| Lake Erhai, the second largest lake in Yunnan Province in South-west China, is on the early stage of eutrophication which is sensitive and succession reversibly from vegetation-dominated water to phytoplankton dominated water. Ottelia acuminata was the typical clear-water submerged macrophyte and was the dominated primary producers in Lake Erhai before 1980, however, O. acuminata was almost disappeared due to water pollution and human destroy. After 2000, ecological restoration was carried out and good achievement was gotten in 58 Km-lakeshore. Pioneer plants were restored. However, it still suffered some ecological issues such as single dominant species, and unstable community structure after the repairation.Therefore, it is quite necessary to adjust the vegetation community structure and increase the biodiversity in lakeshore.In this paper,0. acuminata was researched,including research on restoration conditions and possibilities of O. acuminate by monitoring water and invesgating sediment in lakeshore and culturing O. acuminata in laboratory,and research on restoration technologies including seed germination,plant growth and planting were conducted.Also, restoration program was studied as well as restoration planting in lakeshore. The main contents and the results are as follows:(1) In summer and autumn, lakeshore water was worse than winter and spring and worst in November.The spatial variations were that pollution in north and western lakeshore respectively was much higher than southern and eastern lakeshore,and TN,TP and CODMn in lakeshore close to villages and farmlands were much higher than lakeshore near the forest and mountain lands.Under the strong wind-wave hydrodynamic force, TN,TP and CODMn in area close to lake bank(less than 60 m from lake bank,depth≤2.5 m) were significantly higher than area far away from lake bank(more than 60 m from lake bank, depth from 3.0 m to 8.0 m),however,under the weak wind-wave,there was no obvious differences between this two aeras.(2) Total nitrogen(TN),phosphorus(TP) and organic matter(OM) contents in surface sediment(10cm) were in the range 428-6864 mg/kg,600-1350 mg/kg,58-115 g/kg,and the averages were 1832 mg/kg,866 mg/kg,17.0 g/kg respectively.Sediment pollution with large regional changes in lakeshore was serious.TN and OM pollutions were distributed in large baies and areas closed to intensive villages,while TP pollutions were emerged in areas closed to intensive villages. There was significantly linear correlation between TN and OM contents in surface sediment in lakeshore as well each sedimentary column. In vertical changes,total nitrogen and organic matter contents in 0-30 cm depth of sedimentary column in different regions were mostly decreased with depth increasing,reflecting the impact of modern human activities had accelerated nitrogen and carbon deposition in the Erhai sediment.Phosphorus contents in each sedimentary column was disparate.(3) Water quality in Erhai Lakeshore could meet the requirement of restoration of O. acuminata, but spatial and temporal changes should be considered. Although surface sediment contamination in Erhai Lakeshore was more serious compared with other lakes in China and had big diffierences in different areas, some areas with less poluution were suitable for the restoration of O. acuminata.(4) The optimum germination temperature was 30℃and the most suitable photoperiod was Light/Dark=24h/0h and the most suitable substrate was clayed mud. The appropriate areas for O. acuminata restoration were lake bay in south of Pier Taoyuan, lake bay closed to Village Xingshengyi and Xiahe, lakeshore from Village Xiajiyi to Village Caicun, lakeshore from estuary of River Kanlong to Village Luojiuyi, lakeshore from the second pumping station in Dali City to the Olympic Center and lake bay in the east of Island Jinsuo.The best time for O. acuminata restoration planting was March to April and the best planting elevation was 1964.5-1962.5m (eighty-five elevation system).The most suitable substrate was hard substrates, sandy and clayey mud included.(5) The successful planting experiment in pilot site indicated that the restoration conditions exited in local areas of Lake Erhai.
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