2. Materials and methods2.1. Descri

2. Materials and methods
2.1. Description of three small lakes
Three small shallow lakes, named Dadang Lake (DD), Chenwan
Lake (CW), and Xitang Lake (XT), are located in the south Taihu Lake
region, China (Fig. 1). The outflows of lakes were through Hengshangang
River (HSG) and Xiaomeigang River (XMG), finally into Taihu
Lake. The area of each lake was less than 40 _ 104 m2, and its depth
no more than 2 m(Table 1). Several villages and lots of farmlands are
around the lakes, the sewage inflows are composing by domestic
sewage and farm drainage. Water temperature varied greatly in a
year, being the highest in summer (July or August with an average
temperature of 30.3 _C) and the lowest in winter (January with an
average temperature of 6.1 _C; Qin et al., 2002) in this study.