Assessing the ecological health of the Qingyi River Basin using multi-community indices of biotic integrity

Biological integrity refers to the capacity to sustain a healthy ecosystem comprising multiple biological communities within a region. Robust assessments of biological integrity thus require the sampling of multiple biological groups. We evaluated the ecological health of the Qingyi River Basin (QRB) using three indexes of biotic integrity (IBIs), including those based on the phytoplankton (P-IBI), zooplankton (Z-IBI), and benthos (B-IBI), and found that the health of the QRB system was “good” according to P-IBI (75.9 ± 17.9), Z-IBI (74.8 ± 21.8), and WQI (92.2 ± 5.3) and “moderate” according to B-IBI (43.8 ± 16.1). The assessments of the reliability of the three IBIs by exploring the relationships between biological communities and water quality environments from multiple perspectives revealed that the three IBIs were spatially positively correlated with WQI, Pearson and linear regression (P < 0.01). The results of redundancy analysis between the three IBIs, their constituent metris and physicochemical factors indicate that physicochemical factors have varying importance in determining the scores of the three IBIs. However, the scores of the three IBIs were lower than that of the WQI (P < 0.01), and B-IBI scores were lower than those of P-IBI and Z-IBI (both P < 0.001). In conclusion, IBIs are effective for evaluating the health of river ecosystems and could be widely applied. IBIs show greater sensitivity than WQI for detecting environmental damage, and B-IBI was the most sensitive index.