Due to declining water levels and increasing salinity in the Salton Sea which may increase the hazards to wildlife, the U.S. Geological Survey and U.S. Bureau of Reclamation are re-evaluating selenium concentrations in the region. As part of this work, selenium concentrations in water and sediment samples and selected other inorganic constituents were compiled from published reports, public databases, and unpublished archives into a tabulated spreadsheet. This spreadsheet represents a rapid synthesis of available data on selenium concentrations in water and sediment in the region surrounding the Salton Sea, however it does not include all data ever published in the region. Additionally, the data compilation was done with an emphasis on selenium concentrations measured after 2005, therefore earlier selenium data may be under-represented.

Due to declining water levels and increasing salinity in the Salton Sea which may increase the hazards to wildlife, the U.S. Geological Survey and U.S. Bureau of Reclamation are re-evaluating selenium concentrations in the region. As part of this work, selenium concentrations in water and sediment samples and selected other inorganic constituents were compiled from published reports, public databases, and unpublished archives into a tabulated spreadsheet. This spreadsheet represents a rapid synthesis of available data on selenium concentrations in water and sediment in the region surrounding the Salton Sea, however it does not include all data ever published in the region. Additionally, the data compilation was done with an emphasis on selenium concentrations measured after 2005, therefore earlier selenium data may be under-represented.

Estuaries provide critical habitat for a vast array of fish and wildlife but are also a nexus for core economic activities that mobilize and concentrate contaminants that can threaten aquatic species. Selenium (Se), an essential element and potent reproductive toxin, is enriched in parts of the San Francisco Estuary (SFE) to levels known to cause toxicity, yet the risk of Se to species that inhabit the SFE is not well understood. We quantified Se concentrations in muscle, liver, and ovary of the demersal cyprinid Sacramento Splittail from six regions in the SFE at three time points (fall 2010-11, spring 2017) to evaluate Se exposure risk. Here we report fish morphological attributes, total selenium concentrations in fish boneless skinless muscle, liver, and ovary, as well as carbon, nitrogen and sulfur stable isotope values and elemental mass concentrations in fish muscle.

Yuma Ridgway’s rail (Rallus obsoletus yumanensis, hereafter, rail) are an endangered species for which patches of emergent marsh within the Salton Sea watershed comprise a substantial portion of habitat for the species’ disjointed range in the southwestern United States. These areas of emergent marsh include: 1) marshes managed by federal (particularly the U.S. Fish and Wildlife Service’s Sonny Bono Salton Sea National Wildlife Refuge (SBSSNWR), state (California Department of Fish and Wildlife), and local (Imperial Irrigation District) resource agencies that are sustained by direct deliveries of Colorado River water; and 2) unmanaged marshes sustained by agricultural drainage water. Management of rail habitat in this arid environment is complicated by increasingly limited availability of unimpaired freshwater owing by recent water management decisions associated with the Quantification Settlement Agreement, and risks posed by potentially harmful concentrations of selenium (Se) found in agricultural drainage water that can readily bioaccumulate in aquatic food webs. To provide timely science for managers, the selenium concentrations in this data release are the basis for summary statistics reported in Ricca et al. 2022. These data comprise selenium concentrations and associated locations and dates of the following matrices sampled to describe pathways of selenium exposure to rails occupying managed and unmanaged marshes: 1) unfiltered surface water, midge larvae (Chironomidae), water boatmen (Corixidae), mosquitofish (Gambusia spp.) and crayfish (Astacidae). Selenium samples were collected from 15 fixed sampling points each in managed and unmanaged marshes during late February, April, and June of 2016, which corresponded to rail pre-nesting, nesting, and fledgling reproductive life-stages, respectively. Two areas within the two treatment types (managed vs. unmanaged marsh) were of particular interest to help assess risks associated with changing Sea dynamics and different water management strategies: 1) a large unmanaged marsh (Morton Bay) unintentionally created in approximately 2008 when it became separated from the Salton Sea as water inflows began to drop and a berm formed from accumulated sediment; and 2) a restored marsh (HZ-9A) managed by the SBSSNWR, which is currently supplied with Colorado River water, but may be sustained in the future by a blend of clean (that is, low Se) Colorado River and agricultural drainage water with higher Se from the Alamo River.

The trace element selenium is an essential element with a narrow window between concentrations needed to support life and those that cause toxicity to egg laying organisms. Selenium bioaccumulation in aquatic organisms is primarily the result of trophic transfer through food webs and is poorly predicted by dissolved concentrations in freshwater bodies. To better understand the hydrologic and biological dynamics that control selenium accumulation into fishes of the Lower Gunnison River Basin (Colorado), ecosystem scale selenium accumulation models were developed from data collected between June 2015 and October 2016.

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.

This dataset includes analyses of selenium (Se) in water, sediment, periphyton, and benthic invertebrate and fish tissues from the Kootenai River in Idaho and Montana. The samples were collected as part of a study intended to evaluate selenium distribution and bioaccumulation in the aquatic food webs of the Kootenai River. Version 1.0 of this dataset includes complete food web sample results from our first three semi-annual sampling events (fall 2020, spring 2021, and fall 2021), in addition to more limited data from September 2018-2023 (mainly water sample results). Samples were collected from four sites on the Kootenai River between Libby Dam, Montana, and the border between Idaho, USA, and British Columbia, Canada. Sites were located at about 1, 81, 105, and 185 kilometers (km) downstream from Libby Dam. An additional comparison sampling site was on Lake Creek, near Troy, Montana. The water samples were analyzed for dissolved Se and Se species, including selenite, selenate, selenocyanate, methylseleninic acid, selenomethionine, and unknown Se species. Sediment samples were collected by scooping from depositional areas in shallow, quiescent water near the river edge. Sediment samples were sieved (63 micron pore size Nitex fabric) and analyzed for Se. Three types of periphyton and suspended particulates were sampled: periphyton scraped from rocks (PRS), periphyton grown on glass microscope slides (PSL), and suspended particulate material on flow-through filters (SPM). For invertebrates, whole-body tissues were analyzed from 43 distinct benthic invertebrate taxa, and multiple tissues were additionally analyzed for one taxon, the western pearlshell mussel, Margaritifera falcata. Five fish species were targeted for repeat sampling: mountain whitefish (Prosopium williamsoni), rainbow trout (Oncorhynchus mykiss), slimy sculpin (Cottus cognatus), redside shiner (Richardsonius balteatus), and northern pikeminnow (Ptychocheilus oregonensis). Occasional samples were also obtained from 4 additional species: kokanee (Oncorhynchus nerka), brown trout (Salmo trutta), longnose sucker (Catostomus catostomus), and largescale sucker (Catostomus macrocheilus). Fish were sometimes analyzed for whole body selenium concentrations, or dissected for separate analyses of muscle, liver, and egg-ovary tissues, and the carcass (everything leftover after the other tissues were removed). The specific tissue samples removed and analyzed varied by the sex and size of the fish, sampling event, and specific objectives. The total sample counts included in Version 1.0 of this dataset are 292 water sample results from 83 water samples, 27 sediment results, 114 periphyton results, 343 benthic invertebrate results, and 1,448 fish tissue results from 524 individual fish. Most analyses in the present dataset were for selenium with some additional analyses of mercury (Hg). Samples were collected and processed in collaboration with personnel from the Montana Fish, Wildlife, and Parks Department (MTFWP), Idaho Department of Fish and Game (IDFG), and the Kootenai Tribe of Idaho (KTOI). Laboratory analyses of water samples for Se were performed by Brooks Applied Laboratory, Seattle, WA. Laboratory analyses of solid phase samples were analyzed by the U.S. Geological Survey (USGS) Menlo (now Moffett) Selenium Laboratory, Menlo Park, CA; the U.S. Environmental Protection Agency’s (USEPA) Region 10 Manchester Environmental Laboratory, Manchester, WA; and by ALS Laboratory, Kelso, WA. Funding for this work was provided by a congressional appropriation to the USGS for mining-associated pollution monitoring in U.S. and British Columbia, Canada, transboundary watersheds.

This Data Release presents multi-agency data for selenium concentrations in ecosystem media that includes water column, suspended particulate material, zooplankton, invertebrates, and fish. Because the data are compiled from multiple sources, the significant figures used to report contaminant concentrations and other metrics may not be internally consistent. These data will serve as the basis for ecosystem-scale modeling of Lake Koocanusa, a bi-national reservoir in Montana and British Columbia. Spreadsheets are ordered in a food-web format to facilitate modeling that emphasizes spatially and temporally paired data. Selenium concentrations are species-specific for fish and taxa-specific for invertebrates to address required specificity for biodynamic dietary modeling. Phytoplankton, zooplankton, and invertebrate densities or biomass are compiled, in addition to fish catches, to help elucidate productivity and identify which groups, taxa, or species are abundant on a seasonal basis. For water quality context, the historical record of selenium concentrations is given, with emphasis on the primary selenium loading site near where the Elk River enters Lake Koocanusa. Spreadsheets with the term "annex" in their file name address a competing toxin, mercury, for fish. Recent high frequency monitoring of selenium concentrations at the international border and at a gaging station below Libby Dam provide a perspective on future selenium data availability. Methodologies are described as federal, provincial, and state agencies transition to a consistent set of protocols to ensure consistency in monitoring for locations on both sides of the border.

This Data Release presents multi-agency data for selenium concentrations in ecosystem media that includes water column, suspended particulate material, zooplankton, invertebrates, and fish. Because the data are compiled from multiple sources, the significant figures used to report contaminant concentrations and other metrics may not be internally consistent. These data will serve as the basis for ecosystem-scale modeling of Lake Koocanusa, a bi-national reservoir in Montana and British Columbia. Spreadsheets are ordered in a food-web format to facilitate modeling that emphasizes spatially and temporally paired data. Selenium concentrations are species-specific for fish and taxa-specific for invertebrates to address required specificity for biodynamic dietary modeling. Phytoplankton, zooplankton, and invertebrate densities or biomass are compiled, in addition to fish catches, to help elucidate productivity and identify which groups, taxa, or species are abundant on a seasonal basis. For water quality context, the historical record of selenium concentrations is given, with emphasis on the primary selenium loading site near where the Elk River enters Lake Koocanusa. Spreadsheets with the term "annex" in their file name address a competing toxin, mercury, for fish. Recent high frequency monitoring of selenium concentrations at the international border and at a gaging station below Libby Dam provide a perspective on future selenium data availability. Methodologies are described as federal, provincial, and state agencies transition to a consistent set of protocols to ensure consistency in monitoring for locations on both sides of the border.