Ottawa’s famed Rideau Canal has turned a bright shade of green, and experts believe a long hot summer in the nation’s capital is to blame.
The canal, which is classified as a world heritage site, is normally home to an abundance of aquatic plants that grow along the bottom and can be seen from the surface.
But another water-dweller has made itself at home this summer, explained Paul B. Hamilton, a botanist and researcher at the Canadian Museum of Nature who specializes in freshwater ecology.
“This year, with the extended sunlight that we’ve had, the warmer season and longer growing season, the algae – the green colour – are starting to out-compete some of the plants,” Hamilton explained.
“That’s why you’re going to get that green colour, and can’t see far down into the water.”
While the canal’s lock stations, which control the amount of water coming in and out of the system, are managed by Parks Canada, it’s Ontario’s provincial Ministry of the Environment and Climate Change that’s in charge of the water itself.
Gary Wheeler, a spokesperson for the department, confirmed that officials are looking into the odd colouring.
“Ministry staff conducted sampling Tuesday and we expect to have results back by the end of the week,” Wheeler said.
He noted that the canal is not a source of drinking water, but the ministry has notified the City of Ottawa Public Health Unit and Ministry of Natural Resources and Forestry.
This isn’t the first time the canal has taken on a hue perfectly suited to St. Patrick’s Day. The phenomenon “comes and goes,” said Hamilton, depending on the weather and conditions in the water.
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The last time it was this pronounced in the Rideau River system was in the 1960s and 70s, he said, but a bright-green canal will likely become more common in the coming decades as a result of climate change.
“We’re seeing (more algae growth) globally, in terms of the amount of growth and the extended growth into the fall … into October or November.”
Even now, with algae clouding it nearly to the bottom, the Rideau Canal water is unlikely to cause any serious health issues, Hamilton said.
“There is elevated bacterial levels in the downtown-Ottawa area in the canal, so you certainly would not want to be swimming in it. That’s just par for the course.”
If, however, the algae were to start producing micro-toxins, as happened in the 1960s, Hamilton said that could become a more serious problem.
These micro-toxins, if they appeared, would not be fatal to humans, but could cause skin irritation and serious gastrointestinal issues. If dogs or cats were to come into contact with them, they could prove fatal to the family pet.
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According to Hamilton, not much can be done for the canal in the short term. Over the next decade, officials may want to look at trying to control the amount of nutrients that get into the water, which would help to limit the algae blooms.
The ducks that float along the canal in the warmer months are also a good indicator of the water quality, he added.
“They could be our ‘canary in the river’ scenario. If the water’s an issue, you won’t see the ducks there.”
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