Interventions of river connectivity and land use on indices of biotic integrity (IBIs) in plain river networks

Biotic integrity in plain river networks is disturbed by various factors, such as land use and river connectivity, and combined effects are often neglected. In this research, the responses of zooplankton, periphyton (viz. algal), and benthic macroinvertebrate communities to environmental factors in the western Qingpu watershed were assessed at 33 river reaches utilising indices of biotic integrity (IBIs). The zooplanktonic index of biotic integrity (Z-IBI), periphyton index of biotic integrity (P-IBI), and benthic macroinvertebrate index of biotic integrity (B-IBI) were screened to explore the spatial variabilities in river conditions. The respective indices differed among the three communities, indicating that they react differently to stressors. Spearman's correlation and partial least squares regression analyses were employed to determine the influence pathways of river connectivity and land use on the Z-IBI, P-IBI, and B-IBI. The river connectivity parameters dominate the fitting of the IBIs, in which the morphological and hydrologic connectivity parameters are the critical factors and are significantly positively correlated with the B-IBI and P-IBI and negatively correlated with the Z-IBI. We offer insights into the impacts of river connectivity and land use on plain river networks and propose management strategies.