Mercury and the North’s lake bottom line

Thanks to natural, high-altitude transportation processes, mercury and other pollutants generated far to the south can enter northern food chains.

Thanks to natural, high-altitude transportation processes, mercury and other pollutants generated far to the south can enter northern food chains. These toxins evaporate into the upper atmosphere and drift north, far from the industries that released them. Eventually saturated, the atmosphere unloads the toxins into water bodies of Alaska, northern Canada and Siberia. There they accrue.

“Yes, it is unfair,” acknowledges researcher Nelson Zabel, a graduate student in biology at the University of Waterloo in Ontario. “Northerners have to deal with these influxes even though they are producing next to none of them,” says Zabel, who spent last spring and summer exploring mercury contamination and other fisheries-related issues at Kluane Lake.

First Nation governments and others concerned with northern watersheds and ecosystems are understandably troubled by the potential effects of that global distillation process, Zabel says. His thesis work, Mercury Dynamics and Paleolimnology of Kluane Lake, is part of a yet larger project initiated and supported by the Kluane First Nation.

Paleolimnology is the study of a lake’s history. By analyzing core sediment samples from present to over 1,000 years ago, and fish tissues of today, scientists hope to determine how severely these fish, and other creatures in Kluane Lake and its neighbouring environments, have been affected. They want to know how rapidly the atmospheric toxin-transportation process is working.

“We look at things like the amount of plant matter and algae that have been preserved in the sediment,” says Zabel. Different algae thrive under different lake conditions, whether colder or warmer, more acidic or more saline, for example. Scientists use the traces of various communities of algae over time to reconstruct the history of the lake. Mercury and photosynthesis have a strong relationship – understanding algae can help understand how mercury behaves in Kluane Lake.

They also analyze the sediments for metals, such as titanium, as well as mercury. The analysis allows researchers to determine how much mercury is part of the natural backdrop of the lake and how much has been added to the water from elsewhere and more recently.

Zabel first arrived in the Yukon late last March. “It’s a lot easier to take sediment cores from a frozen lake than it is from a moving boat, especially with the winds you get on Kluane,” he says.

“We collected our cores during the day and took them back to the Kluane Lake Research Station,” he recalls. “They opened a bit early in the year for us, so we were able to stay there and have their support while we were doing the coring – which was fantastic.”

The cores are columns of lake sediment collected in acrylic tubes. At the Kluane station the cores were divided into slices of one centimetre and one-half-cm thick. These were labeled by depth and core number and kept in a black plastic bag.

Zabel flew the cores home to his lab in mid April, making sure his samples remained cold and didn’t get lost in transit. He then had two months to undertake preliminary tests on the cores before he was scheduled to return to Kluane.

Among the tests was a series of high-temperature treatments called “loss on ignition” – LOI, for short. Tiny sediment samples, weighing about half of a gram, are heated in a muffle furnace, first at 90 degrees Celsius, then 550 degrees and then 1,000.

“LOI allows us to determine water content, organic content, carbonate content, and mineral content of the lake sediments,” says Zabel. “The sequential heating first evaporates the water, then burns off the organic matter, then burns off the carbonates.”

At the end of June, Zabel flew back to the Yukon, just days before the Kluane Lake Trout Derby was set to begin on Canada Day.

“We weren’t fishing in the derby but we partnered with the Kluane Lake Athletic Association of the Kluane First Nation to be part of their derby,” says Zabel.

He and his colleagues introduced themselves to derby anglers and explained that they were working with the Kluane First Nation on possible contaminants and nutritional values of the fish – lake trout, of course, as well as burbot and whitefish. “These three species employ different feeding strategies, and live typically in different parts of the lake,” he says.

The researchers asked anglers for the otoliths (a fish’s ear bones) and a small sample of fish flesh from each catch. “The sampling we did was pretty low impact,” says Zabel. “And we wouldn’t have been able to catch all those fish on our own. We ended up with about 115 samples in three days.”

In exchange for the samples, anglers would have their catch cleaned for free and offered a chance to enter a draw for a Go Pro camera.

Not all the research and results were a direct part of his master’s thesis work, says Zabel, but they were a component of the overall project KFN is doing.

Previous lake research undertaken in the Northwest Territories and Nunavut has revealed that variations in mercury concentrations are exceptionally high, says Zabel. “You can have lakes within a couple of kilometres from each other, where the fish in one may be unsafe and the fish in the other may be totally fine to eat.” That variation from water body to water body makes it difficult, at least for now, for scientists to draw all-encompassing conclusions about the North.

However, the potential for toxic effects is certainly there, scattered among water bodies, for those who rely on local fish for food. “We as humans, being large organisms, can accumulate a relatively high amount of mercury before it starts to affect us,” he says.

Mercury accumulates in protein-rich tissues, like muscle, says Zabel. Symptoms include loss of muscle control, memory impairment and loss of co-ordination.

On the other hand, fish is an incredibly healthy food source, rich in protective nutrients, such as selenium and omega-3 fatty acids. These can help protect the body against the harmful effects of mercury, and provide numerous other health benefits. Fish from Kluane Lake will also be analyzed for nutritional value, to help better understand the risks and benefits of these fish. “Like mercury, nutrients can vary greatly from species to species, and lake to lake. We’re trying to understand both the benefits and the possible negatives of fish in Kluane,” Zabel explains.

Zabel’s undergraduate degree is in physical geography. He is especially enthusiastic about how ecology and biology have interfaced with his original field to provide a study that is immediately essential from a human perspective. “It is so realistic; it’s a project I can really get behind,” he says.

So can a lot of other folks, including those at the Arctic Institute for Community-based Research, who are facilitating this research, and his faculty advisors, biologists Heidi Swanson and Roland Hall.

So what’s the next step in the project?

Zabel says, and laments, that 2015’s data collecting was so successful he won’t be called back to the beautiful wilds of Kluane anytime soon. “It’s lab work from here on in,” he says.

This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at