[Stream health assessment using a benthic-index of biotic integrity in Xitiaoxi Stream, Zhejiang Province, China].

ABSTRACT

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.