Assessment of Stream Ecosystem Health in Huaihe Watershed Based On Benthic-Index of Biotic Integrity

Stream macroinvertebrate assemblages were sampled from 40 stations in Huaihe Watershed of China, among them 11 were unimpaired or lightly impaired stations and 22 impaired stations. Seventeen candidate metrics were calculated for establishing Benthic Integrated Biotic Index (B-IBI). Four metrics (total number of taxa, EPT taxa, intolerant taxa, biotic index) had the highest discriminatory power between impaired and unimpaired stations. Three scoring method, four scoring method, and ratio scoring method were used to get metrics into a uniform score and combined the B-IBI into an aggregated index. Discriminatory power analysis showed all of the three methods had highest discriminatory power (IQ=3). The correlations between three methods were all higher than 0.9. The accuracy comparison of assessment results based on the assessment criteria of ecosystem health using the three methods showed that the accuracies of three scoring method and four scoring method were better than ratio scoring method. The frequently used method, three scoring method, was employed to establish the B-IBI assessment criteria of ecosystem health of Huaihe Watershed. B-IBI criteria were: B-IBI>19.2, health; 19.2~14.4, sub-health; 14.4~9.6, good-fair; 9.6~4.8, fair; <4.8, poor. The assessment results showed that six stations were healthy, 5 stations sub-healthy, and the other 29 stations unhealthy.