These data were compiled to study mercury and selenium concentrations in fish species and assemblages in lotic waterbodies across the Upper Colorado River Basin. Data were compiled from State and Federal agencies. This data table contains raw concentration data, as well as standardized concentrations corrected for differences based on sample type (i.e., tissue type), species-specific bioaccumulation rates (Table S1), and fish size (Table S2). The data were used in linear mixed effects models to estimate average mercury and selenium concentration in fish species and in fish assemblages, including fish total length (cm), sampling location (Sub basin name and GPS coordinates), and sampling year (Figures 2,3, and 4 from manuscript).

Working in cooperation with EPA, the USGS coordinated the collection of fish tissue for processing and analyses by the EPA Region 10 Manchester Environmental Laboratory located in Port Orchard, WA. This effort was being tied to existing operations work performed by state wildlife agencies in Idaho and Montana (Ross et al. 2018). Annually, in late August and September, the Idaho Department of Fish and Game (IDFG), the Montana Department of Fish, Wildlife and Parks (MTFWP), and the Kootenai Tribe of Idaho conduct population surveys on the Kootenai River. During the 2018 electrofishing population surveys, state wildlife agency personnel also retained collected fish for this effort. The following were key design components of fish collection in the Kootenai River: (1) Fish were caught and analyzed for selenium and mercury in multiple tissues (filet, whole body, and/or egg/ovaries) as available to assess baseline contamination/bioaccumulation in fish species between Libby Dam and downstream of Bonners Ferry, ID. (2) Fish were caught from the mainstem Kootenai River in early September 2018 and analyzed for selenium and mercury from immediately downstream of Libby Dam (tailwater), downstream of Troy, MT, downstream of the ID/MT border, and in the proximity of Shorty’s Island downstream of Bonner’s Ferry. (3) The EPA Region 10 laboratory provided in-kind support for selenium and mercury analyses for the 142 fish samples collected. EPA Region 10 also provided data and sample management support via the Scribe Project Manager (RSCC). More details of the study design are given by USEPA and USGS (2018). Results: A total of 142 fish representing 13 species were retained for tissue analysis. Eggs were obtained from two species, kokanee salmon and mountain whitefish. In kokanee salmon, eggs were found in two fish from only site KR13 (Kootenai River below Libby Dam) and ranged from 4.17 to 5.01 mg/kg selenium as dry weight (dw). Eggs were found in mountain whitefish from all sites except the most downstream site sampled, KR4 (Kootenai River near Shorty’s Island). Selenium concentrations in mountain whitefish eggs ranged from 11.6 to 24.8 mg/kg (dw). An objective of the study was to compare selenium concentrations in fish and water to USEPA nationally recommended water quality criteria for selenium. The national criteria recommend that concentrations in fish eggs not exceed 15.1 mg/kg (dw), concentrations in whole-body of fish not exceed 8.5 mg/kg dry weight, or (b) concentrations in muscle tissue not exceed 11.3 mg/kg dry weight (USEPA 2016). For eggs, 6 of the 8 mountain whitefish egg samples exceeded EPA’s recommended value. No samples exceeded the whole-body criterion component of 8.5 mg/kg dry weight and no samples exceeded the muscle criterion component of 11.3 mg/kg dry weight. References: Ross, T.J., K. McDonnell, R. Hardy, and S. Stephenson. 2018. Kootenai River resident fish mitigation: white sturgeon, burbot, native salmonid monitoring and evaluation (Annual Progress Report May 1, 2016 — April 31, 2017). BPA Project # 1988-065-00, Idaho Department of Fish and Game. Report to the Bonneville Power Administration, Environment, Fish and Wildlife, Portland, OR. 118 pp. https://www.cbfish.org. USEPA. 2016. Aquatic Life Ambient Water Quality Criterion for Selenium – Freshwater 2016. 822-R-16-006, U.S. Environmental Protection Agency. 807 pp. https://www.epa.gov/wqc/aquatic-life-criterion-selenium [Accessed February 21, 2018]. USEPA and USGS. 2018. Kootenai River Fish Tissue Study Quality Assurance Project Plan. Prepared by U.S. Environmental Protection Agency, Regions 8 and 10, and U.S. Geological Survey, Idaho Water Science Center. 28 August 2018 (Revised 01 October 2018). 41 pp.

Working in cooperation with EPA, the USGS coordinated the collection of fish tissue for processing and analyses by the EPA Region 10 Manchester Environmental Laboratory located in Port Orchard, WA. This effort was being tied to existing operations work performed by state wildlife agencies in Idaho and Montana (Ross et al. 2018). Annually, in late August and September, the Idaho Department of Fish and Game (IDFG), the Montana Department of Fish, Wildlife and Parks (MTFWP), and the Kootenai Tribe of Idaho conduct population surveys on the Kootenai River. During the 2018 electrofishing population surveys, state wildlife agency personnel also retained collected fish for this effort. The following were key design components of fish collection in the Kootenai River: (1) Fish were caught and analyzed for selenium and mercury in multiple tissues (filet, whole body, and/or egg/ovaries) as available to assess baseline contamination/bioaccumulation in fish species between Libby Dam and downstream of Bonners Ferry, ID. (2) Fish were caught from the mainstem Kootenai River in early September 2018 and analyzed for selenium and mercury from immediately downstream of Libby Dam (tailwater), downstream of Troy, MT, downstream of the ID/MT border, and in the proximity of Shorty’s Island downstream of Bonner’s Ferry. (3) The EPA Region 10 laboratory provided in-kind support for selenium and mercury analyses for the 142 fish samples collected. EPA Region 10 also provided data and sample management support via the Scribe Project Manager (RSCC). More details of the study design are given by USEPA and USGS (2018). Results: A total of 142 fish representing 13 species were retained for tissue analysis. Eggs were obtained from two species, kokanee salmon and mountain whitefish. In kokanee salmon, eggs were found in two fish from only site KR13 (Kootenai River below Libby Dam) and ranged from 4.17 to 5.01 mg/kg selenium as dry weight (dw). Eggs were found in mountain whitefish from all sites except the most downstream site sampled, KR4 (Kootenai River near Shorty’s Island). Selenium concentrations in mountain whitefish eggs ranged from 11.6 to 24.8 mg/kg (dw). An objective of the study was to compare selenium concentrations in fish and water to USEPA nationally recommended water quality criteria for selenium. The national criteria recommend that concentrations in fish eggs not exceed 15.1 mg/kg (dw), concentrations in whole-body of fish not exceed 8.5 mg/kg dry weight, or (b) concentrations in muscle tissue not exceed 11.3 mg/kg dry weight (USEPA 2016). For eggs, 6 of the 8 mountain whitefish egg samples exceeded EPA’s recommended value. No samples exceeded the whole-body criterion component of 8.5 mg/kg dry weight and no samples exceeded the muscle criterion component of 11.3 mg/kg dry weight. References: Ross, T.J., K. McDonnell, R. Hardy, and S. Stephenson. 2018. Kootenai River resident fish mitigation: white sturgeon, burbot, native salmonid monitoring and evaluation (Annual Progress Report May 1, 2016 — April 31, 2017). BPA Project # 1988-065-00, Idaho Department of Fish and Game. Report to the Bonneville Power Administration, Environment, Fish and Wildlife, Portland, OR. 118 pp. https://www.cbfish.org. USEPA. 2016. Aquatic Life Ambient Water Quality Criterion for Selenium – Freshwater 2016. 822-R-16-006, U.S. Environmental Protection Agency. 807 pp. https://www.epa.gov/wqc/aquatic-life-criterion-selenium [Accessed February 21, 2018]. USEPA and USGS. 2018. Kootenai River Fish Tissue Study Quality Assurance Project Plan. Prepared by U.S. Environmental Protection Agency, Regions 8 and 10, and U.S. Geological Survey, Idaho Water Science Center. 28 August 2018 (Revised 01 October 2018). 41 pp.

Birds (Clark’s grebe , Aechmophorus clarkii; Forster’s Tern, Sterna forsteri), fish (Peacock bass, Cichla temensis, Cichla monoculus; Pescada, Plagioscion squamosissimus) and earthworms were analyzed for selenium, total mercury, and methyl mercury c oncentration and mercury speciation. A Clark’s grebe was collected from Lake Berryessa (California, United States) in September 2012. A Forster’s Tern was collected from the San Francisco Bay Estuary (California, United States) in June 2018. Bird necropsies were performed at the U.S. Geological Survey (Dixon, CA) to obtain the following tissues: head feather, breast feather, brain, skeletal muscle, kidney, and liver. Fishes were collected in September 2018 from the Tapajós River (Brazil), which is close to artisanal gold mining areas where liquid elemental mercury is used. Fish necropsies were performed to obtain muscle and liver. Earthworms were collected in 2017-2018 from two soils (Site S1 Champ-sur-Drac, Site S2 Champ-sur-Drac; France) near the chlor-alkali plant of Champ-sur-Drac. Five endogeic and one anecic earthworm were sampled at Site S1 and five endogeic and two anecic at Site S2. Chemical analyses for total mercury and methylmercury were made at the U.S. Geological Survey Mercury Research Laboratory (Middleton, Wisconsin). Chemical analyses for total selenium were made at the U.S. Geological Survey (Menlo Park, California) and University of La Rochelle (La Rochelle, France). Mercury speciation was measured by high energy-resolution X-ray absorption fine structure (HR-XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy at beamline ID26 at the European Synchrotron Radiation Facility. The screening of selenium and mercury associated with protein extracts was measured by double affinity (AF) high performance liquid chromatography-inductively coupled plasma mass spectrometry (AF-HPLC-ICPM) at the LGC Group (Teddington, United Kingdom). ORCA, a geometry optimization platform, was used to predict the structures of mercury bound to selenium in two configurations: Hg(selenoeine)4 and Hg10(methaneselenolate)20 (Hg10(SeMe)20). There are 7 files (*.csv) provided in this product: 1) site descriptions 2) analysis descriptions, 3) HR-XANES results and chemical analyses, 4) HR-XANES spectra, 5) EXAFS data, 6) EXAFS spectrum, and 7) modeled cartesian coordinates of the mercury-selenium clusters.

Birds (Clark’s grebe , Aechmophorus clarkii; Forster’s Tern, Sterna forsteri), fish (Peacock bass, Cichla temensis, Cichla monoculus; Pescada, Plagioscion squamosissimus) and earthworms were analyzed for selenium, total mercury, and methyl mercury c oncentration and mercury speciation. A Clark’s grebe was collected from Lake Berryessa (California, United States) in September 2012. A Forster’s Tern was collected from the San Francisco Bay Estuary (California, United States) in June 2018. Bird necropsies were performed at the U.S. Geological Survey (Dixon, CA) to obtain the following tissues: head feather, breast feather, brain, skeletal muscle, kidney, and liver. Fishes were collected in September 2018 from the Tapajós River (Brazil), which is close to artisanal gold mining areas where liquid elemental mercury is used. Fish necropsies were performed to obtain muscle and liver. Earthworms were collected in 2017-2018 from two soils (Site S1 Champ-sur-Drac, Site S2 Champ-sur-Drac; France) near the chlor-alkali plant of Champ-sur-Drac. Five endogeic and one anecic earthworm were sampled at Site S1 and five endogeic and two anecic at Site S2. Chemical analyses for total mercury and methylmercury were made at the U.S. Geological Survey Mercury Research Laboratory (Middleton, Wisconsin). Chemical analyses for total selenium were made at the U.S. Geological Survey (Menlo Park, California) and University of La Rochelle (La Rochelle, France). Mercury speciation was measured by high energy-resolution X-ray absorption fine structure (HR-XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy at beamline ID26 at the European Synchrotron Radiation Facility. The screening of selenium and mercury associated with protein extracts was measured by double affinity (AF) high performance liquid chromatography-inductively coupled plasma mass spectrometry (AF-HPLC-ICPM) at the LGC Group (Teddington, United Kingdom). ORCA, a geometry optimization platform, was used to predict the structures of mercury bound to selenium in two configurations: Hg(selenoeine)4 and Hg10(methaneselenolate)20 (Hg10(SeMe)20). There are 7 files (*.csv) provided in this product: 1) site descriptions 2) analysis descriptions, 3) HR-XANES results and chemical analyses, 4) HR-XANES spectra, 5) EXAFS data, 6) EXAFS spectrum, and 7) modeled cartesian coordinates of the mercury-selenium clusters.

This dataset includes the field measurements and laboratory analyses of surface water, seston, fish tissue, and sediment samples collected from Bighorn Lake, within Bighorn Canyon National Recreation area (BICA), during high flow (July 2015) and low flow (August 2016) conditions. The study area includes 7-9 sampling sites that follow a transect spanning the entire length of the reservoir from the Bighorn and Shoshone River inflows to the afterbay and tailwater below Yellowtail dam. Multiple samples were collected at each sampling site and usually included the top 2 cm of sediment at the sediment/water interface, 2 meters above the sediment/water interface, and 2 meters below the reservoir surface. Microbial samples were collected from the water column and sediment samples using sterile techniques and placed on dry ice for laboratory DNA analysis. The samples were analyzed with qPCR and high-throughput DNA sequencing analysis. The qPCR data are archived in the National Center for Biotechnology Information (NCBI) database at: https://www.ncbi.nlm.nih.gov/guide/all/. Water-quality sonde field measurements included specific conductivity, temperature, pH, dissolved oxygen, fluorescent dissolved organic matter, chlorophyll, and turbidity. These field measurements were collected at 16-18 sites at approximately 30 cm increments from the reservoir surface to the reservoir bottom. Discrete water-quality samples that were analyzed for various constituents including selenium and mercury by the U.S. Geological Survey are archived in the National Water Information System (NWIS) database at: https://maps.waterdata.usgs.gov/mapper/index.html. Fish samples were collected during May and June 2015 from throughout Bighorn Lake and in the tailwater below Yellowtail dam and assayed for total mercury, total selenium, and mercury/carbon/nitrogen isotopes.

This dataset includes the field measurements and laboratory analyses of surface water, seston, fish tissue, and sediment samples collected from Bighorn Lake, within Bighorn Canyon National Recreation area (BICA), during high flow (July 2015) and low flow (August 2016) conditions. The study area includes 7-9 sampling sites that follow a transect spanning the entire length of the reservoir from the Bighorn and Shoshone River inflows to the afterbay and tailwater below Yellowtail dam. Multiple samples were collected at each sampling site and usually included the top 2 cm of sediment at the sediment/water interface, 2 meters above the sediment/water interface, and 2 meters below the reservoir surface. Microbial samples were collected from the water column and sediment samples using sterile techniques and placed on dry ice for laboratory DNA analysis. The samples were analyzed with qPCR and high-throughput DNA sequencing analysis. The qPCR data are archived in the National Center for Biotechnology Information (NCBI) database at: https://www.ncbi.nlm.nih.gov/guide/all/. Water-quality sonde field measurements included specific conductivity, temperature, pH, dissolved oxygen, fluorescent dissolved organic matter, chlorophyll, and turbidity. These field measurements were collected at 16-18 sites at approximately 30 cm increments from the reservoir surface to the reservoir bottom. Discrete water-quality samples that were analyzed for various constituents including selenium and mercury by the U.S. Geological Survey are archived in the National Water Information System (NWIS) database at: https://maps.waterdata.usgs.gov/mapper/index.html. Fish samples were collected during May and June 2015 from throughout Bighorn Lake and in the tailwater below Yellowtail dam and assayed for total mercury, total selenium, and mercury/carbon/nitrogen isotopes.

These metadata provide data used to examine mercury and selenium concentrations in eggs of birds breeding in wetlands of the Great Salt Lake ecosystem, Utah, particularly at Bear River Migratory Bird Refuge. Eggs were salvaged during 2010 - 2012 and include 33 species of birds. These data support the following publication: Ackerman, JT, MP Herzog, CA Hartman, J Isanhart, G Herring, S Vaughn, J Cavitt, CA Eagles-Smith, H Browers, C Cline, and J Vest. 2015. Mercury and selenium contamination in waterbird eggs and risk to avian reproduction at Great Salt Lake, Utah: U.S. Geological Survey Open-File Report 2015-1020, 178 pp. http://doi.org/10.3133/ofr20151020

These metadata provide data used to examine mercury and selenium concentrations in eggs of birds breeding in wetlands of the Great Salt Lake ecosystem, Utah, particularly at Bear River Migratory Bird Refuge. Eggs were salvaged during 2010 - 2012 and include 33 species of birds. These data support the following publication: Ackerman, JT, MP Herzog, CA Hartman, J Isanhart, G Herring, S Vaughn, J Cavitt, CA Eagles-Smith, H Browers, C Cline, and J Vest. 2015. Mercury and selenium contamination in waterbird eggs and risk to avian reproduction at Great Salt Lake, Utah: U.S. Geological Survey Open-File Report 2015-1020, 178 pp. http://doi.org/10.3133/ofr20151020

Mercury is a globally distributed pollutant that threatens human and ecosystem health. Even protected areas, such as national parks, are subjected to mercury contamination because it is delivered via atmospheric deposition, often after long-range transport. In aquatic ecosystems, certain environmental conditions can promote microbial processes that convert inorganic mercury to an organic form (methylmercury). Methylmercury biomagnifies through food webs and is a potent neurotoxicant and endocrine disruptor. This dataset contains data on the length, mass, and muscle total mercury concentration of Brown Trout (Salmo trutta) and Rainbow Trout (Oncorhynchus mykiss) collected from the Colorado River in Glen Canyon National Recreation Area (GLCA) and Grand Canyon National Park (GRCA), and Bright Angel Creek in GRCA.