Much is known about the transport and fate of oil spilled into the sea and its toxicity to exposed wildlife. Previously, however, there has been no way to quantify the probability that polar bears dispersed over the seascape would be exposed to spilled oil. Polar bears, the apical predator of the Arctic, are widely dispersed near the continental shelves of the Arctic Ocean, an area also undergoing considerable hydrocarbon exploration and development. We used 15,308 satellite locations from 194 radiocollared polar bears to estimate the probability that polar bears could be exposed to hypothetical oil spills. Simulated oil spill footprints for September and October, the times during which we hypothesized effects of an oil-spill would be worst, were estimated using real wind and current data collected between 1980 and 1996. Numbers of bears potentially oiled by a hypothetical 5912 barrel spill (the largest spill thought probable from a pipeline breach) ranged from 0 to 27 polar bears for September open water conditions, and from 0 to 74 polar bears in October mixed ice conditions. Methods described here are broadly applicable to other dispersed marine wildlife.
Amstrup, S. C., G. M. Durner, T. L. McDonald, and W. R. Johnson. 2006. Estimating potential effects of hypothetical oil spills on polar bears. U.S. Geological Survey final report to the U.S. Minerals Management Service. U.S. Geological Survey, Alaska Science Center, Anchorage, Alaska. March 2006. 56 pp.
The study of recalcitrant organochlorine (OC) contaminants in the adipose tissues of polar bears (Ursus maritimus) report a wide range in concentrations. This variation may indicate possible differences in feeding ecology and biomagnification of OCs among bears in different regions and among individual polar bears. Although polar bears are top carnivores in the arctic marine ecosystem, concentrations of OCs in their adipose tissue do not always exceed those of their prey. Concentrations of many OCs similar to those in polar bears have been reported in some ringed seals (Phoca hispida), walruses (Odobenus rosmarus), and beluga whales (Delphinapterus leucas). This absence of OC biomagnification between polar bears and their prey is partly explained by the ability of polar bears to biotransform and excrete bioaccumulative compounds that many other marine mammals cannot as easily eliminate. OC concentrations among polar bears may vary with the age, sex, body condition, location of capture, or lipid composition of tissues, but these factors do not fully explain the large range in concentrations among individuals. This may in part be due to differences in diet related to the availability and use of lower trophic level prey. OC biomagnification factors in the ringed seal to polar bear food chain vary by region, further suggesting variation in polar bear diet across the North American Arctic.
We are examining the relationship to trophic level, as measured with nitrogen isotopes in polar bear blood, with PCBs and OC pesticides including six individual congeners all found at high concentrations in polar bear adipose tissue and their prey. We are also considering the application of “congener profile” to help discern trophic relationships. We will assess the influence of numerous biological factors and how they, independently or via interactions may explain the variability observed in OC concentrations in the southern Beaufort Sea population of polar bears.
Collaborating with Todd O'Hara, Associate Professor, Wildlife Toxicology, Institute of Arctic Biology,
University of Alaska Fairbanks, Wildlife Toxicology Laboratory (WTL), Fairbanks, Alaska - INBRE (IDeA Network Of Biomedical Research Excellence)
Persistent organohalogen compounds (OHCs) have been found throughout the Alaskan arctic marine food web. Although the use of some biologically hazardous chemicals has been restricted and banned in many industrialized nations, potentially harmful organic compounds persist and move across the globe. Polychlorinated biphenyls (PCBs) are a mixture of industrial chemicals with similar structures but various properties and toxicities used worldwide in electrical equipment as flame-retardants, plasticizers in waxes, and in paper manufacturing. PCBs continue to be released into the environment from electrical equipment, landfill sites, and contaminated sediments. Recently, perfluorinated organics (PFAs) used in stain repellants, and polybrominated diphenyl ethers (PBDEs) have been detected at increasingly high levels in the Arctic.
OHCs are highly lipophillic and resistant to biotransformation. They persist in the food chain, and frequently bioaccumulate in lipid rich adipose tissue. Therefore, many OHCs are found at particularly high levels in the arctic, where they biomagnify in the marine ecosystem due to the lipid-rich diets and large fat reserves of arctic marine mammals. Native people in the Canadian Arctic, who consume lipid-rich traditional foods, have been documented with greater concentrations of PCBs in their tissues than populations elsewhere in Canada and the United States.
We are examining OHC concentrations of both subcutaneous fat and whole blood from free-ranging polar bears sampled along Alaska’s Beaufort Sea coast, and are analyzing 151 OHCs as well as several summed groups of contaminants. We are also analyzing both blood and subcutaneous adipose tissue for PBDEs. These data will contribute to spatial and temporal trends assessments of OHCs and help understand potential risks to polar bear health. By comparing OHC concentrations in subcutaneous fat and whole blood, we can determine if the burden of contaminants in one tissue can be used to predict concentrations in the other. Information on how contaminant concentrations differ between polar bear fat and blood has important implications for continued monitoring and assessment of adverse health effects.
Collaborating with Todd O'Hara, Associate Professor, Wildlife Toxicology, Institute of Arctic Biology,
University of Alaska Fairbanks, Wildlife Toxicology Laboratory (WTL), Fairbanks, Alaska - INBRE (IDeA Network Of Biomedical Research Excellence) |
