title: Dietary mercury exposure to endangered California Clapper Rails in San Francisco Bay.
abstract: California Clapper Rails (Rallus longirostris obsoletus) are an endangered waterbird that forage in tidal-marsh habitats that pose risks from mercury exposure. We analyzed total mercury (Hg) in six macro-invertebrate and one fish species representing Clapper Rail diets from four tidal-marshes in San Francisco Bay, California. Mercury concentrations among individual taxa ranged from lowest at Colma Creek (mean range: 0.09-0.2 μg/g dw) to highest at Cogswell (0.2-0.7), Laumeister (0.2-0.9) and Arrowhead Marshes (0.3-1.9). These spatial patterns for Hg matched patterns reported previously in Clapper Rail blood from the same four marshes. Over 25% of eastern mudsnails (Ilyanassa obsolete) and staghorn sculpin (Leptocottus armatus) exceeded dietary Hg concentrations (ww) often associated with avian reproductive impairment. Our results indicate that Hg concentrations vary considerably among tidal-marshes and diet taxa, and Hg concentrations of prey may provide an appropriate proxy for relative exposure risk for Clapper Rails.
authors: U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, CA 95620, United States. Electronic address: mike_casazza@usgs.gov.
authors: Michael L
authors: ML
authors: Casazza
authors: U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, CA 95620, United States.
authors: Mark A
authors: MA
authors: Ricca
authors: U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, CA 95620, United States.
authors: Cory T
authors: CT
authors: Overton
authors: U.S. Geological Survey, Western Ecological Research Center, San Francisco Bay Estuary Field Station, 505 Azuar Drive, Vallejo, CA 94592, United States.
authors: John Y
authors: JY
authors: Takekawa
authors: U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, CA 95620, United States.
authors: Angela M
authors: AM
authors: Merritt
authors: U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, CA 95620, United States.
authors: Joshua T
authors: JT
authors: Ackerman
mesh_terms: D000818:Animals; D061006:Bays; D001717:Birds / Q000378:metabolism*; D056727:Endangered Species; D004781:Environmental Exposure; D004784:Environmental Monitoring / Q000379:methods / Q000706:statistics & numerical data*; D004785:Environmental Pollutants / Q000097:blood*; D005399:Fishes / Q000097:blood*; D007448:Invertebrates / Q000737:chemistry*; D008628:Mercury / Q000097:blood*; D012495:San Francisco; D053833:Wetlands
chemical_list: D004785:Environmental Pollutants; D008628:Mercury
keywords: Endangered species; Hg; Invertebrate; Tidal marsh