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Blooming bad: Study says Manitoba lakes most at-risk for pollutants

The two lakes in Manitoba included in the study, Killarney Lake and Lake Winnipeg, have among the highest rates of phosphorus recycling.

Algal booms at Killarney Lake in Manitoba.

Diane Orihel / Queen’s University

Algal booms at Killarney Lake in Manitoba.

Here's some news that might cloud your next trip to the lake.

A new national study has found that Prairie lakes, particularly those in Manitoba, are more vulnerable to the effects of pollutants than others across the country.

A study published Wednesday, co-authored by a University of Winnipeg researcher, dives into "phosphorus recycling"— a process that causes harmful algal blooms in ponds, lakes, reservoirs and wetlands across the country.

“In particular, what we found is that small Prairie lakes are particularly vulnerable to this process,” said Dr. Nora Casson, assistant professor in the geography department at UWinnipeg.

That means when pollution tarnishes lakes, it will continue to affect water quality for years – potentially decades – to come.

Farming debris and sewage are largely the culprits of toxic phosphorus inputs. The nutrient can then mix with sand or dirt at the bottom of the lake, moving in and out of the sediment to form algal blooms. The cycle continues to further pollute the lake.

The two Manitoba lakes included in the study, Killarney Lake and Lake Winnipeg, have among the highest rates of phosphorus recycling in Canada.

There are a number of reasons for that. For one, both lakes unfortunately boast a chemical cocktail rife for pollution. 

“And the pH of the water is kind of like the Goldilocks combination,” Casson said.

If the pH is too high, it cuts phosphorus levels. If too low, it has the same effect. But the pH levels in both lakes sits somewhere in the middle ground, producing the appropriate breeding ground for algal blooms to grow.

Both lakes are shallow, which means they’re easily mixed by the wind, making them all the more susceptible.

“It really points to the importance of mitigating pollution or stopping it from getting into the lakes in the first place. In our Prairie lakes, it’s going to take a very long time for them to recover,” Casson said.

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