The aquatic ecological health-state assessment and the influencing mechanism of Poyang Lake

Context. Freshwater lakes are still facing a series of problems, e.g. a decline in water quality, and a decrease in biodiversity. Thus, assessing the state of aquatic ecological health of the lake has drawn widespread attention from scholars both at home and abroad. Aims. This study aims to assess the state of aquatic ecological health of Poyang Lake and analyse the influencing factors. Methods. The long-term (2007-2018) site-monitoring data were analysed on the basis of the extension-evaluation method and correlation-analysis method. Key results. The results showed that the aquatic ecological health was mainly "good', and remarkable seasonal differences were observed. The seasonal order of relative aquatic ecological health could be expressed as the wet season being better than the dry season, whereas the rising season was similar to the retreating season. And the pollutant discharged into the lake was found to be the key factor, and the hydrological conditions led to seasonal differences in the state of aquatic ecological health of Poyang Lake. Conclusions. Consequently, scholars and policymakers should focus on both nutrient concentrations and hydrological conditions, which are the key factors influencing the aquatic ecological health of Poyang Lake. Implications. The results of this study have provided a theoretical and practical basis of the causes of ecological deterioration and should help with ecological-health protection of the large lakes connected with the Yangtze River.