Permafrost study could help forecast mercury levels in Dehcho Lakes

Scientists are back in the Dehcho region of the Northwest Territories this summer, trying to find out why some lakes have higher levels of mercury than others, and if thawing permafrost is contributing to the problem.

"From a scientific perspective it's part of a huge puzzle that we are trying to put together," says Heidi Swanson, associate professor with the University of Waterloo, "of what is going to happen across the circumpolar Arctic with climate change and mercury."

Swanson is part of the research team that's working with the Jean Marie River First Nation on the multi-year project, which is being funded by the territorial government, the Aboriginal Aquatic Resources and Oceans Management Program, the Northern Contaminants Program, and Health Canada.

More than a decade ago people in Jean Marie River started noticing "relatively high levels" of mercury in fish from several lakes in the region, including Sanguez Lake, Ekali Lake, McGill Lake, Deep Lake and Gargan Lake. Those levels led to consumption advisories — still in effect — suggesting limits on the types, size and amounts of fish that are safe to eat.

Most of the mercury in fish in the North actually comes from the South.

"Whenever there is a coal-fired plant or fossil fuel burning, mercury gets released into the air and it makes its way north and falls into lakes," says Swanson. "There's (also) a lot of mercury and carbon that are locked up in frozen ground.

When that frozen ground thaws, scientists aren't sure how that will affect mercury levels in lakes, Swanson says.

"Unfortunately what we know is that it's complicated."

Predicting future effects

The researchers hope answering that question will help them predict future impacts of thawing permafrost — and climate change.

This summer's research will focus around McGill Lake and the impact of thawing permafrost and its potential mercury release on country food. The team will take core samples of permafrost, look at different levels of mercury at different depths, and make comparisons to learn more about hydrology and water flow.

"Sometimes there's a pretty thick layer of organic material and sometimes it's a thin layer and clay and gravel underneath," says Swanson. "We do know the thicker the layer of the peat and twigs... the more mercury is stored there. We want to know how the water flow differs."

This season's fieldwork involves both Cyrielle Laurent of Geo Cardinal Services Corp., and Louis Philippe Roy of the Yukon Research Centre. 

'Health advisory scares people'

The health advisories issued so far take pains to point out that eating fish from the affected lakes is safe in moderate amounts — mercury becomes dangerous as it accumulates. But that hasn't alleviated all fears.

"The health advisory scares people" says Jean Marie resident Angus Sanguez, who does environmental monitoring for the Dehcho First Nation. He worries the advisories will continue as the ground warms.

"There's a lot of permafrost thawing… there's a lot of big changes.

"You see a lot of landslides into the Mackenzie River….and a lot of drunk trees — mainly poplar — uprooted and falling over the place."

According to Swanson, the community of Jean Marie River has played a big role in climate change research.

"It was really them who came up with the research questions and have facilitated everything with fishers and boats and people to work with " says Swanson, who does research in all three northern territories.

"This particular project... serves as an example of what great science can happen when scientists listen to communities and really take into account their priorities."