Abstract: We analyzed nutrient concentrations in different organs of Phragmites australis, Typha orientalis and Acorus calamus in various growth stages, dominant emergent plant species along littoral zone of Xukou Bay, Lake Taihu. Then, the removal of nitrogen and phosphorus was estimated based on nutrient concentration, biomass, as well as plant distribution. The results showed that total nitrogen concentrations in the sediments of littoral zone were 1373.0-2919.8 and 2240.6-3923.4 mg·kg^-1 in the flowering and fading stages, respectively, while total phosphorus concentrations were 437.1-687.3 and 556.0-790.7 mg·kg^-1, respectively. Total nitrogen and total phosphorus concentrations were significantly differed across organs of three emergent plants in both flowering and fading stages (P<0.05), with a trend of leaves > roots > stems. Total nitrogen and total phosphorus concentrations in the leaves and stems of three emergent plants in the flowering stage were higher than those in the fading stage, but an opposite trend of total nitrogen and total phosphorus concentrations in the roots. Total carbon concentrations in different organs were in the order of root ≈ stem > leaf, which did not significantly vary with growth stages. The highest total nitrogen concentration in leaves and stems was observed in P. australis and T. orientalis, respectively. Total nitrogen concentration in roots was similar among those three species. The highest total phosphorus and total carbon concentrations in different organs were observed in T. orientalis and P. australis, respectively. Harvesting the three dominant emergent plants in fading stage could remove 21.8 tons (18.47 g·m^-2) of total nitrogen and 1.6 tons (1.36 g·m^-2) of total phosphorus, and thus reduce the secondary pollution caused by in situ decomposition of aquatic plants.

Key words: cucumber, photosynthesis, ultrastructure., CO₂ enrichment, waternitrogen coupling