[Choice of macroinvertebrate metrics for constructing a benthic-index of biotic integrity based on the disturbance gradients in the Qinjiang River Basin].

The selection of proper macroinvertebrate metrics was a key step in the successful construction of benthic-index of biotic integrity (B-IBI). In the context of lack of sufficient reference sites, the responses of biotic metrics to the stress gradients have been proved crucially important in metrics selection. We explored this using a data set (twenty-two sampling sites), where water environmental parameters, habitat quality index (HQI) and zoobenthos were measured and sampled using standardized methodology in the winter dry season (January, 2010) within the Qinjiang Rvier basin, Guangxi. Water quality stress gradients were synthesized using principle component analysis. Twelve out of the 38 candidate metrics were excluded because of high co-linearity ( [ r ] > 0.80, P < 0.05) with others. Multiple regression analysis of the rest twenty-six metrics, environmental gradients (PC I and PC II ) and habitat quality index showed that thirteen metrics significantly correlated (P < 0.05) with the environmental stressors (PCs and HQI). Eight of these metrics, family richness, Ephemeroptera richness, Coleoptera richness; Ephemeroptera, Plecoptera and Trichoptera (EPT) abundance, proportion of dominant species; proportion of predators; Shannon-Weaver diversity index for genus; and Biotic index (BI), satisfied the selection criteria (e. g., operational simplicity) and were thus candidates for developing a multimetric system to assess river health in our study region. We suggest that the response of metrics to environmental gradient is an ideal alternative for the construction of benthic-index of biotic integrity in the context of insufficient reference sites.