How U of T Trash Team tagged plastic bottles for the good of Toronto Harbour

In the summer of 2021, the U of T Trash team set out to discover where trash goes when it ends up in the harbour.

An image of a plastic bottle used in an experiment in Toronto harbour — Bottles like this were deployed from 13 different locations in the harbour and later recovered. (U of T Trash Team)

The following is a guest post from the U of T Trash Team, a science-based outreach group working to increase waste literacy and reduce plastic pollution. You can find a longer version on their blog.

Over the summer of 2021, while you were walking along the waterfront, taking a ferry to Centre Island, or swimming at Cherry Beach, you may have encountered bright orange water bottles drifting aimlessly through Toronto Harbour, but these water bottles weren’t litter — they were research.

We, the U of T Trash Team, launched the Tagging Trash project in collaboration with PortsToronto, Toronto Region Conservation Authority, Ontario Ministry of the Environment, Conservation and Parks, and University of Toronto Scarborough to learn how plastic litter travels in our harbour.

From April to August, we released orange GPS-tracked bottles from various points across the Toronto Waterfront, Harbour, and Islands. And after observing how our bottles travelled over a period of four months, we learned that litter gets into the nooks and crannies of our waterfront. Anywhere we found our GPS-tracked bottles, there were hundreds of pieces of litter.

Our bottles also revealed some really interesting movement patterns.

Read on for the breakdown, and check out the visualization accompanying this article to find one example of each pattern.

Trendy trackers

Most of our bottles travelled through Toronto Harbour for about one kilometre before becoming trapped or stranded on shore within a day of being deployed. These bottles, which have similar trends in travel, were typically recovered from sheltered areas like slips and bays, and under piers, docks, and boardwalks. This information lets us and policy makers know that most of the trash in the harbour likely comes from Toronto.

Litter that makes its way into the middle of the harbour tends to move with the prevailing winds toward the Keating Channel and the shipping channel. This is concerning because we suspect that plastics can be hit by boats and broken into smaller pieces of plastics, expediting the formation of microplastics. More trash-capture devices and local trash cans with lids will help prevent this.

Bottles also became trapped under city infrastructure or stranded onshore once they reached areas sheltered from the wind. Occasionally, large waves from storms would strand bottles on land and prevent them from travelling within the harbour.

Some bottles, however, were a little more adventurous.

Escape artists

While most of our bottles stayed in the harbour, the ones that didn’t left through the Western Gap more often than the Eastern Gap, and would soon beach.

To test if trash from Toronto’s popular beaches could travel farther into Lake Ontario, one of our bottles from deployment 3 — “John Tory” — was deployed from the southern end of Centre Island. During its journey, it spiralled its way to Ajax. The spiralling path demonstrates the Coriolis effect from Earth’s rotation.

An even more adventurous bottle, Onitariio, was released from the tip of Tommy Thompson Park to test if litter east of the harbour is likely to travel into the harbour. Remarkably, this bottle travelled across Lake Ontario for 300 km until its batteries ran out of charge near Rochester, N.Y.

An image of a plastic bottle used for an experiment floating underneath a dock at Bathurst Quay in Toronto — This bottle got stuck under the Pirates Life dock at Bathurst Quay. (U of T Trash Team)

Couch potatoes

Some bottles weren’t big on travelling and were retrieved only a few dozen metres from their deployment locations. They became stuck under the boardwalks near Harbour Square Park West.

While retrieving them, we found hundreds of pieces of litter from clothing, boating gear, food containers, and many microplastics. These hard-to-reach areas could use passive trash-capture devices (like Seabins) to make litter collection more feasible.

Surprises

We observed several of our bottles travelling up into the Keating Channel, and past the floating boom at the mouth of the Don River, which had been installed to prevent trash from flowing down the Don River and into Toronto Harbour.

This movement surprised us because we didn’t expect our bottles to travel against the water current, but we later discovered that the winds were strong enough to push our bottles upstream. This information suggests the need to improve the effectiveness of “leaky” booms.

Other bottles that surprised us were those that ended up in garbage cans, despite our outreach attempts. This made for some interesting fieldwork; we found ourselves digging through garbage cans like raccoons when searching for our bottles.

Although losing trackers to the garbage was frustrating at times, it showed that Torontonians care about the environment and feel a responsibility to keep their waters clean and plastic-free. We also saw, in real-time, the pathway our litter takes once thrown away — it heads to our city landfill located in London, Ont.!

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