Development and Validation of a Benthic Diatom Index of Biotic Integrity (BD-IBI) for Ecosystem Health Assessment in the Songhua River Basin

The Songhua River, as the third-largest river in China, has garnered increasing attention for its ecological health. This study established a water ecological health assessment system for the Songhua River Basin based on the BD-IBI. Through a comprehensive analysis, including distribution range analysis, discriminant ability analysis, and correlation analysis, 97 candidate indicators were evaluated. Among these, IDSE Leclercq (IDSE), Indice Diatomique Artois Picardie (IDAP), RA. motile individuals, RA. ß-mesosaprobic, and RA. polysaprobe were selected as the core indicators for BD-IBI construction in the Songhua River Basin. The water ecological health status of the Songhua River Basin was categorized into five levels. Furthermore, environmental factors influencing BD-IBI and water quality were analyzed using box plot analysis, redundancy analysis (RDA), and multiple linear regression model. The results indicated that while the Songhua River Basin exhibits an overall “Good” water ecological health, marked heterogeneity exists across sub-reaches. Specifically, the Tangwang River exhibited the highest BD-IBI score, while the Woken River showed the lowest score. Key water quality factors driving BD-IBI changes include DO, EC, NN, TN, TP and QHEI. These findings provide a valuable reference for the assessment and restoration of water ecological environment quality in the Songhua River Basin, promoting the sustainable development of aquatic ecosystems.