Salinity and Nutrient Uptake Potential of Two Plant Species in Constructed Floating Wetlands

Constructed floating wetlands (CFWs) are an emerging remediation technology that can remove myriad contaminants while providing uniquely valuable habitats. However, the nutrient removal efficacy of CFWs in brackish waters has not been well characterized, especially in coastal water bodies where salinity can fluctuate with tides and storms. To be effective in these settings, plants used in CFWs must be salt-tolerant and efficient at removing nutrients across a range of salinities. This study evaluated the effect of salinity (0.5, 5.0, and 18 g⋅L⁻¹) and nutrient concentration (low: 0.40 mg⋅L⁻¹ N and 0.06 mg⋅L⁻¹ P; high: 2.50 mg⋅L⁻¹ N and 0.38 mg⋅L⁻¹ P) on nutrient removal in CFWs using Spartina alterniflora and Juncus roemerianus over a period of ten weeks. Plant shoot height, biomass, and tissue nutrient concentrations were measured. Daily removal rates facilitated by J. roemerianus ranged from 15.2 (low) to 20.4 (high) mg^.m^−2.day⁻¹ N and 1.72 (high) to 2.40 (low) mg^.m^−2.day⁻¹ P. Daily removal rates facilitated by S. alterniflora ranged from 11.3 (low) to 15.8 (high) mg^.m^−2.day⁻¹ N and 0.80 (high) to 1.56 (low) mg^.m^−2.day⁻¹ PO₄-P. Both J. roemerianus and S. alterniflora are suitable species to remove N and P in CFWs under a wide range of brackish salinities. The results of this study will help coastal managers implement CFWs to improve water quality and build habitat in impoundments with fluctuating salinity.

Graphical Abstract