New research by scientists at the University of Regina’s Institute of Environmental Change and Society shows that global warming is increasing levels of toxic algae detrimental to human health in prairie lakes.
Among the lakes affected are Pasqua and Crooked lakes — which border on Pasqua and Cowessess First Nations, respectively — as well as Buffalo Pound, which is the drinking water source for the City of Regina.
“What is particularly worrying is that the chance of exceeding toxin levels that cause acute human health effects has increased to one in four in several lakes in southern Saskatchewan,” said Peter Leavitt, a Canada Research Chair in Environmental Change and Society and co-author of the study.
Leavitt explained that urban growth and intensive agricultural activities increase pollution of freshwater with nutrients from fertilizers, which increases the growth of harmful algae known to produce potent water-borne toxins.
The study shows that nearly half of the surveyed prairie lakes had elevated levels of microcystin, a toxin from blue-green algae that appears as green scum in water. Late summer toxin levels were high in both the drinking water reservoir for Regina, Saskatchewan, and in downstream lakes bordering First Nations territories.
According to Leavitt, the high level of toxic algae concentrations makes the water less useful for drinking (when it is not treated) and will also be harmful for swimming and recreation.
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“Compounds which produce these waterborne toxins are more lethal than cyanide. If you were injected with it, it will be worse for you than when you are injected with cyanide,” the researcher said.
Leavitt added that there is evidence that these toxic algae are carcinogens that can cause cancer over a long period of exposure.
“Global warming will increase temperatures in southern Saskatchewan by three to five degrees. By studying the Qu’Appelle lakes for nearly 30 years, we have been able to show that a three-degree warming will nearly double the amount of toxin-producing cyanobacteria. The warmer it gets, the worse the problem will become,” Leavitt said.
The study’s authors, led by U of R research fellow Nicole Hayes, measured historical changes in climate, lake conditions, and toxins from blue-green algae over 11 years in six lakes of the Qu’Appelle River drainage basin. This area covers nearly 40 per cent of southern Saskatchewan, including most of Treat 4 territory, and drains directly into the Assiniboine River and Lake Winnipeg.
“While toxic algae are known to prefer warm waters, ours is the first study to demonstrate increased human health risk due to a longer growing season for algal blooms,” explained Hayes, now a faculty member at the University of Wisconsin Stout.
In addition to the Qu’Appelle long-term study, the scientists also conducted a mid-summer survey over 100 lakes in southern Saskatchewan. They found that 59 per cent of lakes exceeded drinking water guidelines for infants, while 42 per cent exceeded adult guidelines, and two lakes were near twice the levels known to cause acute human health effects.
Despite these findings, Leavitt notes there is some good news.
“Toxin levels in the Prairies were actually quite a bit lower than in the US Great Plains, where warmer summers promote more intense blooms of harmful cyanobacteria. As well, many Canadian water treatment plants have effective protocols for removing toxins from domestic water supplies.”
However, more of the problem lies with livestock, dogs and other animals who drink the water which can kill them, said Leavitt.
He said the research team have sent a copy of the paper to several of the First Nations including Pasqua and Cowessess because their territories are right close to the lake. The researchers recommend preventing the water in those areas from been fertilized in the first place because fewer nutrients in the water will mean fewer algae.
Rather than be complacent, society needs to address the underlying problems, said Leavitt.
He also added that the team have also sent a copy of the paper to the Saskatchewan Water Security Agency and hoping to get a government response.
Although the report focused mainly on lakes of southern Saskatchewan, the findings could be relevant to a region of nearly 15 million square kilometres; with similar findings expected for both Manitoba and Alberta.
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