Researchers hope Arctic char hold key to mercury mystery

Researchers from the University of Waterloo are trying to find out how mercury enters the Arctic food chain. (FILE PHOTO)

Scientists from the University of Waterloo hope tissue samples taken from char across the eastern Arctic will help determine how mercury, a harmful man-made contaminant, enters the Arctic food chain.

This summer students took tissue samples from fish as far south as Ungava Bay and as far north as Pond Inlet.

Graduate student Shannon Dorn looked at the levels of mercury in two types of char: those that live in lakes accessible to the sea and those, which are landlocked, trapped in lakes all year.

Landlocked char have higher mercury levels that fish that can run to the sea each spring, but she wants to know why, Dorn said.

To learn more about how this mercury enters the food chain, she tested not only char, but also the Arctic cod they prey on and plankton and invertebrates, other important parts of the food chain.

Dorn wants to know what impact climate change will have on mercury levels in char.

As temperatures increase the fish will be more active, so they are likely to eat more and accumulate more mercury.

But the opposite is also possible, that if the fish eat and grow more quickly, they may accumulate less mercury compared to their increasing size.

And older fish, not necessarily larger fish, usually have the highest mercury levels, she said.

Despite a lack of industrial activity, the Arctic receives mercury from atmospheric pollution from all over the world. Coal-fired power plants are considered to be the prime source of mercury pollution, with China, which relies heavily on coal, the worst offender.

Cold temperatures then pull this pollution from the high atmosphere down to ground level. There, predators pick up mercury from their prey and then pass this on when they’re eaten by animals higher up the food chain.

Arctic char, a staple food for Inuit, seals and polar bears, all contain mercury, which can be passed along to people.

Previous studies have found high levels of mercury in the breast milk of Inuit mothers.