Rapid rise of toxins in Mackenzie River fish caused by warming Arctic

By Martin Mittelstaedt

From Wednesday’s Globe and Mail Published on Tuesday, Feb. 09, 2010 10:11PM EST Last updated on Thursday, Feb. 11, 2010 3:11AM EST Scientists studying burbot in the Mackenzie River, one of the country’s most pristine rivers, have been surprised to discover that mercury, PCBs and DDT in the fish are rising rapidly, a finding they say is linked to climate change. The increase in the amount of harmful chemicals has been huge. In the period from the mid-1990s to 2008, PCBs have risen up to six times, DDT by three times, and mercury by 1.6 times in the burbot, a delicacy in the north described as tasting like a freshwater lobster. Contaminant levels “going up so dramatically was quite surprising,” said Gary Stern, a senior scientist with the Department of Fisheries and Oceans and lead researcher on the study, which also involved scientists from the University of Manitoba and Geological Survey of Canada. Dr. Stern said the most plausible explanation for the trend is that as temperatures in the Arctic rise due to climate change, snow and ice cover are diminishing, leading to a profusion of algae, zooplankton and other aquatic microscopic life able to absorb pollutants from water. While this greening of the Arctic environment means there is more for wildlife to eat, it also allows harmful contaminants to enter the food chain in far greater amounts, he said. The discovery of the rising tally of harmful pollutants in fish in such a remote area of the Northwest Territories was doubly unusual for researchers because contaminant levels should have been going down, based on the declining amount of the chemicals in the general environment. Both PCBs and DDT have been banned for at least the past quarter-century, while mercury concentrations have generally been stable or falling slightly. … “What climate change is doing is changing the [biological] availability of PCBs and the DDT that are already in the system,” Dr. Stern said. … A peer-reviewed paper outlining the findings appeared earlier this year in the journal Environmental Science and Technology. …

Mackenzie River’s fish contaminated with dangerous toxins: scientists