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Dietary mercury exposure to endangered California Clapper Rails in San Francisco Bay

September 15, 2014

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.

Publication Year 2015
Title Dietary mercury exposure to endangered California Clapper Rails in San Francisco Bay
DOI 10.1016/j.marpolbul.2014.07.009
Authors Michael L. Casazza, Mark A. Ricca, Cory T. Overton, John Y. Takekawa, Angela Merritt, Joshua T. Ackerman
Publication Type Article
Publication Subtype Journal Article
Series Title Marine Pollution Bulletin
Index ID 70126216
Record Source USGS Publications Warehouse
USGS Organization San Francisco Bay-Delta; Western Ecological Research Center