Plastic pollution isn’t just a problem in our oceans. It’s also affecting the Great Lakes

Plastic bottle in the ocean
An upcoming international science conference held at U of T Scarborough will explore pressing issues affecting the Great Lakes, including pollution from plastics. (iStock photo)

Don Campbell

When it comes to plastics polluting our water, it’s not just the world’s oceans we need to worry about says U of T assistant professor Chelsea Rochman.

“The contamination in the Great Lakes and other bodies of freshwater from plastics and microplastics is ubiquitous,” says Rochman, whose lab focuses on the fate of plastic debris and its associated chemical contaminants.

She points to published research, in addition to work in her lab and with colleagues, that finds the concentrations of plastics in areas of the Great Lakes are equal to or greater than those reported in the ocean. Their work in Lake Ontario, Lake Superior and Lake Huron has also found microplastics (particles five millimetres and smaller) in nearly all fish collected.

This shouldn’t come as much of a surprise, says Rochman. Canada and the United States discard about 22 million pounds of plastic into the Great Lakes annually and unlike oceans, which get flushed out by global currents, the lakes are less diluted.

Most plastics end up in the Great Lakes from storm water runoff through rivers or streams, from wastewater treatment plants, or litter blown directly into the lakes. She says some other sources include agricultural runoff and maritime debris like fishing gear. Rochman’s own research on microplastics has uncovered pollution from tiny bits of tire dust, microfibers from clothing, glitter, plastic bottles and microbeads found in face wash. 

“Toxicity tests in the lab show that microplastics can be harmful to wildlife, impacting growth, feeding behaviour, survival and reproduction,” she says.

Rochman says a lot of the research on plastic pollution in the Great Lakes is still in its infancy, but it’s becoming a hot topic of environmental research. One line of her lab’s current research focuses on how plastics move through Great Lakes food webs, and how this contamination may affect local aquatic wildlife.   

Chelsea Rochman
Assistant Professor Chelsea Rochman (right) is an expert on water pollution from plastic contaminants.  

“It’s exciting to be part of a group of researchers that are really moving the needle on microplastics in freshwater. I think the research we will see in the next few years will be eye-opening.” 

Pollution from plastics is just one of many environmental issues that come into focus during the annual conference of the International Association for Great Lakes Research (IAGLR), taking place June 18 to 22 at U of T Scarborough.

It’s the largest scientific event held in the Great Lakes area with more than 800 participants from countries all over the world, and will feature more than 50 scientific presentations.  

“The Great Lakes comprise a tremendously valuable resource … and that’s an understatement,” says Professor George Arhonditsis, chair of the Department of Physical & Environmental Sciences at U of T Scarborough and co-chair of the conference.

The Great Lakes basin is home to 43 million inhabitants in Canada and the U.S. It accounts for 58 per cent of Canada’s economy, while $311 billion of Ontario’s annual annual exports derive directly from its natural resources, including municipal and industrial water supplies, fish harvesting and land uses, he notes. 

“There’s no question it’s an invaluable economic resource, but it’s also home to numerous natural aquatic habitats that, in many ways, remain under threat,” says Arhonditsis, who is an expert in food web ecology and biogeochemical modelling.

In addition to pollution from plastics, there’s the constant threat from parasites, invasive species, algae blooms, habitat loss and various other forms of pollution. Compounding the ecological threats is the challenge in developing effective environmental policy to protect them. The Great Lakes form a water border between Canada and the U.S., while its jurisdictions also include one Canadian province and eight U.S. states.

“We will have leading experts covering important environmental issues facing the Great Lakes, the important scientific research being done in the lakes as well as sessions on governance and environmental policy,” adds Arhonditsis.

Mathew Wells
Associate Professor Mathew Wells does much of his research in the Great Lakes. 

While issues certainly remain, Arhonditsis and fellow conference co-chair Mathew Wells, an associate professor in the Department of Physical & Environmental Science, both note that a lot of important work has been done over the past few decades in cleaning up the Great Lakes.

“Just 20 to 30 years ago you couldn’t safely eat the fish in the Great Lakes because toxic PCB levels were so high,” says Wells, an expert on environmental fluid dynamics

“Much of that has changed because the water quality has improved and the reason comes down to good science and environmental agreements made between Canada and the United States. Problems exist, there's no doubt, but in many respects there are great news stories about the work that’s been done.”