Stephanie Pappas, LiveScience Senior Writer
The best tools for tracking how well pollution-reduction laws are working may be seabirds.
Seabirds, including pelicans, gulls and terns, are at the top of the food chain, and they absorb the toxins andpollutants contained in the fish they eat, researchers write in the May 3 issue of the journal Science. And because seabirds forage over wide areas of oceans but come back to one spot each year to breed, they provide scientists with a one-stop-shop to sample from a broad geographic region.
"They essentially go out much of the year onto the ocean, and they sample for you," said John Elliott, of Environment Canada, who penned the piece with University of Manitoba researcher Kyle Elliott. "As they're feeding, they're exposed to contaminants, particularly the bioaccumulative ones that we're most interested in."
Bioaccumulative pollutants build up in biological tissue over time and can be passed down in eggs or milk, in the case of mammals. Perhaps the most famous example is DDT, an insecticide now banned for agricultural use because it thins the eggshells of birds.
Seabird toxin monitoring is not lethal to birds; scientists can collect feathers, blood, oils and small tissue samples without killing the creatures. That's more than can be said for pollution itself. Dead birds are regularly found with bellies full of plastic, reflecting an increasing contamination from fishing refuse and consumer trash. The Monterey Bay Aquarium estimates about 1 million seabirds (plus some 100,000 marine mammals and sea turtles) die from ingesting plastics every year.
Plastic is a common sight on beaches, where tiny fragments can mix in with the sand. At Kimalo Point on Hawaii's Big Island, for example, microplastic fragments are found as deep as 3 feet (0.9 meters) under the sand surface. [Photos: Hawaii's Beaches Marred By Debris]
"[At] many places on the beach, it's hard to differentiate the sand from the plastics," Nicholas Mallos, an ocean debris specialist at the nonprofit Ocean Conservancy, told LiveScience in January after an expedition to the Big Island.
These plastics can be toxic themselves, leaching pollutants into the water, John Elliott said. And many ocean pollutants are hydrophobic, which means they don't mix well with water. These pollutants cling to plastics instead, meaning that when birds eat plastic pieces, they're getting a concentrated dosage of toxins.