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Harmful algal blooms investigated in water bodies across Canada

Winnipeg – A new Canadian paper investigates the recycling of phosphorus, between sediment at the bottom of lakes and the overlying water.

This process contributes to the formation of the harmful algal blooms that plague many ponds, lakes, reservoirs, and wetlands across the country, the university said in a news release.

In Canada, tens or even hundreds of millions of dollars are invested every year in helping to manage nutrients – but in some lakes – legacy effects from nutrients recycled from sediments can linger and delay recovery from pollution, the release said. The primary impetus for this study was to understand where, when, and why this process occurs in Canadian freshwaters – knowledge that is critical for effectively managing algal blooms in polluted water bodies in this country and developing realistic goals for remediation.

Nora Casson, assistant professor in the geography department at the University of Winnipeg, and a co-author on the study, points out that the two lakes in Manitoba included in the study, Killarney Lake and Lake Winnipeg, are among the very highest rates of phosphorus recycling.

“This study has important implications for how we manage freshwaters in Manitoba,” Casson said, “Our lakes are among the most vulnerable in the country, and these findings suggest that by failing to control nutrient pollution today, we are contributing to water quality problems and algal blooms for years to come.”

By critically reviewing data from 70 water bodies, the authors found that phosphorus release from sediments was a common phenomenon in Canadian freshwaters, but that rates of this process varied dramatically among water bodies. The highest rates were found in small prairie lakes in Manitoba, Saskatchewan, and Alberta, while the lowest rates were found in boreal shield lakes. They also identified the main reasons for why this process differs among lakes, as well as the key priorities for future research.

The paper, “Internal phosphorus loading in Canadian freshwaters: a critical review and data analysis,” is written by Diane Orihel, Helen Baulch, Nora Casson, Rebecca North, Chris Parsons, Dalila Seckar, and Jason Venkiteswaran. It was published Sept. 13 in the Canadian Journal of Fisheries and Aquatic Sciences.