Suitable plant combinations for ecological floating beds in eutrophic subtropical coastal wetlands under different salinities: experimental evidences

Abstract

The ecological restoration of coastal wetlands to remediate eutrophication has attracted attention worldwide. Although ecological floating beds have been widely used in freshwater ecosystems, selecting suitable plant combinations in coastal ecosystems where salinity changes dramatically remains a challenge. In this study, a controlled experiment was conducted to explore suitable plant species combinations with high purification efficiency and landscape aesthetics for ecological floating beds under different salinities. A total of seven plant combinations were planted in ecological floating beds in artificial eutrophic water with either freshwater or saline water (about 15 psu). After 6 weeks of growth, the concentration of nitrogen and phosphorus in water decreased significantly. Based on water purification efficiency, plant growth performance and landscape aesthetics, the combination with two freshwater plant species (Lythrum salicaria + Phragmites australis) and one mangrove species (Kandelia obovata) was identified as the optimal choice for low-salinity wetland habitats, whereas the combination with two mangrove species (Kandelia obovate + Bruguiera gymnorhiza) and one freshwater plant species (Canna indica) was the best for brackish wetland environments. With the proper designs, the ecological floating beds containing these plant combinations can be applied to the wetland restoration projects for both purification and beautification of coastal wetlands under the frequent influence of eutrophic and tidal water.