The maintenance of aquatic ecosystem stability is fundamental to biodiversity conservation, yet the cross-trophic driving mechanisms remain elusive under intense anthropogenic environmental stress. Traditional “diversity-stability” theories often overlook the synergistic effects of multi-trophic interactions and the multidimensional facets of biodiversity (species vs. phylogenetic). This study investigates the Yongding River Basin, a typical anthropogenically disturbed system, by surveying macroinvertebrates, zooplankton, and phytoplankton across 109 sites. We constructed a comprehensive Aquatic Ecosystem Stability Index (AESI) integrating community constancy (1/AVD), interspecific competition (NPC), and network complexity (TC). The results demonstrated that ecosystem stability dimensions centered on community variation were more sensitive to biodiversity responses. Zooplankton species diversity ( Z -SD) was identified as a core positive driver of ecosystem stability, while macroinvertebrate diversity showed a weaker influence, likely attributable to habitat degradation. Intriguingly, a significant negative correlation was identified between phylogenetic diversity (PD) and stability across multiple trophic levels. This “atypical” relationship suggests that under high environmental stress, ecosystem stability is maintained through functional redundancy within closely related, stress-tolerant communities (low PD) rather than broad evolutionary lineages (high PD), due to the niche complementarity and functional compensation through stronger functional redundancy. Path analysis (SEM) indicated that chemical oxygen demand (COD Mn ) and total dissolved solids (TDS) indirectly suppressed system stability by altering the diversity levels of key trophic levels through the “habitat filtering” effect, while dissolved oxygen (DO) provides a critical ecological buffer by sustaining high-quality biological assemblages and cross-trophic interactions.“ Overall, the stability of the Yongding River Basin was driven by the “complementarity effect” across multiple trophic levels and the “functional redundancy” within communities. This suggests that in the early stages of ecological restoration of degraded rivers, priority should be given to constructing closely related functional groups with strong tolerance, shifting management focus from merely achieving “water quality compliance” toward “enhancing resilience based on biological integrity”. • Multidimensional stability decreased along an anthropogenic disturbance gradient. • Zooplankton richness is the core driver and early warning signal for stability. • Phylogenetic diversity negatively affects stability under environmental stress. • Functional redundancy via closely related species enhances ecosystem resilience. • A shift to trait-based restoration of “functional clusters” is proposed for rivers.
Zhang et al. (Fri,) studied this question.