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

Mar Pollut Bull. 2014 Sep 15;86(1-2):254-260. doi: 10.1016/j.marpolbul.2014.07.009. Epub 2014 Jul 25.


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.

Keywords: Endangered species; Hg; Invertebrate; Tidal marsh.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Bays
  • Birds / metabolism*
  • Endangered Species*
  • Environmental Exposure*
  • Environmental Monitoring / methods
  • Environmental Monitoring / statistics & numerical data*
  • Environmental Pollutants / blood*
  • Fishes / blood*
  • Invertebrates / chemistry*
  • Mercury / blood*
  • San Francisco
  • Wetlands


  • Environmental Pollutants
  • Mercury