Assessment of water ecological health of transboundary rivers in Qiandongnan Prefecture based on B-IBI

Abstract

[Objective] In regions where multiple watersheds and multiple governance units intersect, the health status of river ecosystems is more complex. To identify the key factors of ecological degradation in transboundary rivers and to clarify the comprehensive influence mechanism of watershed environment and human disturbances, a health assessment of existing rivers is urgently needed. [Methods] A regional adaptive B-IBI evaluation system was established based on macroinvertebrate data from 66 transboundary rivers in Guizhou Province. From these, 26 representative rivers were selected. Two-way analysis of variance and redundancy analysis(RDA) were applied to determine the influencing factors of community structure in the transboundary rivers of Qiandongnan Prefecture. [Results] The result showed that the communities of large benthic macroinvertebrates were jointly driven by multiple environmental factors, exhibiting significant spatial differences and group dominance. A total of 108 benthic species belonging to 4 phyla, 7 classes, 21 orders, and 70 families were identified in the two major watersheds, with Arthropoda as the main dominant group. RDA revealed that COD_mn, dissolved oxygen(DO), total phosphorus(TP), and ammonia nitrogen(NH₃-N) were the main environmental factors driving differences in community structure across different governance unit combinations within the watersheds. Among them, the “Qiandongnan-Zunyi” combination exhibited the highest biodiversity, and the “Qiandongnan-Tongren” combination had the lowest. [Conclusion] The findings indicate that the structure and diversity of large benthic macroinvertebrate communities in the transboundary rivers of Qiandongnan Prefecture are jointly regulated by watershed differentiation and governance structure. It is recommended to introduce a “watershed-governance structure” coupling perspective to enhance governance adaptability, providing theoretical support and strategic suggestions for addressing ecological risks such as decreased ecological connectivity and habitat fragmentation.

Keywords

benthic organisms / multi-governance-unit rivers / biotic integrity / health assessment / watershed background / influencing factors / river ecological degradation / ecological risks