By Catherine Thompson
WATERLOO — Plastic is everywhere, and with good reason: it’s cheap, lightweight, and durable and can be turned into practically anything, from filmy plastic wrap to colourful children’s toys to vital components in a computer or a heart valve.
But scientists are discovering that plastic debris in the world’s oceans, and in large bodies of water such as the Great Lakes, could be a far more serious environmental problemthan previously realized.
Philippe Van Cappellen, an ecohydrologist at the University of Waterloo, holds up a couple of plastic Ziploc bags, carefully labelled with the names of beaches in Toronto and Burlington. They are filled with little bits of plastic — blue, red, yellow, white, green and clear, many of them smaller than confetti.
“Even on a beach that looks clean, if you start to look for them, you’ll find them,” he said of the small bits in the bags. Plastic “is often the forgotten contaminant of our aquatic environment.”
Because plastic is so durable, it doesn’t actually degrade in seas and lakes, but simply breaks down into smaller and smaller particles that can be easily gobbled up by birds, fish and other aquatic animals such as shellfish. Scientists are particularly concerned about “microplastics,” tiny fragments and fibres of plastic that are being found even within the muscle tissue of fish and other wildlife.
What’s more concerning is that plastic has been found to act like a sort of sponge, concentrating toxic chemicals that are diluted in oceans and lakes. Such toxins include heavy metals and chemicals that have long been banned, such as DDT or PCBs, that can have severe environmental effects and are known to cause cancer and birth defects.
“The durability of plastic makes it attractive, but it also makes it dangerous,” said Hans Dürr, a research assistant professor.
“These toxins get ingested in the food web,” and animals can spread the contaminants far and wide. Fish and shellfish that ingest microplastic could potentially transfer toxins up the food chain, where they could potentially end up on our dinner plates.
Research on plastics in the Great Lakes is quite new, and so scientists have many more questions than they have answers, said Van Cappellen: “How much of it is there? In what form? Where is it accumulating? How widespread is it? What are the consequences for organisms?”
There’s no historical data to show if the problem is getting worse over time, though the production of plastics has increased exponentially since the 1950s. And since plastic lasts for decades, if not centuries, it’s likely accumulating in the environment.
But some facts are becoming clear: “Now that people are starting to look at it, we’re starting to realize that (plastic debris) is very widespread,” Van Cappellen said.
Preliminary research has found plastic everywhere in the Great Lakes, with the highest densities in Lake Erie, the lake into which the other Great Lakes drain. Researchers have found everything from toys to food wrappers, the ubiquitous water bottles and cigarette butts (which are made from plastic fibre and are the most common form of plastic litter worldwide.)
“We’ve also been finding lots of plastic pellets,” said Alex Driedger, a master’s student working with Van Cappellen. The tiny, seed-sized pellets are the raw material of the plastic industry, which melts them and moulds them into useful products, from yogurt tubs to plastic combs. Microplastics like these move much more easily from one habitat to another, are most easily ingested by wildlife, and are the hardest to clean up, he added.
The researchers at UW are focused on two areas: perfecting ways to identify the types of plastic in the Great Lakes and where most of the plastic is.
Once we know what kind of plastics are out there, “you can start saying something about the sources of the pollution,” and you can start figuring out how to prevent or limit that pollution, Van Cappellen said.
His team is working on using spectrometry, which identifies the unique signal each material reflects from light. They’re artificially weathering different kinds of plastic, to see if the specific spectral signals of different plastics stay the same even after the plastic has been exposed to waves and sunlight.
They’re also working on using readily available satellite information to see if it can help identify where plastic is accumulating most in the Great Lakes.
Sharp changes in surface water temperatures and the amount of chlorophyll can indicate where currents converge in the Great Lakes, Van Cappellen said. “The working assumption is that where the currents converge is where the plastics are.”
Where the currents converge is often where aquatic life converges, he added, “so that’s where we should focus our attention.”
For many of us, plastic pollution has been seen more as a nuisance or an eyesore, Van Cappellen notes, rather than a pollutant with potentially serious health and environmental consequences.
He’s proud of the work his team is doing, and believes it is meaningful and important.
He fears, though, that the work will reveal a sobering message about how carefully we are caring for the Great Lakes.
“As an environmental scientist, to me, this is the tip of the iceberg.”
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