Assessing the Native Plant Species for Phytoremediation of Freshwater Bodies in Southern Ontario, Canada

Many Canadian freshwater ecosystems are polluted by agricultural runoff, impairing their function with increased nutrient levels. Here, we simulated the water filtration function of wetlands, which uses aquatic plant species to create a phytoremediation system that can address the contamination of freshwater ecosystems with excess nutrients. We collected the water samples from three of Ontario’s freshwater bodies: the Holland Marsh, a highly agricultural area; the Nottawasaga River, a river in a rural area and part of a greater Nottawasaga watershed and Lake Ontario, near industrial sites in the Niagara region. To filter nitrogen (N), phosphorus (P) and potassium (K) from the collected samples, we determined the effectiveness of five local wetland and agricultural plant species: duckweed (Lemnoideae), watercress (Nasturtium officinale), coontail (Ceratophyllum demersum), thyme (Thymus praecox) and parsley (Petroselinum crispum). During a five-month experiment, plants were grown in collected water samples to determine their ability to uptake N, P and K. Along with monitoring their effectiveness in lowering nutrient levels, we tracked the health and growth of each plant species. The results showed that duckweed was the most tolerant to high nutrient concentrations and the most effective at overall nutrient reduction. From the Holland Marsh sample with the highest nutrient concentrations among all collected samples, the duckweed reduced N, P, and K by 11%, 53%, and 21%, respectively, compared to the control sample (i.e., with no plant). This filtration system allows for ecosystem restoration and prevention of further damage and contamination from agricultural runoff and nutrient pollution.