An experiment with 27 simulated wetlands in northern China demonstrated that constructed wetlands planted with macrophytes (large aquatic plants) remove more nutrients than unplanted wetland systems. Nutrient uptake by plants accounted for 14-52% of Total Nitrogen removal and 11%-34% of Total Phosphorus removal.
Wu, Haiming, Jian Zhang, Peizhi Li, Jinyong Zhang, Huijun Xie, and Bo Zhang. (2011). Nutrient removal in constructed microcosm wetlands for treating polluted river water in northern China. Ecological Engineering, 37(4), 560-568.