| A benthic index of biotic integrity(B-IBI) was developed for application in estuaries health assessment of the Yangtze Estuary and its adjacent waters. Benthic macro-invertebrate samples were collected from 41 stream sites (13 non-degraded stations and 28 degraded stations) in the Yangtze Estuary and its adjacent waters in July, 2005. The analyses of the range of index value distribution, Pearson correlation and judgment ability were performed on fourteen candidate metrics. Six biological metrics were selected for the establishment of B-IBI, which were Shannon-Wiener index, the species number, total density, total biomass，Carapace Animals density percentage and Echinoderms density percentage. B-IBI was obtained by sum up all these indices after which were transformed into a uniform score by using the ratio scoring method. Base on 50 percentile of B-IBI value in reference sites, the criteria of health ranking was determined. The proposed criteria of benthic-index of biotic integrity were as follows: B-IBI >2.48 was regarded as health, 1.86-2.48 sub-health, 1.24-1.86 fair, 0.62-1.24 poor, and B-IBI<0.62 very poor. Assessing with these criteria, the results showed that among the 41 sites in Yangtze Estuary and its adjacent waters，7 sites were health, 2 sites were sub-health, 8 sites were fair，8 sites were poor and 16 sites were very poor. An independent data set sampled in June of 2006 was used to validate the index, the results indicated that final combined index correctly classified 89% of stations in the validation data set. |
