Stream Health Assessment Using a Benthic-Index of Biotic Integrity in Xitiaoxi Stream, Zhejiang Province, China
底栖动物完整性指数评价西苕溪溪流健康

Stream macro-invertebrate assemblages were collected from 64 stream sites in Xitiaoxi Stream, Anji County, Zhejiang Province, China. Thirty-six candidate metrics were evaluated stepwise by distributing range analysis, discriminatory power analysis, and Pearson's correlation analysis. The B-IBI was composed of seven metrics: total taxa, EPT taxa, Coleoptera %, three dominant taxa, Hydropsychidae (Trichoptera) %, filterers %, and Biotic Index (BI). The ratio scoring method was used to transform the value of each metric into a uniform score. A variability coefficient method and an entropy method were used to calculate the weight value of each metric of the B-IBI. The measurement accuracy of the health criteria for the B-IBI derived from all sample data was better than that from only reference data. The entropy method had a higher accuracy (92.9%) than the sum total score method (85.7%) and the variability coefficient method (78.5%) in discriminating stressed and reference sites. The B-IBI health criteria for Xitiaoxi Stream were: B-IBI>0.69=healthy, 0.52-0.68=sub-healthy, 0.35-0.51=good-fair, 0.18-0.34=fair, B-IBI<0.17=poor. The Pearson's correlation analysis between B-IBI and chemical-physical variables showed that the B-IBI strongly corresponded with the habitat quality index (r=0.62, p<0.01), water temperature (r=-0.64, p<0.01), and altitude (r=0.64, p<0.01). Our results suggest that the B-IBI is a good indicator in stream health assessment and should be used in water resource management in China.