Seabirds Spew Useful Contaminant Data

To measure levels of persistent organic pollutants such as polychlorinated biphenyls (PCBs) or DDT in arctic environments, scientists often have to extract minute concentrations of chemicals from ground up fish tissue or blood. But now researchers have revisited an easier, non-invasive way to detect these contaminants: the fishy oils stored in the stomachs of several seabird species (Environ. Sci. Technol., DOI: 10.1021/es1009983). The findings also point to these oils as a major route of pollutant exposure in seabird chicks.

In the 1980s, Dee Boersma of the University of Washington, Seattle first discovered petroleum contaminants in the stomach oils of fork-tailed storm-petrels and concluded that the oils could help track the contaminants in the birds, their chicks, and the environment. But in the subsequent decades, few researchers have pursued the technique.

Seabirds, such as those storm-petrels and northern fulmars that nest in Alaska and Canada, convert a portion of their fish and crustacean diet into oils and store the fats in their glandular stomach. The birds then cough up this smelly, bright orange goo as food for themselves and their chicks.

Canadian researchers have studied fulmars and other arctic seabirds and had found that the birds distribute contaminants in marine environments. As part of a study into how the birds transport these pollutants, graduate student Karen Foster and colleagues at the University of Ottawa measured high levels of PCBs and DDT in the stomach oils of two fulmars at a study site on Devon Island in Canada. They wondered whether these elevated concentrations were typical for fulmars, in general.

After studying the oils from 10 birds nesting on St. George Island in Alaska, the researchers found similarly elevated levels of PCBs and DDT. Levels of these organochlorines were 10 times greater in the oils than in whole fish and nearly 20 times greater than in whole crustaceans. When the scientists compared a chick's exposure to pollutants based on different diets, they calculated that chicks fed stomach oils ingest about 3 times more DDT than those fed whole prey.

Sampling bird stomach oils has its advantages over traditional pollutant-monitoring methods that require the extraction of small amounts of contaminants from tissue or blood samples, Foster says. Those samples only provide a measure of a bird's overall exposure, while the oils contain data about a bird's recent diet. Also traditional methods sometimes require killing the animal, while collecting oils is simple and non-invasive: The birds voluntarily spew the smelly goo at intruders near their nests, such as researchers.

By analyzing contaminants beyond petroleum chemicals, Boersma says, the researchers have underscored the value of using seabird stomach oils to monitor pollutants. And the new study draws further attention to the problem of marine contaminants.