In addition to their impact on environmental health, algal blooms are a concern for the households, businesses and governments that rely on freshwater bodies for drinking, recreation and aesthetic enjoyment. Algal blooms refer to mass growths of either “true” algae or of other microorganisms that resemble algae but are, in fact, bacteria. Excess phosphorus in water – primarily due to run-off – is a significant cause of algal blooms. Other factors include climate change, increasing water temperature and invasive species. 

Algal blooms are a concern for several reasons, including:

• potential harm to human and animal life (ex. blue-green algae); 
• increased decaying organic matter clogging water intakes, fouling drinking water, and harboring disease-causing bacteria (ex. Cladophora); and
• increased economic costs for management. 

Lake Erie is arguably one of the best-known Canadian lakes impacted by algal blooms; blooms are also occurring on a large and increasing number of freshwater bodies across Canada. This “rise of slime” has been most dramatic in the large, inland lakes found along the edge of the Canadian Shield: Lake Champlain, Lake Ontario, Lake Erie, Lake of the Woods and Lake Winnipeg. Many smaller lakes are also affected.

Despite the increasing extent and seriousness of the issue, an estimate of the total number of freshwater bodies affected by algal blooms across the country is not available today. No monitoring is done by the federal government and the approaches taken to monitoring by provincial agencies vary widely. Moreover, current monitoring approaches do not lend themselves to estimation of the total number of water bodies affected or to an understanding of the severity of the blooms in terms of area affected, duration or concentration of algae and/or toxins. No province provides anything today that could be taken as an accurate estimate of the total number of impacted water bodies within its boundaries. Given this, there is no possibility of estimating the total number of freshwater bodies impacted by HNABs (hazardous and nuisance algal blooms) in Canada based on data available today.

The full landscape scan on how the different provinces and territories monitor water bodies for HNABs can be found here.

Last updated December 2019