Trent University School of Environment professor Dr. Julian Aherne, and Environmental & Life Sciences Ph.D. student, Brittany Welsh ’16 are among 79 researchers belonging to the Global Lake Ecological Observatory Network (GLEON) who have co-authored a new report on plastic debris in global aquatic systems.

Professor Aherne, a former Canada Research Chair in Environmental Modelling, says this study gives us a better picture of the fate of plastic waste in the environment.

“Large scale collaborative projects are key to understanding solving global environmental problems,” says Prof. Aherne. “The primary focus for plastics and microplastics research has been marine environments. Through this international coordination, we were able to conduct the first globally comparable study on microplastics in freshwater by standardizing our sampling methods to compare data from water samples collected from lakes around the world.”

Microplastics prevalent in freshwater systems

The study looks at plastic debris in surface water samples collected across 38 lakes and reservoirs located in 23 countries, across six continents, with varying population densities and environmental conditions.

One of the main findings from the study, which is published in Nature, is that microplastic concentrations are equally, if not more, prevalent in freshwater systems compared to the marine (ocean) environment.

“The results show that freshwater systems are not just a transport pathway for plastics to the ocean. They are also a reservoir, meaning they can store and accumulate plastic,” says Brittany (Gzowski College), whose doctoral research on the fate of microplastics in background headwater lakes in Muskoka-Haliburton is supervised by Prof. Aherne.

Ranking highest in concentrations of plastic debris were Lake Maggiore in Italy, Lake Lugano in Switzerland, and Lake Tahoe in the U.S.

Among the first studies using standardized aquatic samples

This is one of the first studies to provide a global perspective on concentrations of plastic debris larger than 250 microns (93.8 per cent were classified as microplastic at five millimeters) in freshwater systems using standardized aquatic samples.

“These samples not only provide a consistent picture of plastic contamination in freshwater systems across the globe, but also allow for comparison between sites,” says Brittany.

Two local lakes studied

Working alongside Professor Aherne, Brittany collected surface trawl samples from two Muskoka lakes: Dickie Lake and Plastic Lake, ironically.

“Plastic Lake is an interesting catchment in that it’s a remote and pristine lake with no cottages or permanent dwellings. Yet, my work there shows that microplastics are being deposited in and around the lake,” says Brittany.

This contradicts an earlier-held notion that linked the presence of plastic in freshwater systems directly to anthropogenic (people-related) activities.

“We can use the data from this study to ask questions such as, ‘what drives the abundance in lakes,’ and bring greater awareness to microplastic contamination,” says Prof. Aherne.

As for how long microplastics stay in freshwater systems, the local sampling by Trent researchers found the residence period can be up to a decade.

Cleanup efforts need to focus on freshwater systems

Since freshwater systems are also used for drinking water and recreation, it’s important to focus cleanup efforts in this area.

“Identifying where the plastic is in the environment gives us important initial information on how to move forward with policy makers,” says Brittany. “We’ve already made some positive steps in the right direction by eliminating plastic straws, plastic bags, and plastic beads from our facial cleansers and cleaning products.”


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