Ecological responses of three emergent aquatic plants to eutrophic water in Shanghai, P. R. China

Eutrophication is the main pollution in urban water in Shanghai. In this study, three emergent aquatic plant species (Scirpus triqueter, Phragmites australis, and Zizania latifolia) were grown in monoculture, as well as a three-species mixture, to compare their effectiveness in terms of nutrient removal in controlled indoor constructed wetland microcosms. The effect of different aeration treatments (above-aerated, sediment-water middle-aerated, below-aerated, non-aerated) and treatments combining aeration and wetland plants for total nitrate (TN) and total phosphate (TP) removal efficiency was also examined. The objective of this study was to test the following four scientific hypotheses: (1) Plant growth will be optimal in the below-aerated treatment; (2) Z. latifolia will have the highest removal efficiency of TN and TP; (3) Aeration will increase the efficiency of TN and TP removal, with below-aerated treatment having the best effect; (4) The activity of microorganisms will vary over time, and aeration and plant treatment together will be most effective. We found that P. australis was most effective at removing TN and TP from water. Below-aerated significantly promoted the growth of P. australis. Hypotheses 1, 2 and 4 were supported by our results. The combination of P. australis and sediment aeration removed TN from water most efficiently. Above-aerated also effectively reduced TP in water. Combined plant and below-aerated treatments had better removal efficiency of TP from above-aerated than below-aerated alone. These results provide new insights into the management of eutrophication.