The amount of mercury in Nova Scotia’s Kejimkujik National Park is puzzling researchers, nearly 20 years after scientists made the initial shocking discovery.

In 1995, scientists from Environment Canada discovered loons that were contaminated by the pollutant methyl mercury, leaving the birds with some of the highest levels in North America.

The scientists stumbled on the finding after blood samples were taken from loons and tested. The levels of methyl mercury were so high, one of the scientists later said he asked the lab to recheck the results.

Since that discovery, methyl mercury has been linked to reproduction problems at the park and at least one loon died of poisoning in the 1990s. There was some initial research, but no answers.

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Kejimkujik National Park was found to be contaminated by the pollutant methyl mercury, leaving the birds with some of the highest levels in North America. (CBC)

In recent years there's been renewed interest, including from some scientists at Acadia University.

Dr. Nelson O'Driscoll, the Canada Research Chair in Environmental Biogeochemistry, is looking at the root of the problem. He says the amount of mercury is increasing.

"Since those initial studies that were done in the early 2000s and late 1990s, there's also been work done by some of my students looking at dragonflies, rusty blackbirds," he says.

"Whenever you get near Keji, you start to see high amounts of mercury in the organisms. So, there's still a problem in Keji with high amounts of mercury and the question is — why is this area, what are the characteristics of this area that is causing this problem."

Sara Klapstein, a PhD student studying methyl mercury in lakes, is spending this week paddling the lakes of the park with a laptop and other instruments. She tests pH levels in the water, the penetration of solar radiation and takes water samples to be analyzed at Acadia's lab.

'It can get into plants, it can get into humans, as well as all the other wildlife that consume things from these lakes.'- Sara Klapstein

"Ultimately, methyl mercury is the form of mercury that is bio-accumulative," she explains. "So that means, it can get into plants, it can get into humans, as well as all the other wildlife that consume things from these lakes. If we can understand what's controlling that methyl mercury concentration within the water, that's kind of the root of mercury contamination higher up the trophic system."

The trophic system refers to the food chain, wherein small things are eaten by bigger things.

The primary source of mercury is burning fossil fuels, such as coal. It ends up in the atmosphere, swirls the globe for a couple of years and it comes back down to earth as rain.

The part puzzling scientists is the mercury that falls from the sky is not the same as the methyl mercury that ends up in fish and loons in the park. What is transforming the mercury is the big question.

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Mercury has been linked to reproduction problems at the park and at least one loon death in the 1990s. ((Parks Canada))

"It's particularly flat, so you tend to have a lot of wetlands," Dr. O'Driscoll says. "And when you have wetland, you have a lot of movement of decaying organic material called dissolved organic carbon moving into the lakes. It gives the water that really dark brown colour. And that colour of water, and that movement of carbon is really important. It's a key variable, in my opinion, in everything that happens in Keji."

One sample can cost up to $300

"Carbon is a food source for micro organisms, it absorbs solar radiation, it can bind things like heavy metals and contaminants and move things around that can instigate a lot of reactions that can change the form of mercury in the ecosystem."

There are other lakes in Eastern Canada with mercury problems, but studying the issue is costly. O'Driscoll says one sample can cost between $100 and $300 to analyze.