Manitoba Prairie Lakes: In-lake remediation treatment summary

The report outlines various in-lake remediation strategies to combat eutrophication in Manitoba's prairie lakes, emphasizing that these treatments should complement efforts to control external nutrient sources. It details three biological methods (biomanipulation, floating treatment wetlands, and macrophyte removal), five physical/engineering methods (hypolimnetic withdrawal, dilution/flushing, hypolimnetic aeration, artificial circulation, and dredging), and three chemical methods (phosphorus inactivation, sediment oxidation, and algicides), providing their benefits, shortfalls, suitable lake conditions, and associated costs.

• The report argues that the primary focus of lake restoration must be controlling external nutrient sources, with in-lake remediation used to treat the "symptoms."
• Biomanipulation, which involves enhancing zooplankton grazing by removing planktivorous fish or adding piscivorous fish, is most successful in lakes smaller than 25 hectares and shallower than 3 metres, though results are often short-lived.
• Floating Treatment Wetlands (FTWs) use artificial platforms with macrophytes to sequester nutrients; for example, in Cargill Lake, FTWs would need to cover 29% of the surface area to reduce total phosphorus by 10% per year.
• Physical and engineering treatments vary in suitability: hypolimnetic withdrawal is restricted to deeper, stratified lakes, while dredging is generally limited to shallow lakes with depths of less than 3 metres.
• Chemical phosphorus inactivation using alum is a proven control but is restricted to a narrow pH range and can cause acidification in low-alkalinity lakes.
• Algicides, specifically copper sulfate, are considered ineffective for long-term treatment and are often legally restricted in most jurisdictions because they exceed Canadian limits for the protection of aquatic life.
• Artificial circulation can reduce phytoplankton biomass by increasing the depth of mixing and light limitations, but it results in the loss of deep coldwater fish habitat in stratified lakes.

APA

Lewtas, K., Roy, D., & Paterson, M. (2016). Manitoba Prairie Lakes: In-lake remediation treatment summary. International Institute for Sustainable Development. https://www.iisd.org/system/files/publications/manitoba-prairie-in-lake-remediation-treatment-summary.pdf

Chicago

Lewtas, Kimberly, Dimple Roy, and Michael Paterson. Manitoba Prairie Lakes: In-lake remediation treatment summary. International Institute for Sustainable Development, 2016. https://www.iisd.org/system/files/publications/manitoba-prairie-in-lake-remediation-treatment-summary.pdf.

Wikipedia

{{cite report |last1=Lewtas |first1=Kimberly |last2=Roy |first2=Dimple |last3=Paterson |first3=Michael |title=Manitoba Prairie Lakes: In-lake remediation treatment summary |publisher=International Institute for Sustainable Development |date=May 2016 |url=https://www.iisd.org/system/files/publications/manitoba-prairie-in-lake-remediation-treatment-summary.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{lewtas2016manitoba, author = {Lewtas, Kimberly and Roy, Dimple and Paterson, Michael}, title = {{Manitoba Prairie Lakes: In-lake remediation treatment summary}}, institution = {International Institute for Sustainable Development}, year = {2016}, month = may, url = {https://www.iisd.org/system/files/publications/manitoba-prairie-in-lake-remediation-treatment-summary.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }