With the improvement of public requirements for the health status of aquatic ecosystems, there have been innovative assessment methods developed for aquatic ecosystems. In this study, benthic algae assemblages and water quality variables were analyzed to develop a benthic diatom-based index of biotic integrity (D-IBI) for the assessment of the aquatic environment in the Lalin River. In addition, using redundancy analysis (RDA) based on dominant species and physicochemical indexes, the ecological distribution characteristics of the benthic diatom community were revealed, and the key influencing factors were identified. The results showed that the benthic diatom community structure in the Lalin River basin had obvious spatial differences. The application of the index revealed that the water quality could be described as excellent condition in the upper reaches of the Lalin River, good to common condition in the middle of the sites, and moderate to poor condition in the downstream. The assessment further revealed that the main reason for the degradation of the Lalin River ecosystem was nutrient enrichment through agricultural land use.
Keywords: Lalin River; benthic diatom; biological integrity; community structure; health assessment.