Lake ecosystem in Tai Lake (CH: Taihu) provide people with both direct and indirect benefits which are called ecosystem services. However, lake ecosystem services in Tai Lake have not well recognized and accurately quantified in past years. Decades of wastewater discharge, industrial pollution, and over application of chemical fertilizers around the basin have transformed this once meso鄄oligotrophic lake in the 1950s into its present hypertrophic state. As a result, cyanobacteria blooms appear during every summer in recent years, which may in turn have serious impacts on lake ecosystem functions and services delivery. In the late May of 2007, heavy cyanobacterial blooms dominated by Microcystis and their harmful metabolites occurred in the water columns of the northern region of Tai Lake resulting in a world鄄shaking drinking water crisis in Wuxi, Jiangshu Province, China. The best way to understand the deterioration of ecosystem service functions of a lake is to assess its ecosystem service values. Tai Lake, as a typical lake in eutrophication in China, was selected as a case study and data of ecosystems of Tai Lake were collected over the last 10 years. An integrated method of economy and ecology http: / / www.ecologica.cn was applied to estimate the value of lake ecosystem service functions. Ecosystem service functions of Tai Lake were divided into four main categories including provisioning, regulating, cultural and supporting services. The four categories were subdivided into eleven subcategories which covered water supply, aquatic products, shipping, climate regulation, soil and sand transportation, water purification, flood control, water resource storage, soil conservancy, maintaining biodiversity and tourism. Total values of ecosystem services for

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