Abstract: Clarifying water quality tendency and its responses to extreme weather in Xukou Bay of Lake Taihu is critical to water management. Here, 他 the water quality tendency of Xukou Bay from 2016 to 2022 was reported, and its responses to water temperature (WT) and water level (WL) were tested as well. The results show that the water quality of Xukou Bay was relatively stable. Moreover, the total nitrogen (TN), ammonia nitrogen (NH₃-N), total phosphorus (TP), and COD_Mn concentrations decreased gradually. However, the annual average WT increased rapidly, with an average rate of 0.086 ℃·a^-1, presumably threatening the ecological stability in this basin. Redundancy analysis (RDA) confirmed that although WT and WL contributed to less than 5% of total variation of the water quality, the effects caused by WT were significant (P＜0.01). In contrast, WL was failed to explain the changes of water quality. Nevertheless, TN, NH₃-N, COD_Mn, and pH were sensitive to high WT (＞30 ℃), and high WL (＞3.8 m) significantly and affected the concentrations of NH₃-N, TN, TP, and chlorophyll-a. In summary, the ecological environment of Xukou Bay was stable, but high WT and high WL are the main factors interfered the stability. This study provides significant references for water quality management under extreme weather conditions.

Key words: Lake Taihu, Xukou Bay, extreme weather, high water temperature, high water level