Nutrient Sequestration by Two Aquatic Macrophytes on Artificial Floating Islands in a Constructed Wetland

Artificial floating islands (AFIs) have been documented as an efficient, environmentally friendly, and cost-effective solution to address nutrient pollution. However, most AFI studies to date have been conducted in controlled experiments, and AFI applications in natural settings, particularly in the U.S. Midwest, are limited. Here, we present the results of a combination of field and mesocosm experiments with two native aquatic plant species (Carex comosa and Eleocharis palustris) in a constructed wetland in north-central Ohio. Results showed that C. comosa outperformed E. palustris with respect to biomass accumulation and root system development. In natural conditions, C. comosa had a total dry biomass production of 58.5 ± 22.2 g/plug compared to 6.1 ± 3.2 g/plug in E. palustris. The maximum estimated mean nutrient storage for C. comosa was 20.24 g/m² of N and 1.33 g/m² of P, whereas it was 2.31 g/m² of N and 0.17 g/m² of P for E. palustris. In addition, the more developed root system of C. comosa suggests that AFIs containing this plant have better total nutrient removal capacity. The growth conditions of both species were significantly impacted by seasonal dynamics with respect to their biomass production and root elongation, as evidenced by reduced growth towards the end of the growing season.