Geography and stage of development affect persistent organic pollutants in stranded and wild-caught harbor seal pups from central California

Persistent organic pollutants have been associated with disease susceptibility and decreased immunity in marine mammals. Concentrations of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), polybrominated diphenyl ethers (PBDEs), chlordanes (CHLDs), and hexachlorocyclohexane isomers (HCHs) were evaluated in terms of stage of development and likely exposure routes (in utero, suckling, fasting) in the blubber of 202 stranded and wild-caught, primarily young of the year (n=177), harbor seals (Phoca vitulina) in the central California coast. This is the first report of HCH concentrations in the blubber of California seals. Lipid normalized concentrations ranged from 200 to 330,000ng/g for sum PCBs, 320–1,500,000ng/g for sum DDTs, 23–63,000ng/g for sum PBDEs, 29–29,000ng/g for sum CHLDs, and 2–780ng/g for sum HCHs. The highest concentrations were observed in harbor seal pups that suckled in the wild and then lost mass during the post-weaning fast. Among the pups sampled in the wild and those released from rehabilitation, there were no differences in mass, blubber depth, or percent lipid although contaminant concentrations were significantly higher in the pups which nursed in the wild. When geographic differences were evaluated in a subset of newborn animals collected near their birth locations, the ratio of sum DDTs to sum PCBs was significantly greater in samples from an area with agricultural inputs (Monterey), than one with industrial inputs (San Francisco Bay). A principal components analysis distinguished between seals from San Francisco Bay and Monterey Bay based on specific PCB and PBDE congeners and DDT metabolites. These data illustrate the important influence of life stage, nutritional status, and location on blubber contaminant levels, and thus the need to consider these factors when interpreting single sample measurements in marine mammals. ► We measured PCBs, DDTs, PBDEs, HCHs, CHLDs and pesticides in harbor seal blubber. ► Harbor seal pups were grouped by stage of development and whether they suckled or were fed an artificial diet. ► Pups in poor body condition that suckled in the wild were the most contaminated. ► A subset of pups that did not suckle or eat artificial diet was grouped by birth location. ► Pups from San Francisco Bay had more PCBs and pups from Monterey Bay had more pesticides.