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Mercury Risk to Avian Reproduction in San Francisco Bay: Implications for TMDL Implementation

Explore the ecotoxicological risks of mercury on avian reproduction in San Francisco Bay, analyzing trophic pathways, bioaccumulation, and implications for TMDLs. Study species include avocets, stilts, and terns across North, Central, and South Bay regions.

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Mercury Risk to Avian Reproduction in San Francisco Bay: Implications for TMDL Implementation

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  1. Mercury Risk to Avian Reproduction in San Francisco Bay: Implications for TMDL Implementation Collin Eagles-Smith, Josh Ackerman, Terry Adelsbach, John Takekawa, Keith Miles, Steve Schwarzbach, and Tom Suchanek U. S. Fish and Wildlife Service, Environmental Contaminants Division U. S. Geological Survey, Western Ecological Research Center

  2. Mercury in San Francisco Bay-Delta Birds: Trophic Pathways, Bioaccumulation, and Ecotoxicological Risk to Avian Reproduction Hg

  3. San Francisco Bay Estuary HEMISPHERIC IMPORTANCE FOR WATERBIRDS

  4. Wildlife Sensitive to Methyl Mercury Toxicity • Central nervous system effects • Altered behavior • Impaired vision, hearing, and motor skills • Endocrine effects • Reduced breeding effort • Embryo death • Embryo deformities • Chick death Forster’s Tern Nest MeHg Reduces Reproductive Success

  5. Bird Mercury Questions • Mercury differences among species. • Spatial and temporal trends in bird and egg mercury. • Relate mercury concentrations to reproductive risk. • Fish as wildlife indicators? • Implications for TMDL implementation.

  6. Species Studied • Littoral Foragers – insects & crustaceans • American avocet • Black-necked stilt • Obligate Piscivores - fish • Forster’s tern • Caspian tern

  7. Study Sites North Bay • 3 regions • North Bay (Napa-Sonoma Marsh) • Central Bay (Eden Landing, Newark) • South Bay (Don Edwards SFB NWR) Central Bay South Bay

  8. Methods • Birds Captured • Whole blood drawn • Radiomarked & tracked • Released • Mercury Analyzed at USGS Davis Field Station Mercury Lab

  9. Methods Continued • Prey fish collected • Telemetry based • Nesting monitored

  10. Birds Captured Total Captures = 668

  11. 10 1 Blood [Hg] (ppm ww) 0.1 Forster’s tern Caspian tern Avocet Stilt 0.01 10 1 Blood [Hg] (ppm ww) 0.1 North Central South 0.01 Bird Mercury Concentrations 1. Mercury differed among species P < 0.0001 2. Mercury concentrations differed among regions P < 0.0001 3. Mercury concentrations increased over time Forster’s tern 10 Blood Hg (ppm ww) 1 0.1 4/10 5/30 5/20 5/10 4/1 4/30 4/20 Date

  12. Forster’s Tern Male Hg > Female Hg (P = 0.003) Breeding > Pre-breeding (P < 0.0001) Female Pre-breed Male Breed 10 Blood [Hg] (ppm ww) 1 0.1 North Bay Central Bay South Bay North Bay > Central Bay < South Bay (P = 0.03)

  13. What Does this Mean for Birds?Risk Factor Analysis Based on Evers et al. 2004 (common loon) & Heinz and Hoffman 2003 (mallard) Hg Concentration (ppm) Risk Category Impact Blood (ww) Eggs (dw) Low <1 <3.2 Undocumented; Minimal Effects Moderate 1–3 3.2–6.8 Potential Effects; Reduced Egg Hatchability High 3–4 6.8–8 Documented Effects: Molecular, Cellular, Behavioral, Potential Population Effects Extra High >4 >8 Documented Effects at Population Level

  14. Forster’s Tern Risk Category Female Pre-breed Male Breed 10 Extra high High Moderate Blood [Hg] (ppm ww) 1 Low 0.1 North Bay Central Bay South Bay

  15. Stilt Risk Category 10 Female, pre-breeding Male, pre-breeding Extra high Female, breeding High Moderate Blood [Hg] (ppm ww) 1 Low 0.1 North Bay Central Bay South Bay

  16. 0 20 40 60 80 100 Percent of Population at Risk Low Risk Moderate Risk High Risk Extra High Risk Percent of Population at Risk Site Specific Risk Factor: High + Extra High 0% Avocet 2% Stilt North Bay 4% Caspian tern 29% Forster’s tern 0% Avocet Stilt Central Bay 0% Forster’s tern 0% Avocet 1% Stilt 22% South Bay Caspian tern 10% 27% Forster’s tern

  17. Avocet Stilt Caspian tern Forster’s tern Low Risk Moderate Risk High Risk Extra High Risk Percent of Population at Risk Breeding Birds Only Risk Factor: High + Extra High 6% 5% 10% 58%

  18. 10 Egg [THg] (ppm dw) 1 0.1 South Bay North Bay Central Bay Mercury in Eggs Avocets Stilts Forster’s Terns Risk Category Extra High High Moderate Low

  19. Avocet Stilt Forster’s tern 100 60 40 80 0 20 Low Risk Moderate Risk High Risk Extra High Risk Percent of Population at Risk All Eggs Risk Factor: High + Extra High 0% 10% 46% Percent of Population at Risk

  20. Management & Regulatory Implications • Differences in space and habitat use • Differences in diet • Differences in prey Hg Differences in mercury exposure

  21. Telemetry Map Stilts 2005 South

  22. Telemetry Map Avocets 2005 South

  23. Telemetry Map Forster’s Terns 2005 South

  24. Forster’s Tern Diet by Colony-Estimated from colony returns-

  25. Stickleback Silverside Topsmelt Mudsucker Goby Anchovy Other Pond A1 N = 151 Pond A7 N = 546 Pond A8 N = 42 Pond A16 N = 168 Eden Landing N = 20 Newark N = 246 Napa Marsh N = 13 Forster’s Tern Diet by Colony-Estimated from colony returns-

  26. Pond A1 1 1 ) ) ww ww ppm ppm Geometric Mean Geometric Mean 0.1 0.1 Fish Mercury ( Fish Mercury ( 0.01 0.01 Goby Goby Anchovy Anchovy Topsmelt Topsmelt Silverside Silverside Stickleback Stickleback Mudsucker Mudsucker Prey Fish Hg Concentrations Pond A7 Pond A8 Pond A16 North Bay

  27. Fish vs. Egg Mercury Relationships

  28. Fish vs. Egg Mercury Relationships 3 3 3 3 ) ) ) ) ww ww ww ww ppm ppm ppm ppm 2 2 2 2 Colony Egg Mercury ( Colony Egg Mercury ( Colony Egg Mercury ( Colony Egg Mercury ( 1 1 1 1 R2 = 0.07 P =0.57 R2 = 0.04 P =0.65 0 0 0 0 0 0 0.1 0.1 0 0 0.2 0.2 0.3 0.3 0.1 0.1 0.2 0.2 Silverside Mercury ( Silverside Mercury ( ppm ppm ww ww ) ) Mudsucker Mudsucker Mercury ( Mercury ( ppm ppm ww ww ) ) 3 3 ) ) ww ww ppm ppm 2 2 Colony Egg Mercury ( Colony Egg Mercury ( 1 1 R2 = 0.19 P =0.33 R2 = 0.10 P =0.31 0 0 0 0.1 0 0.2 0.1 0.2 Stickleback Mercury (ppm ww) Goby Mercury (ppm ww)

  29. Diet-weighted Fish vs. Egg Mercury: Spatially Explicit 3.5 3.0 2.5 + + 2.0 Colony Egg Mercury (ppm ww) 1.5 1.0 0.5 + 0.0 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 Diet-weighted Fish Mercury (ppm ww)

  30. Diet-weighted Fish vs. Egg Mercury: Spatially Explicit 3.5 • Need to know bird space use • Need to know bird-specific diet • Need to know bird prey Hg concentrations R2 = 0.68 P = 0.01 3.0 2.5 2.0 Colony Egg Mercury (ppm ww) 1.5 1.0 0.5 0.0 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 Diet-weighted Fish Mercury (ppm ww)

  31. Diet-weighted Fish vs. Egg Mercury: TMDL implications 3.5 • Wildlife target exceeds LOAEL • Is wildlife target • non-protective? • Does LOAEL need refinement? • OR • Are fish inadequate indicators of avian risk? R2 = 0.68 P = 0.01 3.0 2.5 2.0 Colony Egg Mercury (ppm ww) 1.5 1.0 Avian egg LOAEL 0.5 0.0 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 Diet-weighted Fish Mercury (ppm ww) TMDL Wildlife Target

  32. Eggs as indicators of wildlife risk Fail-to-Hatch Trophic Transfer Maternal Transfer Hatch Survive Mortality (<10 d)

  33. Eggs as indicators of wildlife risk Fail-to-Hatch Trophic Transfer Maternal Transfer Hatch Mortality (<10 d) Survive

  34. Birds show high site fidelity Birds are good bioindicators of Hg at small spatial and temporal scales Birds useful for Hg monitoring Conclusions:

  35. In breeding birds Especially Forster’s terns and potentially other fish-eating birds In eggs Especially Stilts and Forster’s terns Conclusions:Current mercury levels are above toxic thresholds…

  36. Individual fish species do not adequately represent wildlife exposure. Spatially explicit data on bird habitat use, diet and prey mercury to predict exposure. Eggs are valuable tools for monitoring mercury in Bay-Delta wildlife. Conclusions:

  37. Acknowledgements • CALFED Ecosystem Restoration Program: • Carol Atkins and Donna Podger • Logistical Support: • Don Edwards SF Bay NWR (USFWS): Clyde Morris, Joy Albertson, Mendel Stewart, Joelle Buffa, Eric Mruz • Eden Landing Ecological Reserve: John Krause • Napa/Sonoma Marsh Wildlife Area: Tom Huffman, Larry Wyckoff, Carl Wilcox, Karen Taylor • Bird Mercury Project Principles: • USGS: Steve Schwarzbach, Tom Suchanek, John Takekawa, A. Keith Miles, Susan De La Cruz • US FWS: Tom Maurer, Dan Welsh • SFBBO: Cheryl Strong, Janet Hansen • PRBO Conservation Science: Nils Warnock, Mark Herzog • Field Support: • Jill Bluso, Scott Demers, Sarah Stoner-Duncan, Angela Rex, John Henderson, Joe Northrup, Brooke Hill, Kristen Dybala, Eli French, Ross Wilming, Lindsay Dembosz, Cathy Johnson, Lani Stinson, Kevin Aceituno Emily Eppinger, Mychal Truwe, River Gates, Mali Nakhai, • Lab Support: • Robin Keister, Sarah Spring, Liz Bowen

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