Eutrophication evaluation of the lakes under different water connectivity around Poyang Lake region

Lake eutrophication has become a major global water environment problem. In order to further explore the mechanism of hydrologic connectivity on lake eutrophication and effectively control lake eutrophication, this study selected Poyang Lake, Junshan Lake, Chi Lake, Taibo Lake and Yao Lake with different hydrological connectivity in Poyang Lake region as research objects. Comprehensive trophic level index (TLI) method was used to evaluate the eutrophication of lakes in different hydrological periods, and the influence of hydrological connectivity on eutrophication evaluation indexes and eutrophication state was analyzed on spatiotemporal scale. The results show that the change of hydrological period has little effect on the eutrophication of lakes, whether connected or obstructed. Except Yao Lake, which was in middle eutrophic state (60,70], the other four lakes were in light eutrophic state (50,60], which was consistent with the evaluation results of trophic status index (TSI). The eutrophication evaluation indexes of obstructed lakes were significantly different from those of rivers-connected lakes (p < 0.05), and the change of eutrophication evaluation index of obstructed lakes is more likely to be disturbed by human factors, while rivers-connected lakes are closely related to hydrological connectivity. At present, there is a risk of cyanobacteria bloom outbreak in Poyang Lake and its surrounding lakes. Therefore, this study suggests that strict control on point and non-point source pollution in the lake region and scientific and reasonable formulation of culture model will effectively prevent lake eutrophication and cyanobacteria bloom outbreak. This study is helpful to provide theoretical support for the study of the mechanism of lake eutrophication.