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Site Specific Water Quality Objectives for Selenium in the Newport Bay Watershed: Habitat, Populations, and Protective Criteria. Earl Byron/CH2M HILL Gary Santolo/CH2M HILL Harry Ohlendorf/CH2M HILL Joseph Skorupa/USFWS Sam Luoma/USGS Theresa Presser/ USGS
Site Specific Water Quality Objectives for Selenium in the Newport Bay Watershed: Habitat, Populations, and Protective Criteria Earl Byron/CH2M HILL Gary Santolo/CH2M HILL Harry Ohlendorf/CH2M HILL Joseph Skorupa/USFWS Sam Luoma/USGS Theresa Presser/ USGS 33rd Annual SETAC Meeting November 15, 2012
Background: The Listing, TMDLs, and Need for Site-Specific Objectives • Diffuse sources of selenium (Se) in surfacing groundwater from the “Swamp of the Frogs”, San Diego Creek/Newport Bay, Orange County, CA • 303(d) listings: TMDLs for 14 toxic pollutants, including Se • EPA TMDL based on 5 µg /L Se in water: 2002 • Nitrogen Selenium Management Program: Since 2004. Stakeholders/regulators • Data and Modeling (Historical, CH2M HILL, USGS) • Selection of tissue objectives for bird eggs and fish. • Focus on the freshwater portions of the watershed. • Draft BPA, TMDL, and SSO: Tissue Objectives and Secondary Water Column Guidelines.
Dry/Wet Weather Concentrations, San Diego Creek
Background: Selenium factoids • Metalloid, chemically similar to sulfur. 4 oxidation states (-2, 0, +4, +6) mediated by microbes. Some (-2) form volatile compounds. Selenite (+4) and selenate (+6) are most common. • Abundant in marine shales and enhanced in surface soils and surface and groundwater through agriculture practices, coal, mining, and oil and gas processing. • Essential trace element (cellular redox regulation and signaling; immune system). • Reproductive toxin (substitutes for S; alters proteins; oxidative stress) • Smallest known range between deficiency and toxicity for trace elements.
Dynamic and Bioaccumulative • Rapidly taken up and converted to other forms • Low waterborne concentrations could mean low loading or high uptake (or both) • Selenium bioaccumulates and concentrates in tissues to potentially toxic levels (eggs/larvae most sensitive). • Bioaccumulation occurs primarily through dietary ingestion • EPA and Regional Boards allow for the establishment of site-specific objectives (SSOs) that are tissue-based
Translation: Tissue to water is site-specific and there is no National/State guidance. The need for modeling. • USGS adapted the San Francisco Bay Biodynamic Selenium Model to apply to the Newport Bay watershed. • Initial uptake from sediment or water = 1000x increase (bioaccumulation factor from water to microbes, plants, suspended matter) = (particulate/water ratio). Partitioning Coefficient. • Trophic transfer factors (TTFs) from plants to invertebrates or invertebrates to fish or fish to birds are in the range of < 1 to > 2 (outlier of 38) for each transfer step (tissue/food ratio) • Translation from a protective tissue level back to the required level in water has to go backward through these steps. • A hydrodynamic mixing model will eventually be needed for creeks, wetlands, and the bay to link waterborne loading to tissue levels.
Tissue-Based Risk levels • Fish eggs/embryos > 10 - 17 mg Se/kg (dw) • Fish whole body > 3 – 8.1 mg Se/kg (dw) • Bird eggs > 6 – 12 mg Se/kg (dw) • Bird Diet 3 – 6 mg Se/kg (dw)
The freshwater fish community • The drainage channels and highly modified stream channels and wetlands of the watershed are home to at least 10 species of invasive, warmwater fish; a variety of centrarchids, mosquitofish, catfish, cyprinids (no, not just carp), and a few others. No native species have been found other than striped mullet in the tidal reach of the creek, just upstream of the bay. • Many of these fish are food items for piscivorous birds that nest in Newport Bay and upstream in the wetlands (skimmers, terns, grebes).
Species of concern: Avocets, other shorebirds, waterfowl, and marine, fish-eating birds: 5 special-status species with critical habitat in the watershed and bay.
Target Species and Selenium Concentrations • Freshwater Fish • Various reproducing populations of sunfish (bluegill, green sunfish, largemouth bass)~5 – 25 mg Se/kg dw • Mosquitofish, Big Canyon Wash ~55-65 mg Se/kg dw. (Se 4+ drainage). • Each sample to be a composite of 5, similarly-sized, whole-body fish • Bird Eggs • Freshwater: Shorebirds (avocet, stilt), grebes, coots ~ 2 – 40 mg Se/kg dw • Bay: Terns, skimmers, shorebirds ~3 – 5 mg Se/kg dw • Up to 8 eggs each of 3 species per site • Analyzed as individual eggs; examined for deformity of embryos as well as chemistry.
The San Diego Creek watershed • Highly elevated sources of selenium are picked up in deeply cut drainage channels that oxidize and drain an old swamp (as mobile Se6+). • Those areas of highest concentrations offer the poorest habitat: The primary exposure and risk is in the lower watershed and upper Newport Bay where nesting birds forage in areas of elevated. • Off-channel wetlands and the headwater of one small drainage provide habitats where selenium has been chemically reduced and bioaccumulation enhanced.
Conceptual Model, Exposure Pathways, and Food-Web Relationships for Freshwater Habitats in the Newport Bay Watershed
USGS: Newport Bay Watershed Biodynamic Selenium Model Composite Source Load Mostly surfacing groundwater Composite Volume (San Diego Creek) Composite Freshwater Endmember Concentration (lower San Diego Creek and wetlands) Phytoplankton, algae, bacteria suspended particulate material and bed sediment (elemental Se, particulate organo-Se, adsorbed selenite/selenate) Dissolved species (selenate, selenite, organo-Se) Transformation Partitioning (Kd) Bioaccumulation Fish* Invertebrates Trophic transfer Piscivorous birds* Fish*, shorebirds* Effects Impaired reproduction, teratogenesis, selenosis (* = Site specific tissue objective)
Ecosystem-Scale Selenium Modeling
Birds Selenium enrichment and trophic transfer in aquatic food webs. The enrichment function (EFalgae) is equivalent to the partitioning coefficient (Kd); they represent the increase in selenium concentration between water and particulates, such as algae or sediment. (From Chapman et al., 2010).
Partitioning Coefficients (Kd) are Highly Variable Across Habitats. (Form of selenium is important) • Field measurements of selenium in water versus selenium in: • Water column particulates • Surface, soft organic sediments • Algae, plants • Field-derived Kds: • San Diego Creek: 200 – 400, (~1,000, wetlands) • Newport Bay: 200 - > 1000 • Big Canyon Wash: 4,200
Trophic transfer is less variable* • TTF = (assimilation efficiency/ingestion rate)/loss rate constant • For field data, approximated = Se in organism/Se in diet • San Diego Creek Watershed: • Particulates to invertebrates: 1 - 38 • Invertebrates to fish: 0.6 – 1.3 (1.1) • Fish to fish: ~1.1 • Fish or invertebrates to bird eggs: ~1.4 • Basic Equation: Water = [(Fish/TTFfish)/TTFinverts]/Kd • Simple multipliers
The Choice: Provisional Tissue Concentrations of Selenium Protective of Wildlife. (As annual geometric means, dry season) Based on literature and knowledge of local species. To represent true “No Effect Levels” to assure compliance with ESA and MBTA. • Bird eggs: 8 mg Se/kg dw (as single, whole eggs) • Whole body fish: 5 mg Se/kg dw (as composites of small fish)
The basis for the targets • The proposed fish tissue target of 5 µg/g dw is applicable to both fresh and saltwater fish and also serves as a protective dietary target for piscivorous birds. • USFWS staff judged the bird egg tissue target of 8 µg/g dw to lie at the upper end of the range of possible No Effect Concentrations (NECs) for mallards, and in the middle of the range of possible NECs for black-necked stilts, and therefore to be sufficiently protective of the federally listed bird species that reside or forage in the watershed. • The proposed egg concentration will be protective of aquatic-dependent birds, including the federally listed Light-footed clapper rail and California least tern, in both fresh and saltwater areas of the Newport Bay watershed. Because it is considered to be a NEC, it will not violate the Migratory Bird Treaty Act
Conclusions • The interactive stakeholder and regulator approach (NSMP) to drafting the approach to deal with the water quality exceedances for selenium in the Newport Bay watershed has proven successful. • There is a recognition that some of the areas with highest concentrations of selenium are areas of no to minimal habitat for fish or birds, therefore minimizing exposure and risk. • For the freshwater portion of the watershed, the draft BPA and TMDL fit with the draft SSOs for selenium in tissue; tied together with the USGS biodynamic model that provides translation between tissue and waterborne concentrations. • The draft SSO recommended tissue targets for bird eggs and fish will be protective of the local listed species. • Translation of the target tissue levels for the lower watershed yields waterborne Se concentrations of 5 – 13 µg/L.
References for USGS Ecosystem-Scale Selenium Modeling • Presser, T.S., and Luoma, S.N., 2010, A Methodology for Ecosystem-Scale Modeling of Selenium: Integrated Environmental Assessment and Management, v. 6, no. 4, p. 685-710 . • Luoma, S.N., and Presser, T.S., 2009, Emerging Opportunities in Management of Selenium Contamination: Environmental Science and Technology, v. 43, no. 22, p. 8483-8487. • Presser, T.S., and Luoma, S.N., 2009, Modeling of Selenium for the San Diego Creek Watershed and Newport Bay, California: U.S. Geological Survey Open-File Report 2009-1114, 48 p.
Recent publications are available on the library page of the USGS/USFWS selenium website: http://wwwrcamnl.wr.usgs.gov/Selenium/Index.html (Alternative: type into Google---USGS Se sources)