Abstract: From October 2021 to April 2022, we conducted on-site investigations to study the overwintering and recovery process of algae in Houguan Lake, a typical eutrophic lake in Wuhan. The results of our research indicated the presence of six phyla and twenty-six genera of phytoplankton during the overwintering period in Houguan Lake. The dominant phyla observed were Chlorophyta, Bacillariophyta, and Cyanophyta. Regarding the temporal scale, the algae abundance in water started declining in early November (autumn), remained at a low level from December to next February (winter), and displayed an upward trend from March to April (spring). In contrast, the algae abundance in sediments exhibited an initial increase from October to November, followed by a decrease until the end of January and early February. Subsequently, it began to increase again, which is a delay compared to the algae abundance in water. Such delay could be attributed to the vertical migration of algae. Correlation analysis revealed a strong response of algal cell density in both the water and sediment to changes in water temperature (p<0.01). During the overwintering, a substantial number of cyanobacterial cells settled at the lake's bottom, which indicated that the algal cell density in both water and sediment were dependent on the changes of Chlorophyta and Cyanophyta, respectively. In winter (from November to next February), the ratio of algae abundance in water to that in sediment in Houguan Lake was relatively low, indicating that most algal cells settled in the sediment during this period. Our study unveils the overwintering and recovery process of algae in Houguan Lake, thus providing essential theoretical support for understanding algal bloom mechanisms and developing prevention and control strategies.

Key words: sediment provenance, algal overwintering and recovery, bloom prevention, phytoplankton, Houguan Lake