Contaminant Loads And Hematological Correlates In The Harbor Seal (Phoca vitulina) Of San Francisco Bay, California

Abstract

An expanding body of research indicates that exposure to contaminants may impact marine mammal health, thus possibly contributing to population declines. The harbor seal population of the San Francisco Bay (SFB), California, has suffered habitat loss and degradation, including decades of environmental contamination. To explore the possibility of contaminant-induced health alterations in this population, blood levels of polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (DDE), and polybrominated diphenyl ethers (PBDEs) were quantified in free-ranging seals; relationships between contaminant exposure and several key hematological parameters were examined; and PCB levels in the present study were compared with levels determined in SFB seals a decade earlier. PCB residues in harbor seal blood decreased during the past decade, but remained at levels great enough that adverse reproductive and immunological effects might be expected. Main results included a positive association between leukocyte counts and PBDEs, PCBs, and DDE in seals, and an inverse relationship between red blood cell count and PBDEs. Although not necessarily pathologic, these responses may serve as sentinel indications of contaminant-induced alterations in harbor seals of SFB, which, in individuals with relatively high contaminant burdens, might include increased rates of infection and anemia.We thank staff, students, and volunteers from Moss Landing Marine Laboratories, the Richmond Bridge Harbor Seal Survey/San Francisco State University, and the Marine Mammal Center for assistance with seal capture and handling. We gratefully acknowledge Judy Lawrence (Marine Mammal Center) for running CBCs and serum chemistries. D. Anderson, B. Sacks, and two anonymous reviewers provided helpful critiques of the article. This project was supported in part by grants to J. Neale from the University of California Marine Council (02 T CEQI 03 0104) and the NIH (5 T32 ES07059-25 Traineeship in Environmental Toxicology).