Basin-scale aquatic ecosystem health assessment with composite indices of chemistry and aquatic biota: A case study of Dianchi Lake

Aquatic ecosystems play a crucial role in the process of human society development. Owing to the interference of human activities,health status of the most aquatic ecosystems was seriously threatened. On the basis of in-depth investigation of water quality and the ecological status of aquatic ecosystems in Dianchi Lake Basin,this study by using AHP method constructed a composite index system reflecting chemical integrity and aquatic biota integrity of the ecosystem. A composite health assessment indicator was calculated to assess comprehensively the aquatic ecosystem health status of Dianchi Lake Basin. The results showed that the health status of overall aquatic system was at a low level but varied among different parts of the watershed,i. e.the upper watersheds was good,the central part was moderate,while the lower part was moderate to very poor. The Dianchi Lake itself was at poor health condition,especially the north part( Caohai),while the health condition was better in rivers and reservoirs,but the differences between rivers and reservoirs was not significant. This study also indicated that the biological status was the major constraint contributing to the poor health status of the aquatic ecosystem of Dianchi Lake Basin.