Biogeochemical Cycling of Selenium and Mercury in Bighorn Lake, Bighorn Canyon National Recreation Area, MT and WY D. Naftz and E. Barnhart, USGS, Helena, MT; D. Krabbenhoft and S. Janssen, USGS, Middleton, WI; C. Eagles-Smith, USGS, Corvallis, OR; C. Stricker, USGS, Lakewood, CO; T. Schmidt, USGS, Ft. Collins, CO; M. Ruggles, MT FWP, Billings, MT Funding provided by: US Geological Survey and National Park Service PROBLEM ♦ Elevated Hg levels in fish tissue relative to other National Parks ♦ Potential for geogenic sources of Hg (Yellowstone National Park) ♦ Sediment mitigation actions possible in future ♦ Selenium inputs to reservoir via WY landscapes ♦ Evolving information on Hg cycling in western reservoirs ♦ New EPA chronic selenium criteria approved in late 2016 OUTLINE ♦ Limnological and riverine controls on [Hg] and [Se] ♦ Hg and Hgisotopes in fish tissue ♦ Microbial community dynamics and Hg methylation ♦ Se and C / N isotopes in fish tissue ♦ Se sources to Bighorn Lake ♦ Comparison to other reservoirs ♦ Next steps BACKGROUND Hg methylation Limnology [Hg]fish [Se]fish Se sources Other reservoirs BACKGROUND Bighorn Lake Hg advisories USEPA – 0.3 mg/kg (ww) FDA – 1.0 mg/kg (ww) – “do not eat” BACKGROUND New EPA 2016 Selenium Criteria Limnology [Hg]fish [Se]fish Se sources Other reservoirs BACKGROUND WY selenium issues Limnology [Hg]fish [Se]fish Se sources Other reservoirs LIMNOLOGY Salinity gradients Early July Late August ♦ 2015 freshet replaced by higher salinity plume ♦ 2016 has higher salinity ♦ Freshwater lens below higher salinity layer Limnology [Hg]fish [Se]fish Se sources Other reservoirs LIMNOLOGY Dissolved O2 gradients Early July Late August ♦ 2015 no inverted density gradient ♦ 2016 inverted density gradient associated with low DO areas ♦ Settling POM accumulating on top of lower density freshwater lense Limnology [Hg]fish [Se]fish Se sources Other reservoirs LIMNOLOGY pH gradients Early July Late August ♦ Low pH values in 2015 likely degradation of POM on higher salinity layer (40 m) ♦ Low pH values during 2016 support areas of POM degradation Limnology [Hg]fish [Se]fish Se sources Other reservoirs LIMNOLOGY DO gradients in side canyons ♦ Restricted circulation in side canyons ♦ Elevated levels of MeHg in side canyon sediment Limnology [Hg]fish [Se]fish Se sources Other reservoirs LIMNOLOGY Turbidity and THgsuspended Early July Late August ♦ Higher THgsuspended Turb., during July Turb., synoptic in NTU in NTU 0.1 0.1 ♦ Turbidity and 0.4 0.4 THgsuspended 1.8 1.8 generally agree 7.7 7.7 during both 32.5 32.5 synoptics 138.0 138.0 ♦ Delivery of elevated 2015 2016 THgsuspended to DISTANCE FROM YELLOWTAIL DAM, IN KM forebay Limnology [Hg]fish [Se]fish Se sources Other reservoirs LIMNOLOGY SC and Se gradients 2.0 1.8 G/L µ 1.6 1.4 1.2 1.0 0.8 0.6 Afterbay 0.4 Side channel DISSOLVED SELENIUM, IN IN SELENIUM, DISSOLVED 0.2 Upper reservoir 400 500 600 700 800 900 SPECIFIC CONDUCTANCE, IN µS/CM Limnology [Hg]fish [Se]fish Se sources Other reservoirs MERCURY IN FISH TISSUE ♦ Increasing Hg with increasing length (common) Upper ♦ reservoir Numerous samples exceed anomaly FDA “do not eat” advisory ♦ Anomalous fish concentrations in upper reservoir sites? ♦ Tailwater fishery shows lowest mercury concentrations Limnology [Hg]fish [Se]fish Se sources Other reservoirs 199Hg IN FISH TISSUE ♦ 199Hg = 199Hg(permil) / 198Hg(permil) ♦ Low 199Hg in tailwater fishery reflects less photochemical processing of the Hg ♦ Water released from Yellowtail dam (> 50 m in depth) less opportunity for photochemical processing Limnology [Hg]fish [Se]fish Se sources Other reservoirs SRBs in Sediment Samples DO gradients in side canyons Total Bactera in Sediment Sulfate Reducing Bacteria 1E+09 25000 20000 100000000 15000 10000 ♦ Known Hg 10000000 5000 Bacterial copies / 0.5 g soil g / 0.5 copies Bacterial Methylators g sediment 0.5 / copies dsrB 1000000 0 1 2 5 8 1 2 5 8 10 13 15 ♦ Elevated levels of 18 19 10 13 15 18 19 MeHg in side canyon 1_replicate sediment 15_replicate Limnology [Hg]fish [Se]fish Se sources Other reservoirs SRBs in Water Samples DO gradients in side canyons 10000 35 Total Bacteria in Water Sulfate Reducing Bacteria 30 1000 25 20 100 15 ♦ Known Hg 10 10 water of mL / copies dsrB Methylators Bacterial copies/ mL of water 5 ♦ Elevated levels of MeHg in side canyon 1 0 1 2M 1 2M 2 2M 5 1 2M 1 2 2M 5 2M 8 2M 8 2M 5 20M 5 60M 5 8 60M 10 2M 10 2M 18 2M 19 5 20M 5 60M 8 60M 10 2M 10 2M 18 2M 19 10 50M 10 12M 13 32M 18 51M 19 15A 2M 15A 10 50M 10 12M 13 32M 18 19 51M 15A 2M 15A 2 113M 2 sediment 2 113M Limnology [Hg]fish [Se]fish Se sources Other reservoirs Newly Identified Mercury Methylation Genes Sediment Water Samples • All sediment sites amplified -con 13T 2B 8B 1B 5M 5B 15A 13 8T 5T 10B 5M -con 13 19 18 15 10 8 5 2 1 • Only 18B from the water -con 18BR 18T 5M 15T 1T 19T 19B 18T 18B 10T 2T samples amplified Limnology [Hg]fish [Se]fish Se sources Other reservoirs FISH TISSUE SELENIUM Tailwater fishery is anomalous ♦ Higher [Se] at depth in reservoir is reflected in tailwater fishery ♦ Some tissue samples in tailwater exceed/approach 2016 EPA chronic criteria of 11.3 mg/kg (dw) ♦ High Kds in dam release may influence Se uptake in lower trophic levels and smaller fish in tailwater? Limnology [Hg]fish [Se]fish Se sources Other reservoirs FISH TISSUE C and N ISOTOPES You are what you eat ♦ Tailwater brown trout are a full trophic level lower than reservoir population ♦ Is the tailwater food web influenced by organic detritus released from the reservoir chemocline? ♦ Is the high insect biomass in the tailwater influenced by selenium- and organic-rich detritus from the reservoir? Limnology [Hg]fish [Se]fish Se sources Other reservoirs Se INPUTS Bighorn vs. Shoshone Rivers Bighorn River Shoshone River 2.6 Bighorn River at Kane, WY Shoshone River nr Lovell, WY /SEC 10,000 0 3 2.4 ~ 783 kg Se/yr 2.2 2.0 G/L µ Lentic Se standard 1.8 1,000 0 1.6 Lentic Se standard 1.4 TRATION, IN 1.2 ~ 3,420 kg Se/yr 1.0 DISSOLVED SELENIUM CONCEN- SELENIUM DISSOLVED MEAN DAILY DISCHARGE, IN FT IN DISCHARGE, DAILY MEAN 0.8 100 0 Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul WY 2015 WY 2016 WY 2015 WY 2016 Limnology [Hg]fish [Se]fish Se sources Other reservoirs Bighorn Lake MT Se INPUTS Shoshone River WY Areas susceptible to Se contamination gage Bighorn River gage “Areas susceptible to irrigation-induced Se contamination of water and biota” “Area where some bird eggs 300 2l., ate rileeS ate 2l., 300 contain embryotoxic concentrations of selenium” “Area or site where surface water is selenium contaminated” 0 50 km Limnology [Hg]fish [Se]fish Se sources Other reservoirs Se INPUTS Comparison to Lake Koocanusa Lake Koocanusa (Elk River only) ♦ Lake Koocanusa volume = 7 km3 ♦ Bighorn Lake volume = 1.7 km3 ♦ Elk River = High Se and minor flow contributor ♦ Bighorn River = High Se and Bighorn Lake major flow contributor (Bighorn River only) Limnology [Hg]fish [Se]fish Se sources Other reservoirs Elk:Kootenay Bighorn: Shoshone 0.37 2.42 INFLOW RATIOS 12,000 12,000 Lake Koocanusa and Bighorn Lake N = 22 N = 21 N = 87 N = 50 10,000 10,000 Elk / Kootenay Bighorn / Shoshone 8,000 8,000 6,000 6,000 4,000 4,000 2,000 2,000 MEAN ANNUAL DISCHARGE, IN CFS IN DISCHARGE, ANNUAL MEAN MEAN ANNUAL DISCHARGE, IN CFS IN DISCHARGE, ANNUAL MEAN 0 0 Limnology [Hg]fish [Se]fish Se sources Other reservoirs Se IN WATER Comparison to Lake Koocanusa 2.0 N = 33 G/L 1.5 µ N I,e SDEVLOSSID I,e N N = 56 1.0 Lake Koocanusa 0.5 2015-16 Bighorn Lake 2015-16 0.0 INDIVIDUAL SAMPLES Limnology [Hg]fish [Se]fish Se sources Other reservoirs Se IN FISH TISSUE Comparison to Lake Koocanusa Lake Koocanusa (MT FWP) Bighorn Lake and tailwater (USGS / MT FWP) 25 )YLE ONLCSUM( )YLE 20 Tailwater -- Tailwater -- 15 rown trout rown trout b DW rainbow trout trout rainbow Reservoir 10 Reservoir -- -- Reservoir Reservoir PPM , INeS HISF , INeS PPM -- -- rown trout rown trout Sauger Walleye Walleye 5 b rainbow trout trout rainbow 0 SPECIES Limnology [Hg]fish [Se]fish Se sources Other reservoirs LAKE POWELL COMPARISON Similar reservoir morphology Bighorn Lake, MT/WY Lake Powell, AZ/UT Limnology [Hg]fish [Se]fish Se sources Other reservoirs SIDE CANYON ANOXIA Bighorn Lake DO/Hg Lake Powell DO Lake Powell MeHg DISTANCE FROM YELLOWTAIL DAM, IN KM DISTANCE FROM GLEN CANYON DAM, IN KM LAKE KOOCANUSA BIGHORN LAKE ♦ Se sourced from British ♦ Se sourced from Wyoming Columbia ♦ Two major river inflows (high ♦ Two major river inflows (high selenium + high flow) Se + low flow) ♦ Estimated Se loads ~ 4,200 ♦ Modeled Se loads up to 13,000 kg/yr kg/yr ♦ [Se] in reservoir ranges from ♦ [Se] in reservoir ranges from 0.25 to 1.9 µg/L µ 0.7 to 1.2 g/L ♦ No 303 (d) listing for Se ♦ Listed under Section 303 (d) as ♦ Tailwater impacts? threatened by Se Limnology [Hg]fish [Se]fish Se sources Other reservoirs LAKE POWELL BIGHORN LAKE ♦ Long, narrow reservoir with ♦ Long, narrow reservoir with numerous side canyons some side canyons ♦ Low levels of Hg in main ♦ Low levels of Hgwater in main water channel channel ♦ Seasonal anoxia in narrow ♦ Seasonal anoxia in side canyons side canyons ♦ Higher proportion of MeHg and SRB in ♦ Elevated levels of MeHgwater in sediment sediment side canyons side canyons ♦ Hg fish advisory for lower ♦ Hg fish advisory for entire reservoir reservoir Limnology [Hg]fish [Se]fish Se sources Other reservoirs Se CONCEPTUAL MODEL Watershed inputs Reservoir transformations Afterbay Tailwater Bighorn R.