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Wetlands may be solution to Lake Ontario’s beach water quality in Toronto

An evening view from the marshes of Humber Bay with the Toronto skyline in the distance

Lynda McCarthy is promoting the use of wetlands to reduce algae blooms along Lake Ontario shorelines, such as in Humber Bay Park (pictured above).

Co-founder of Ryerson Urban Water (RUW) Lynda McCarthy says that, responding to recent evidence of climate change locally, Toronto is in the process of planning mitigation efforts for extreme weather events alongside organizations such as RUW. One impact from massive rainstorms is the subsequent run-off that transports nutrients from the land into aquatic environments, which can create troublesome algae blooms along Lake Ontario shorelines.

With the help of wetlands, McCarthy is examining how to mitigate the impact of stormwater run-off by containing the nutrients from farmlands, which can flow quickly after major weather events like storms and impact larger bodies of water like Lake Ontario.

“After the storm of  [July] 2013, where we saw more rainfall in a one-day period than we did during Hurricane Hazel, it became clear that climate change was here and would result in more extreme weather events,” said McCarthy. “We learned that we will continue to see nutrients wash off from farmers’ fields into the lakes. We can either put up concrete walls to stop this run-off, or plant wetlands to decrease the impact to the water.”

In nature, much of the shore lands would be bordered by wetlands. However, urbanization of the Lake Ontario shoreline has all but eliminated the wetlands that acted like a filter for undesirable elements in the water. As a result, we see contaminated beaches in the summer, in particular after a major storm.

First attempts at improving shorelines through the introduction of plants to create wetlands were less than successful. The wetland grasses introduced became invasive and grew too quickly. Researchers now think that the key to reducing run-off impact may be an ancient crop grown for generations by the indigenous peoples of Canada, said McCarthy.

McCarthy and her team, including Master’s graduate student Francesca Fernandes and research colleague Vadim Bostan, have been in touch with an indigenous wild rice farmer from Peterborough to discuss how the grain could be used to create wetlands that would retain and filter the nutrient run-off along Lake Ontario shorelines.

“When we experience run-off, we see the algae growth explode and we get bad water quality very quickly,” she said. “If the project is successful, we could further examine the project to see if the crops yielded can be harvested for biofuel.”