Publication Date

Spring 2012

Degree Type


Degree Name

Master of Science (MS)


Moss Landing Marine Laboratories


James T. Harvey


harbor seals, mercury, Phoca vitulina, red pelage, San Francisco Bay, selenium

Subject Areas

Biology; Toxicology


San Francisco Bay (SFB) is the largest estuary on the west coast of the United States. It provides habitat for many species, although is heavily urbanized with a history of selenium (Se) and mercury (Hg) contamination. Harbor seals (Phoca vitulina) are good indicators of the health of SFB because they are long–lived, upper–level trophic consumers, and present in the estuary year–round. The objective of this study was to examine the role of Se and Hg contamination on the health of harbor seals in this region, and the role of Se in the development of a red pelage. Between 2009 and 2011, free–ranging seals (n = 146) were sampled at three sites off central California. Harbor seals from SFB and Tomales Bay had greater total Hg (THg) and lesser Se concentrations in hair than seals from Elkhorn Slough. Differences in THg concentrations with location were likely the result of historic gold and Hg mining. Lesser Se concentrations in seals from SFB and Tomales Bay may indicate that these seals have a greater physiologic requirement for Se due to increased Hg exposure. Concentrations of THg measured in this study may be great enough to negatively impact the health of harbor seals, however, seals in SFB did not appear to suffer from chronic Se toxicosis. The development of a red pelage may be the result of external iron deposition because of increased dependence on benthic prey and does not appear to have any short-term health implications.