Differential changes of fat-soluble vitamins and pollutants during lactation in northern elephant seal mother-pup pairs.

We investigated the changes of vitamins A and E as well as PCBs and DDTs during lactation in northern elephant seal (Mirounga angustirostris) mother-pup pairs. On average, milk vitamin A concentrations were 6 times higher during late lactation than during early lactation, a pattern that differs dramatically from terrestrial mammals. Vitamin A concentrations also significantly increased in the inner blubber throughout lactation, whereas they remained constant in the outer blubber. Similar dynamics were observed for PCBs and DDTs in maternal blubber and milk. Blubber appears to be an important storage site for vitamin A and organochlorines in seals and a direct transfer of those molecules to the mammary gland may occur. The dynamics of vitamin A, PCBs and DDTs differed from those of vitamin E. There was a significant drop in milk vitamin E concentrations between early and late lactation, which is the usual pattern observed in terrestrial mammals. The dynamics of vitamin E in the blubber layers also differed from those of vitamin A, suggesting different mechanisms of mobilization and transfer into the milk.

Mobilization of PCBs from blubber to blood in northern elephant seals (Mirounga angustirostris) during the post-weaning fast.

Northern elephant seals (Mirounga angustirostris) are characterized by extended fasting during which they rely entirely on their own body reserves. During fasts, lipids are mobilized from blubber to match the energy requirements of the animal. This transfer frees toxic fat-soluble pollutants into the blood circulation, which may exert adverse health effects, especially in young and developing animals. We investigated the dynamics of mobilization of polychlorinated biphenyls (PCBs) from the blubber of northern elephant seal pups during the post-weaning fast. Longitudinal samples of blubber and serum were collected from free-ranging animals throughout the fast at Año Nuevo, California. Blubber biopsies were separated into inner and outer layers. The PCB profiles of blubber and serum consisted mainly of penta- (PCB-101, -110, -118), hexa- (PCB-138, -153) and hepta- (PCB-180, -183, -187) chlorobiphenyls, which accounted for almost 90% of the total PCB burden. Total PCB concentrations in inner blubber increased significantly between early and late fasting (563.6+/-162.0 microg/kg lipids at early versus 911.6+/-513.1 microg/kg lipids at late fasting) whereas they remained fairly constant in outer blubber (572.6+/-134.8 microg/kg lipids at early versus 659.2+/-158.8 microg/kg lipids at late fasting). A corresponding rise of PCB concentrations was observed in serum during the second half of the fast (3.8+/-1.1 microg/l serum at early versus 7.2+/-0.9 microg/l at late fasting). The longitudinal changes in circulating total PCBs could not be explained by the changes in serum lipid fractions (cholesterol, phospholipids, triacylglycerols and free fatty acids). The increases in total PCB concentrations in inner blubber and serum were more pronounced in leaner animals, which suggests that they might be more at risk to potential toxic effects.

PCBs and DDT in the serum of juvenile California sea lions: associations with vitamins A and E and thyroid hormones.

Top-trophic predators like California sea lions bioaccumulate high levels of persistent fat-soluble pollutants that may provoke physiological impairments such as endocrine or vitamins A and E disruption. We measured circulating levels of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) in 12 healthy juvenile California sea lions captured on Año Nuevo Island, California, in 2002. We investigated the relationship between the contamination by PCBs and DDT and the circulating levels of vitamins A and E and thyroid hormones (thyroxine, T4 and triiodothyronine, T3). Serum concentrations of total PCBs (sigmaPCBs) and total DDT were 14 +/- 9 mg/kg and 28 +/- 19 mg/kg lipid weight, respectively. PCB toxic equivalents (sigmaPCB TEQs) were 320 +/- 170 ng/kg lipid weight. Concentrations of sigmaPCBs and sigmaPCB TEQs in serum lipids were negatively correlated (p < 0.05) with serum vitamin A and T3, potentially reflecting PCB-related toxicity. A slight but not significant negative correlation (p < 0.1) was observed between serum T4 and the levels of sigmaPCBs and sigmaPCB TEQs. Conversely, no relationship was evident between the contaminant concentrations and vitamin E (p > 0.1). As juvenile California sea lions are useful sentinels of coastal contamination, the high levels encountered in their serum is cause for concern about the ecosystem health of the area.

Polychlorinated biphenyls, dioxins, and furans in weaned, free-ranging northern elephant seal pups from central California, USA.

The aim of this study was to measure persistent organic pollutants in northern elephant seals ([NES], Mirounga angustirotris). We obtained blubber biopsy samples from six healthy, newly weaned NES pups from Año Nuevo, California (USA). Contaminant levels were lower than those of other pinnipeds studied on the west coast of North America. Blubber concentrations of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans averaged 700 +/- 130 microg/kg, 32 +/- 23 ng/kg, and 17 +/- 5 ng/kg (lipid wt), respectively. These contaminants originate from transplacental transfer and from maternal milk, which, in turn, reflect contaminants acquired by the mother from prey during long-distance foraging trips in the northeastern Pacific Ocean. The PCB profile in the blubber of NES pups mainly was composed of penta-, hexa-, and hepta-chlorobiphenyls, possibly reflecting the deep-sea nature of the mother's diet. Our results suggest that NES pups, in contrast to pups of other pinnipeds in the eastern Pacific Ocean, are exposed to low levels of persistent organic pollutants, reflecting an open ocean signal.