Nfld. & Labrador

Harmful mercury levels found in some N.L. coastal birds: study

A new study found some birds have mercury levels in what researchers term the 'sublethal' range.

"We've found mercury in almost every bird that we have sampled"

Samples of herring gulls from Newfoundland and Labrador showed fairly high levels of mercury in the study.

The mercury levels in a number of bird species in eastern and northern Canada, from herring gulls in Newfoundland and Labrador to northern gannets in Nova Scotia, are potentially harmful, a new study found.

"We've found mercury in almost every bird that we have sampled," said Mark Mallory, a biology professor at Acadia University and co-author of the study, published in April in the journal Ecotoxicology and Environmental Safety.

Mark Mallory said turrs, like the thick-billed murres seen here, are still safe for human consumption despite having mercury present in their bodies. (Submitted/Mark Mallory)

The researchers analyzed blood, brain and muscle tissue samples from 13 species from Nunavut, Nova Scotia and Newfoundland and Labrador, in an effort to provide a baseline snapshot of mercury levels in the birds. 

Some, like mallards, had only traces of mercury in their system, while others, such as the herring gull, measured in amounts the study's researchers termed "sublethal."

Mallory pointed to other studies which show sublethal levels of mercury in birds can result in impaired cognitive abilities and problems with eyesight. He said one species — dovekies, which overwinter in Newfoundland — has even been found to have laid smaller eggs.

"We're not seeing birds dropping out of the sky because of mercury poisoning," Mallory said, adding that although it is not his area of expertise, the levels found in the study don't represent a threat to human consumption at the moment.

"Turrs have elevated mercury, but not at levels that we would consider dangerous. And in general there's a lot of health benefits for eating country food," he said.

"If there were concerns, you would hear it from Health Canada."

A global problem

Mercury ends up in the birds' systems through a process called biomagnification, where the element is ingested by small organisms like phytoplankton, and then concentrates as it moves up the food chain to top predators, such as seabirds and tuna.

But where the mercury comes from in the first place is a global problem.

"The main source of mercury is emissions in the atmosphere," Mallory told CBC Radio's On The Go, saying those emissions come from numerous industrial sources all over the planet. Once in the atmosphere, that mercury falls indiscriminately over land and sea.

"You can find mercury at the North Pole, the Greenland ice caps, all the way down to Antarctica, that has been transported there from places where we've emitted it."

That in turn links with climate change and other human-created problems to create a complex web of stressors affecting the bird species Mallory studies.

You can find mercury at the North Pole, the Greenland ice caps, all the way down to Antarctica.- Mark Mallory

"The bigger picture is that mercury is just one of the stressors that these birds are experiencing," he said, adding, "it's difficult to tease apart the independent effects."

Not a 'lost cause'

Mallory labelled himself an optimist when it comes to reducing mercury levels in the environment.

"I definitely wouldn't call it a lost cause," he said, pointing to the Minimata Convention, an international treaty which holds signatories to promises such as banning new mercury mining. Canada ratified the convention in 2017.

"There is strong international recognition that mercury is a problem, a global problem, and it isn't just a wildlife problem," Mallory said.

Black guillemots, sampled from Nunavut, were another species with elevated mercury levels in the study. (Mark Mallory/Submitted)

He pointed to a study which has started to show signs of a plateauing in mercury levels in Arctic seabirds in recent years as compared to the 1990s. 

"Clearly, we have a lot of work to do. I don't want to minimize the issue ... but we can deal the problem, and we can fix a lot of this stuff."