Mercury-contaminated fish populations can recover

An aerial view of the lake and surrounding forest where the study took place. (Photo by Paul Blanchfield)

According to the World Health Organization (WHO), being exposed to even small amounts of mercury may cause serious health problems, and can have toxic effects on humans. It’s also in their list of top ten chemicals or groups of chemicals that are a major public health concern. And one way humans are exposed to mercury is by eating fish that contain the organic compound.

But it now looks like there’s some good news for fish eaters.

Researchers who have been part of a 15-year study have just released results that show reducing mercury pollution entering lakes lowers how much harmful mercury is found in freshwater fish that are destined for consumers’ plates.

Dr. Britt Hall, a University of Regina biology professor, is part of the research team whose paper on the recovery of mercury-contaminated fish populations was published recently in Nature, the world’s leading research journal.

“During the study, scientists added a traceable form of mercury to a lake and surrounding forests and wetlands at the IISD Experimental Lakes Area in Ontario,” says Hall. “This is one of the only facilities in the world where lakes and their watersheds can be experimentally manipulated to determine the many ways in which humans are impacting lakes. And what we discovered there was that the new mercury we added quickly built up in fish populations, and then declined almost as quickly once additions stopped.”

Hall says this means that mercury concentrations in the fish populations recovered much quicker than previously understood, suggesting that curbing mercury pollution through policy initiatives will have rapid and tangible benefits regarding the quality of fish we consume.

Dr. Britt Hall, a University of Regina biology professor, is part of the research team whose paper on the recovery of mercury-contaminated fish populations was published today in Nature. (Photo by Kyle Leitch)
Dr. Britt Hall, a University of Regina biology professor, is part of the research team whose paper on the recovery of mercury-contaminated fish populations was published today in Nature. (Photo by Kyle Leitch)

“Technologies that can remove mercury from emissions are available and relatively straightforward. However, they do add expense to operations,” says Dr. Hall. “The Mercury Experiment to Assess Atmospheric Loading in Canada and the United States (or METAALICUS) showed that if society chooses to prevent Hg emissions, toxic mercury in fish will decline. It was a great honour and pleasure to be part of this experiment.”

The METAALICUS team applied about one teaspoon of a special form of mercury to a lake and its watershed. As new mercury inputs to the experimental lake were increased and then decreased in a controlled manner, the methylmercury in the lake water, surface sediments, invertebrates, and fish both increased and decreased quickly. Methylmercury is a much more toxic form of mercury that accumulates to high concentrations in many freshwater fish leading to many adverse, and even life-threatening, symptoms in humans. The decline occurred whether the mercury ‘rained’ directly onto the lake surface or entered the lake from the surrounding watershed in streams.

Researcher Lee Hrenchuk releasing a whitefish during the study. (Photo by Paul Blanchfield)
Researcher Lee Hrenchuk releasing a whitefish during the study. (Photo by Paul Blanchfield)

The findings provide indisputable, science-based support for necessary regulations on mercury emissions that have been undermined in recent years, especially in the USA. In addition, the findings support the efficacy of existing and new policies around the globe that seek to curb the amount of mercury that ends up in our environment.

For Hall, this experiment was particularly meaningful because it was also a family affair.

Her uncle, Dr. John Rudd, and her aunt, Dr. Carol Kelly, who are also mercury biogeochemists, were part of the team that initiated this research project. Fifteen years later, Hall is proud that their completed work has landed in such a highly regarded publication.

Dr. Kathleen McNutt, Vice-President (Research) says Hall’s contribution to this important paper demonstrates that University of Regina research make a difference in the world.

“Our scientists provide solutions to globally important issues in real-world settings,” says McNutt.

Nature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Read the full Experimental evidence for recovery of mercury-contaminated fish populations paper.