York U study finds warming Arctic lakes can cause higher mercury accumulation

Cool Arctic lake, Cape Herschel (image: Katie Griffiths)
Cool Arctic lake, Cape Herschel (image: Katie Griffiths)

Mercury can show up in pristine high Arctic environments from as far away as China, and as the Arctic warms, more of that mercury can find its way into lakes, endangering people and wildlife, a York University geography professor has found.

“Mercury in certain forms is highly toxic to humans and wildlife. Since it is transported atmospherically over long distances, mercury produced in industrial centres in North America, Europe and Asia can end up in Arctic food webs, even without any local sources of mercury,” said lead researcher Jennifer Korosi, an assistant professor in the Faculty of Liberal Arts and Professional Studies at York University.

Cool Arctic lake, Cape Herschel (image: Katie Griffiths)
Cool Arctic lake, Cape Herschel (image: Katie Griffiths)

Korosi and her team used lake sediment cores to track the history of how mercury was, and continues to be, deposited in eight lakes on Cape Herschel (Ellesmere Island) in the Canadian high Arctic. Like the pages of a book, these cores allow researchers to track the history of mercury pollution over the past several hundred years.

“Our results indicate that, in some cases, climate warming does enhance the transport of mercury to lakes,” said Korosi. “But even lakes that have showed a delayed response to climate warming still exhibit a strong post-industrial signal of mercury enrichment, and no recovery following recent controls on mercury emissions.”

The concern is that the dramatic changes occurring in the Arctic in response to climate warming will cause higher amounts of mercury to be transported into aquatic ecosystems, where it can be converted into the toxic methylmercury form.

As Arctic ecosystems warm, there is more growth of plants, moss and algae in the lakes and the surrounding area that will bond with mercury, causing more of it to enter the aquatic system. This would delay the benefits of national and international policy agreements aimed at reducing mercury pollution in the environment.

The researchers looked at four distinct climate categories: lakes that responded early, around 1850, to a warming Arctic; those that were buffered from those early effects due to shade cover or other site-specific factors and didn’t respond to climate warming until about 1950; lakes that were always warmer than the norm for the Arctic; and lakes that have not yet been impacted by climate change, usually because they’re at a high elevation.

“By tracking mercury deposition histories in Arctic lakes that responded at different times to climate warming, we can determine whether the combination of climate warming impacts and long-range transport of industrial mercury emissions results in higher mercury concentrations in Arctic lakes than long-range mercury transport on its own,” said Korosi.

The study is published in the journal Environmental Pollution.

Video below: How climate change and mercury are interacting in the Arctic

Video below: A warming climate could mean more mercury is accumulating in Arctic lakes