Blackfoot River load, and unaccounted loads (loads in excess of tributary inputs) often occurred in the vicinity of Spring Creek and Dry Valley. The latter observation led the USGS and IDEQ to conduct a seepage study to further investigate groundwater and selenium loading to the Blackfoot River near Dry Valley. The seepage study results show consistent albeit small unaccounted increases in streamflow and dissolved selenium load in the Blackfoot River near Dry Valley. Field observation of a spring to the north of the river and independent groundwater monitoring data from Dry Valley to the south of the river suggest that alluvial groundwater may discharge to the river from both sides. However, the small unaccounted selenium load measured in the June 2016 study relative to loads measured during runoff suggest that groundwater loading in this reach may occur primarily during runoff. An improved understanding of alluvial groundwater extent, gradient, hydraulic conductivity, and quality would aid in interpreting unaccounted gains and losses in selenium loads in the Blackfoot River. Finally, State of Idaho selenium water-quality criteria have recently shifted to a hierarchical fish tissue and water concentration scheme. This report summarizes existing fish tissue and water-quality data in the mainstem and offers considerations for future selenium monitoring in the Blackfoot River.

Idaho↗