太湖五里湖生态重建示范工程——大型围隔试验

Ecological restoration engineering in Lake Wuli, Lake Taihu: a large enclosure experiment

五里湖是太湖北部富营养化程度最为严重的一湖湾．从2004年1月起,为了改善水质,重建五里湖生态环境,在五里湖南岸建立了一个面积为10×104m2示范工程试验区,采用多技术措施集成应用,开展湖泊生态重建技术研究．经过近2年的生态重建研究与实践,在示范工程试验区内建立了挺水植物、浮叶植物和沉水植物群丛23个,水生植物种类从生态重建前的零上升至15科、22属、32种,水生植物的多样性指数(Shannon-Wieher index)达到2．33,覆盖度达到40％- 55％．水质监测结果表明,示范工程区内水体的TN、TP、NH4-N、NO3-N、NO2-N及PO4-P的平均值分别比示范工程区外下降了20．7％、23．8％、35．2％、21．1％、45．6％和54．0％,TN、TP分别下降至2．50mg／L、0．080mg/L以下,水质得到明显改善,达到或低于“浅水湖泊稳态转换理论”指出的向“稳定清水态”转换的临界值,水体透明度(SD)平均值也有较大幅度提高,平均从0．39m提高至0．70m;初步实现湖泊水体从藻类占优势浊水态向大型水生植物占优势的清水态转变．因此重建与恢复湖泊生态系统要从沿岸带着手,首先重建湖滨带结构与功能,通过湖滨带水生生物一系列反馈机制, 逐步改善湖泊水质,最终实现沉水植被恢复;湖泊敞水区应主要采用生物操纵技术措施来实现湖泊生态恢复．

Lake Wuli is a hyper-eutrophic, shallow lake in China, situated near the Wuxi city in Jiangsu Province. It is a northern bay of Lake Taihu, which has a mean depth of 1.6 m, a maximum depth of 2.6 m and a surface area of 6.4 km^2. For improving water quality, from January 2004 a large-scale ecological restoration experiment（ 10 × 10^4 m） has been carried out in southwestern Lake Wuli. Main measures applied include setting-up a large enclosure for facilitating growth of submerged macrophytes, sediment dredging, fish removal, rehabilitating sediment, stocking piscivorous fish, planting aquatic macrophytes, stocking benthic animals and so on. The results showed that 23 aquatic macrophyte association had been set up, including 15 family, 22 genus and 32 species. The coverage of aquatic macrophytes increased from 0 to 40% -55%. Water quality has been markedly improved inside enclosure. The mean concentrations of TN, TP, NH4 - N, NO3 - N, NO2 - N and PO4 - P from August 2004 to July 2005 inside enclosure were 20.7% ,23.8% ,35.2% ,21.1% ,45.6% and 54.0% lower than those of outside enclosure. The mean concentrations of TN and TP were lower than 2.50 mg/L and 0.080 mg/L, respectively. Secchi depth was increased significantly from 0.39m to 0.70m. According to the results of this study, it is important and a first step to rehabilitate ecological structure and function in littoral of lakes, and to improve water quality gradually, and to establish submerged macrophytes at length. Biomanipulation could be applied to increasing secchi depth, reducing algal biomass and improving water quality in open area for whole lake restoration.