Floating Treatment Wetlands and Plant Bioremediation: Nutrient treatment in eutrophic freshwater lakes

The report evaluates floating treatment wetlands (FTWs) as a nature-based solution for eutrophication in shallow lakes. Through primary research at the IISD-Experimental Lakes Area (IISD-ELA) and a case study of Pelican Lake, Manitoba, the study demonstrates that FTWs—particularly those using cattails—effectively sequester phosphorus and nitrogen. While plant biomass contributes to nutrient removal, the report emphasizes that the microbial biofilm on roots provides up to 80% of the total treatment. For Pelican Lake, the study estimates that 5% surface coverage could reduce total phosphorus levels by 10% to 50%, though FTWs must be combined with watershed-level strategies to meet provincial water quality standards.

• Floating treatment wetlands (FTWs) serve as a viable 'natural infrastructure' alternative to conventional in-lake remediation for smaller eutrophic water bodies, offering additional benefits such as shoreline protection from wave erosion and wildlife habitat enhancement.
• Research at the IISD-ELA showed that cattails are opportunistic nutrient consumers; a relatively small increase in phosphorus loading led to rapid increases in plant productivity, biomass production, and phosphorus uptake.
• The majority of nutrient removal in FTW systems is performed by the microbial biofilm coating the roots and island surface, rather than the plants themselves, with biofilm accounting for up to 80% of the treatment.
• In cattails, the roots are the primary site of phosphorus sequestration, containing significantly higher concentrations of phosphorus than aboveground shoots.
• For Pelican Lake, Manitoba, it is estimated that covering 5% of the lake's surface with FTWs could reduce total phosphorus (TP) levels by 10% to 50%, depending on the system's removal efficiency.
• FTWs alone are insufficient to bring Pelican Lake's total phosphorus concentrations below the Manitoba provincial guideline of 0.025 mg/L, as the lake's 2016 mean TP was 0.305 mg/L.
• To maximize nutrient removal, the report suggests harvesting aboveground plant biomass in August or September to prevent the reintroduction of nutrients into the water column during senescence and winter freeze-thaw cycles.
• The most effective remediation strategy for eutrophic lakes involves combining in-lake treatments like FTWs with watershed-level nutrient reduction strategies that target both internal and external loading sources.

APA

Grosshans, R., Lewtas, K., Gunn, G., & Stanley, M. (2019). Floating Treatment Wetlands and Plant Bioremediation: Nutrient treatment in eutrophic freshwater lakes. International Institute for Sustainable Development. https://www.iisd.org/system/files/publications/floating-treatment-wetlands.pdf

Chicago

Grosshans, Richard, Kimberly Lewtas, Geoffrey Gunn, and Madeline Stanley. Floating Treatment Wetlands and Plant Bioremediation: Nutrient treatment in eutrophic freshwater lakes. International Institute for Sustainable Development, 2019. https://www.iisd.org/system/files/publications/floating-treatment-wetlands.pdf.

Wikipedia

{{cite report |last1=Grosshans |first1=Richard |last2=Lewtas |first2=Kimberly |last3=Gunn |first3=Geoffrey |last4=Stanley |first4=Madeline |title=Floating Treatment Wetlands and Plant Bioremediation: Nutrient treatment in eutrophic freshwater lakes |publisher=International Institute for Sustainable Development |date=October 2019 |url=https://www.iisd.org/system/files/publications/floating-treatment-wetlands.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{grosshans2019floating, author = {Grosshans, Richard and Lewtas, Kimberly and Gunn, Geoffrey and Stanley, Madeline}, title = {{Floating Treatment Wetlands and Plant Bioremediation: Nutrient treatment in eutrophic freshwater lakes}}, institution = {International Institute for Sustainable Development}, year = {2019}, month = oct, url = {https://www.iisd.org/system/files/publications/floating-treatment-wetlands.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }