Manitoba Prairie Lakes: Eutrophication and In-Lake Remediation Treatments

The report evaluates a wide array of in-lake remediation techniques to combat eutrophication, emphasizing that these methods are generally only effective if external nutrient loads are simultaneously reduced. It categorizes treatments into biological engineering (e.g., biomanipulation, floating wetlands), physical engineering (e.g., hypolimnetic withdrawal, dredging, artificial circulation), and chemical applications (e.g., alum, Phoslock, algicides). The document provides detailed case studies from North America and Europe, analyzing the effectiveness, longevity, and costs of each method, while highlighting the critical role of internal phosphorus loading in delaying lake recovery.

• Eutrophication is driven by excessive loading of nutrients, organic matter, and silt, and while often anthropogenic, it is also a "natural aging process for lakes and reservoirs".
• In-lake remediation technologies are typically not effective unless external nutrient loads are also reduced and controlled.
• Internal phosphorus loading from sediments often delays lake recovery after external loads are reduced, with release typically occurring for more than 1015 years, and in some cases over 20 years.
• Biomanipulation, which involves removing planktivorous fish to increase zooplankton grazing on algae, is most successful in shallow lakes (depth < 3 m), though long-lasting results are rare.
• Floating Treatment Wetlands (FTWs) remove nutrients through microbial transformation, macrophyte assimilation, and volatilization, and are most efficient in small lakes, ponds, and retention ponds.
• Hypolimnetic withdrawal removes phosphorus-laden bottom waters to shorten retention time and decrease anaerobic conditions; it is restricted to deep, stratified lakes with high internal loading.
• Artificial circulation can reduce algal biomass by increasing mixing depth and light limitation, but may cause the loss of deep coldwater fish habitat and increase overall lake temperatures.
• Dredging of surficial sediments can provide a reliable and permanent solution to internal loading if the top 0.30.5 m of a sediment core is removed, provided external loads are reduced by at least 50%.
• Aluminum sulfate (alum) is a proven control for phosphorus inactivation, but it is restricted to a narrow pH range and can be toxic to fish and macroinvertebrates in acidified conditions.
• Phoslock (lanthanum-modified bentonite clay) is effective over a wider pH range than alum and does not affect pH levels, but there are concerns regarding the potential toxicity of lanthanum.
• Sediment oxidation (Riplox) uses nitrate injection to prevent the development of ferrous iron and subsequent phosphorus release, but it is only effective where iron redox reactions control P fluxes.
• Algicides like copper sulfate provide only temporary relief and are now rarely used due to toxicity to non-target biota and the risk of releasing cellular toxins like microcystin.

APA

Lewtas, K., Paterson, M., Venema, H. D., & Roy, D. (2015). Manitoba Prairie Lakes: Eutrophication and In-Lake Remediation Treatments. International Institute for Sustainable Development. https://www.iisd.org/system/files/publications/manitoba-prairie-lakes-remediation-literature-review.pdf

Chicago

Lewtas, Kimberly, Michael Paterson, Henry David Venema, and Dimple Roy. Manitoba Prairie Lakes: Eutrophication and In-Lake Remediation Treatments. International Institute for Sustainable Development, 2015. https://www.iisd.org/system/files/publications/manitoba-prairie-lakes-remediation-literature-review.pdf.

Wikipedia

{{cite report |last1=Lewtas |first1=Kimberly |last2=Paterson |first2=Michael |last3=Venema |first3=Henry David |last4=Roy |first4=Dimple |title=Manitoba Prairie Lakes: Eutrophication and In-Lake Remediation Treatments |publisher=International Institute for Sustainable Development |date=December 2015 |url=https://www.iisd.org/system/files/publications/manitoba-prairie-lakes-remediation-literature-review.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{lewtas2015manitoba, author = {Lewtas, Kimberly and Paterson, Michael and Venema, Henry David and Roy, Dimple}, title = {{Manitoba Prairie Lakes: Eutrophication and In-Lake Remediation Treatments}}, institution = {International Institute for Sustainable Development}, year = {2015}, month = dec, url = {https://www.iisd.org/system/files/publications/manitoba-prairie-lakes-remediation-literature-review.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }