THE faeces of Arctic seabirds seem to be causing pollution hotspots in northern coastal ecosystems.
Wind and ocean currents have previously been blamed for high levels of toxic chemicals such as mercury, dioxins and polychlorinated biphenyls (PCBs) in Arctic air, soils, water, animals and people.
But, says Jules Blais from the University of Ottawa, Canada, these long-range transport models cannot explain why exposure is much higher in some communities than in others. 鈥淥ne thing the air and oceans can鈥檛 do is concentrate these chemicals into hotspots,鈥� he says.
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Blais鈥檚 team thought the real culprits might be Arctic seabirds, which can cover distances of 1000 kilometres on extended ocean feeding trips. So they headed to Cape Vera in the Canadian high Arctic, nesting ground of the northern fulmar, a type of petrel, to assess pollution levels.
The birds nest in dense cliff-side colonies of more than 20,000 individuals. Compared with soil and water far away from the bird colonies, ponds in the direct path of guano run-off had up to 10 times the amount of hexachlorobenzene, 25 times the amount of mercury and 60 times the amount of the pesticide DDT. The level of mercury exceeded the concentration Canadian authorities deem safe for wildlife (Science, vol 309, p 445). 鈥淪eabirds are very efficient concentrators of contaminants,鈥� says Blais.
鈥淚f we can show that these chemicals flow in predictable patterns, then we can alleviate the human problems just by altering food choices,鈥� he adds.
Anita Evenset, an ecotoxicologist working for environmental consultants Akvaplan-niva in Troms酶, Norway, has made similar observations in the Barents Sea. She argues that these hotspots must be taken into consideration when designing pollution monitoring programmes. Sampling from one site does not tell us about a whole region.
By identifying these hotspots, local people can be encouraged to fish in the least contaminated lakes, she adds. But whether birds or currents spread the pollution, 鈥渢he only real way to tackle the problem is at the source鈥�.
