For years, scientists have wondered how dangerous industrial and agricultural chemicals, long-banned in Canada, had concentrated in erratic patches across the desolate Arctic wilderness.
Were they deposited by wind or ocean currents? Were they dumped there on purpose?
According to a study released by the journal Science, the real culprit is the guano of the northern fulmar.
Also known as seabird poop.
The study found that the northern fulmar -- an Arctic bird similar to a seagull -- was responsible for the concentration of PCBs, mercury, DDT and hexachlorobenzene near nesting areas.
"The Arctic is not the pristine wilderness that people think it to be," said Jules Blais, associate professor of environmental toxicology at the University of Ottawa, and one of the leaders of the study.
Many people had thought chemicals that had been washed into the oceans could no longer affect ecosystems on land. So, the PCBs that most people assumed had vanished after the push to ban them in the 1970s seeped into the ocean and have now shown up in Arctic food chains.
"When these chemicals go out into the ocean, there's this perception that they will sediment out and that they'll be lost forever. Turns out, that's not the case," Mr. Blais said.
Research had found that the distribution of these chemicals, which can affect immune and endocrine systems and are probable carcinogens, was erratic across the Arctic. If wind or ocean currents distributed the chemicals, researchers would have found them more uniformly across the region.
Mr. Blais and his team of researchers, suspecting that the patchy distribution was caused by a biological link rather than a geographic one, measured the levels of chemicals in Cape Vera on Devon Island, south of Ellesmere Island. That cape was home to about 20,000 fulmars, concentrated in a small area.
Chemical concentrations under the nesting areas of these birds were up to 60 per cent higher than the surrounding landscape, Mr. Blais said.
"The seabirds are acting like funnels," he said.
The research team knew that these chemicals, used in everything from pesticides to mechanical insulation, would concentrate in food webs. The higher an animal is on the food chain, the more chemicals it will ingest from lower plants and animals.
Therefore the birds, which sit near the top of the food chain as they eat zooplankton, squid, fish and carrion, were not only receiving high doses of the chemicals, but passing them on to land through their excrement, which affects terrestrial ecosystems.
And "where you get seabirds, you get lichens and moss," Mr. Blais said. "We call them keystone species. They're single-handedly responsible for biological diversity in the area."
The birds introduce the industrial waste into land ecosystems largely unmarred by human habitation. And it's hurting more than just the northern fulmar.
"The top carnivores are getting the biggest dose of these chemicals," Mr. Blais said.
Whales and seals, which are major sources of food for northern aboriginal populations, suffer the same effects of chemical concentration. "Which is why aboriginal populations have some of the highest exposure to PCBs and mercury of any people on the planet," Mr. Blais said.
The Arctic is also more prone to chemical contamination because of something he calls the global distillation effect.
Many of the chemicals cited evaporate in warmer weather and are deposited in colder environments.
"There's a tendency for these chemicals to migrate to colder environments and the Arctic makes a natural repository," Mr. Blais said. "And once they get into the Arctic they start to affect the complex Arctic food chain."
The only solution is to ban the use of these chemicals globally. But, Mr. Blais said, as the dangers of PCBs and mercury become known, they are replaced by similar chemicals with equally disastrous effects. Flame-retardant chemicals such as perfluorinated acids and polybrominated diphenyl ether are emerging as new watchwords among the eco-savvy, he said.
"Some chemicals are dropping but they're just being replaced by other chemicals," Mr. Blais said.