Seabird droppings are leaving more than a foul mess in the Arctic -- they are contaminating northern lakes and ponds with extremely high levels of mercury and DDT, said a study carried out by Canadian researchers.

Concentrations of the chemicals were found to be as much as 60 times higher in bodies of water on Devon Island in Canada's Nunavut region, than in other Arctic areas, said the study to be published in the journal Science.

Inland layers of sediment less than a cm thick were analyzed last summer at Cape Vera, 1,800 km north of Iqaluit on the island's north shore, where 20,000 northern fulmars nest annually.

The samples revealed that their guano, laden with mercury, DDT,PCBs and pesticides, gradually oozed down fortress-like cliffs 250 meters high and into surrounding shallow freshwater lakes and ponds.

The fulmars, which look like the common seagull and dine on zooplankton, squid and fish in the Atlantic Ocean, are picking up the pollutants from their aquatic feast and funneling the waste back into relatively untouched ecosystems, said John Smol, a biology professor at Queen's University in Kingston, Ontario.

In doing so the birds are creating a "boomerang effect" where by industrial pollutants thought to be forever lost in the ocean hundreds of km away are returning to the continent and threatening land species.

"(Water) insects are eaten by the birds, the birds are eaten by the foxes," Smol said. "It's quite possible we have a whole new mechanism of (pollutants) going back in to the terrestrial ecosystem."

The birds are the dominant species in the region and are single-handedly responsible for biological activity in the area, said Jules Blais, an environmental toxicology professor at the University of Ottawa.

That makes their impact on the local environment more pronounced, said Blais, who suspects the phenomenon is not limited to Devon Island, the largest uninhabited island in the world.

There are other seabird colonies distributed throughout the Arctic that would have this kind of effect because they nest in large densities together, said Blais, who led the study.

There are about 10 million seabirds that colonize the Canadian Arctic, creating a risk that humans could be exposed to dangerously elevated levels of the pollutants.

Northern Canadian populations are already among the most mercury- and PCB-exposed people on the planet, and their diets, largely derived from Arctic freshwater systems, put them at greater risk, researchers said.

The study highlights the need for industries to be more environmentally sound in their practices, Blais said.

Source: Xinhua