Impacts of four emergent macrophytes on sediment nutrient loading

Acorus calamus, Zizania latifolia, Phragmites communis and Typha latifolia are four common emergent macrophytes in some wetlands. To evaluate the influence of the four emergent macrophytes on sediment nutrient loading, a field experiment was conducted. Sediment physicochemical characters, nutrient distribution properties and -N and -P fluxes were investigated. Compared with the control without macrophytes, sediment moisture content, porosity, loss on ignition and total P were higher, while wet bulk density, total N, -N and -N were lower. Concentrations of -N and -P in interstitial water were higher than in overlying water, indicating that they were diffusing from sediment to overlying water. -N and -P concentrations near the sediment surface displayed exponential increases with sediment depth and reached a maximum at 5–8 cm. Fluxes of -N and -P were also lower in sediment with macrophytes. Among the four macrophytes, sediment moisture content and porosity increased, while wet bulk density decreased with A. calamus and Z. latifolia. N and P contents were lower with T. latifolia, while -N and -N were lower with A. calamus and Z. latifolia. A. calamus and T. latifolia had lower -N concentration in interstitial water, and A. calamus had lower -P. Compared with other treatments, T. latifolia restricted -N and -P release effectively due to their lower fluxes (0.082 and 0.010 mg m−2 d−1). This study also elucidates the differences among the four macrophytes in affecting sediment nutrient loading, which is meaningful for macrophyte selection in wetland restoration.