The Great Lakes are filling up with plastic

view of Lake Superior
CC BY 2.0 Mike Beauregard -- View of Lake Superior

Plastic is often thought of as an ocean contaminant, but it's in our freshwater lakes, too.

Thirty years ago, you wouldn't have wanted to eat fish from the Great Lakes, due to contamination by PCBs. These chemicals were allowed in North America up until the 1980s, at which point they were phased out, but their toxic and persistent effects were felt for a long time. Fortunately, efforts to clean up PCBs have brought levels down significantly, but now another environmental scourge is in the water.

Plastic, a contaminant that most people associate more readily with the world's oceans than its freshwater lakes, is a real problem for the Great Lakes. One report from 2016 provided the first-ever estimate of how much plastic enters the Great Lakes annually, and it's not pretty -- a shocking 9,887 metric tonnes.

The issue for the Great Lakes, as explained by professor Chelsea Rochman from the Department of Ecology and Evolutionary Biology at the University of Toronto (U of T), is that they're largely enclosed environments: "Unlike oceans, which get flushed out by global currents, the lakes are less diluted." As a result, the plastic concentrations are equal to or greater than those found in the oceans. Rochman's research in Lakes Ontario, Superior, and Erie has found microplastic particles in nearly all fish collected.

From a report issued by U of T Scarborough:

"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. [Rochman] 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."

Research into the Great Lakes' plastic problem is still in its infancy, but Rochman says it is well on its way to becoming a hot research topic: "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."

The fate of the lakes has major repercussions for the 43 million people who live in the Great Lakes basin. The region accounts for 58 percent of Canada's economy and, according to U of T professor George Arhonditsis, "$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."

Plastic is clearly a serious problem that affects far more people and animals than we realize at this point. While scientists continue to learn more about plastic's impact on wildlife feeding, reproduction, and survival, communities and municipal governments need to take strong action, in conjunction with the companies that manufacture goods made with plastic, demanding circular loop production and offering better reusable or biodegradable options.

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