洱海流域湖泊生态系统健康综合评价与比较

基于2009年5月对洱海及其流域内的海西海、茨碧湖和西湖3个小型湖泊的水环境和浮游生物的调查,采用生态系统健康指数(EHI)和营养状态指数(TSI)法对其生态系统健康状态进行定量综合评价.结果表明:洱海流域湖泊整体处于富营养状态,健康状态较差;各湖泊健康状态存在空间差异:海西海和茨碧湖生态系统健康状态为中等,西湖和洱海健康状态为较差;而洱海湖泊内健康状态同样存在空间差异,北部和中部深水区较其他区域健康状态好.2种评价方法比较表明:洱海流域湖泊属于营养盐和生物量基本上呈正相关的响应型生态系统,生态系统健康指数(EHI)适用于洱海流域的生态系统健康评价.此外,整理分析洱海浮游生物历史数据,同样采用EHI法评价得出近20年来洱海生态系统健康状态呈逐渐恶化趋势,尤其1997年健康状态最差.

Comprehensive assessment and comparison of lakes' ecosystem health in Erhai watershed

The Ecosystem Health Index(EHI) and Trophic State Index(TSI) were used to assess the ecosystem health and eutrophic status of Erhai Lake and three small lakes(Haixihai,Cibihu and Xihu) in Erhai watershed.According to the field survey carried out in May 2009,all lakes in Erhai watershed were in an eutrophic status(averaged TSI =53.9) and in a worse ecosystems health status(averaged EHI =38.3).Further analysis found that the EHI has a high spatial variability among and between the lakes in Erhai watershed.Haixihai lake(EHI=42.7) and Cibihu lake(EHI = 42.1) had a median score of EHI;however,Xihu lake(EHI=33.5) and Erhai lake(EHI=37.9) had a lower score of EHI.Among Erhai lake,the north and central region had a higher score of EHI than the other regions.A comparison between EHI and TSI in assessing lake ecosystem’s status revealed that lakes in Erhai watershed belong to the response ecosystem that basically shows a positive correlation between nutrient and biomass,and the EHI is a good index in assessing ecosystem health of lakes in Erhai watershed.In addition,the EHI was used to assess the ecosystem health of Erhai lake in the past 20 years.The result indicated that ecosystem health of Erhai lake is degrading.The worst ecosystem state was observed in 1997,with a EHI value of 36.7.