A Preliminary Benthic Index of Biotic Integrity( B-IBI) for Bioassessment of the Plain Waterway Network of Taihu Basin

A preliminary Benthic Index of Biotic Integrity( B-IBI) was developed to assess the health status of aquatic ecosystem in the plain waterway network of Taihu Basin. Totally 21 candidate metrics were used to describe structure and function of macroinvertebrate assemblages from 13 reference sites and 62 impaired sites. The candidate metrics were evaluated by distributing range analysis, discriminatory power analysis and Pearson correlation analysis. The final B-IBI included total taxa number,molluscan taxa number, Shannon-Wiener index,percentage of three most-dominant taxa,biotic index and percentage of the filter-group. Finally,the scoring criteria of B-IBI were normalized based on the quadrisection system,and these scores were interpreted as excellent( ≥2. 84),good( 2. 13-2. 84),moderate( 1. 42-2. 13),poor( 0. 71-1. 42) and very poor( 0. 71). The results showed a relatively good heath for the southern-and-eastern lakeshores and the Daxi reservoir,and a poor health for the northern-and-western ones and its upstream river networks. The B-IBI can well differentiate the impaired sites from the reference ones,by giving a significant negative linear response to a gradient of chemical anthropogenic disturbances. In future,more works should be focused on strengthening standardization and localization of B-IBI for local government and managing agencies.