Influence Of Different Ecological Restoration Measures On The Nutrients In The Sediments Of The West Wulihu, Taihu Lake

West Wulihu Lake locates in the north of Taihu Lake, it is beside the Meiliang Lake, and in the southwest of Wuxi City. It is one of the hypereutrophic areas in Taihu Lake, and the water quality was worse than V level standard in 2001. Since 2003, the project of "Environmental dredging and ecological restoration of heavy polluted water body", which belonged to the national key research project ("863"project), was carried out to improve the water quality, including returning the fishing pond to lake, dredging and ecosystem reconstruction demonstration project (aquatic vegetation restoration) in different areas. In this research, water quality parameters, phosphorous and nitrogen in water, and sediment cores of different areas were investigated in different seasons. It aimed to examine the significance of different restoration measures on biogeochemistry of phosphorus and nitrogen. In addition, by the growth of biofilm, the accumulation phosphorus and nitrogen in the biofilm of different lake areas were investigated. It was helpful to understand the growth rule and effect factors of biofilm, as well as comprehend the biogeochemistry of phosphorus and nitrogen in the water ecosystem.The results showed that, the distribution of nitrogen and phosphorus in the water and sediment under different ecological restoration measures were different. The content of nitrogen and phosphorus in the water in only-dredging area and control area was higher than other lake areas. Macrophytes reestablishment after dredging affected Lab-P,Al-P,Fe-P mostly, followed by Ca-P and Org-P. In the former-fish poud area, Ca-P and org-P accounted for the largest proportion in the total phosphorus, followed by Fe-P. However, Fe-P and Ca-P accounted for the largest proportion in the dredging only area. Compared with TP, the effects of ecological restoration measures on TN were not so obvious. In dredging only area, the contents of nitrogen and phosphorus in both the water and sediments were high, the long-term effects of dredging needed to monitor in further study. In the area of dredging plus macrophytes reestablishment, the contents of TN and TP were the lowest. It was suggested that the effective way to lake eutrophic control may be actualizing through reestablishment of aquatic macrophytes in the dredging area after the precondition of reducing external source pollution.The study of biofilm showed that, biomass, volume and thickness of the biofilm increased with the growth period in natural aquatic system. The phosphorus content of biofilm increased with the growth period too, while nitrogen content did not. The growth rate, biomass, phosphorus and nitrogen content of the biofilm at the water depth of 30cm was higher than that 100cm, indicating that light was a important effect factor to the growth of biofilm. Better diaphaneity and DO, lower velocity of flow, with abundant aquatic biology were also found to be propitious to form complex biofilm, and to the enrichment of phosphorus and nitrogen in the biofilm.