Biological Assessment of Pollution and Ecological Restoration of the Water Sources of the Dalianhu in Shanghai
上海大莲湖水源地污染的生物学评价与生态修复建议

The Dalianhu area is the key water source of Shanghai, covering an area of 14.6 km2. It consists of lake areas, aquaculture ponds, water-forest, river nets, swamps, and villages. In recent years, pollution within the region has become increasingly serious; its functions as to water sources have been gradually degrading, forming a new pollution source. In order to implement ecological restoration across the Dalianhu water sources, an investigation into the water sources area was carried out from July to August in 2008. Some measures on improvement of the ecological restoration were given on the basis of analysis of the pollution status and biological assessment of the pollution. Results show that there was generally phytoplankton of 86 species belonging to 48 genera of 7 phyla and zooplankton of 24 species belonging to 15 genera in the Dalianhu water sources during the study period. The dominant species of phytoplankton and zooplankton in the Dalianhu water sources were Phormidium sp., Merismopedia tenuissima, Cryptomonas erosa, Brachionus calyciflorus, Diaphanosoma brachyurum and Cyclops vicinus, which were all pollution-resistant. Pollution biological analysis shows that the Shannon Wiener index (H') of the phytoplankton in the Dalianhu water sources ranged from 1.60 to 1.99. The algal biomass range was (0.29 ~ 30.10)× 106cell / L, while the chlorophyll-a range was (7.63 ~ 246.91)ug / L, with the Carlson State Index (TSI) ranging from 51.8 to 84.6 and the Margalef diversity index from 1 to 10.4. All the indices indicate that the Dalianhu water sources were polluted to varying degrees, with the pollution level varying over space, where the water-forest, aquaculture ponds, and the inner river network showed relatively severe pollution. This had become the internal pollution source, followed by swamps, the lake area, and the external rivers, which were slightly polluted. Overall, the Dalianhu water sources could be taken to be moderately polluted. The restoration for the Dalianhu water sources can take into account layout reconstruction and communication between rivers and ecological restoration of lake functions. This study indicates that the Dalianhu water sources have lost a multitude of functions as to water purification and become a new pollution source. It is critical to conducting ecological restoration over the Dalianhu water source areas to maintain the safety of the drinking water in Shanghai.