The reinvasion and recruitment of overwintering cyanobacteria in sediments in spring have an important impact on cyanobacterial blooms in summer and autumn, but until now, this process has not been observed in natural water bodies. In this study, wireless sensors and automatic water sample collection systems were used to carry out continuous high-frequency monitoring of cyanobacteria and related environmental indicators in Meiliang Bay, Lake Taihu, during a northwest wind event in spring. The results showed that there were many dormant cyanobacteria seeds in the sediments of Lake Taihu. These cyanobacterial seeds were easily resuspended from sediments, allowing them to reinvade and remain in the overlying water. Simultaneously, the water temperature exceeded the recovery temperature after the northwest wind event and the available light was sufficient to allow the reinvading cyanobacteria to recruit. The circadian photosynthetic rhythm of these recruited cyanobacteria eventually led to a rapid increase in dissolved oxygen in the water body during the south wind phase to a supersaturated state, and periodic diurnal fluctuations of the water body dissolved oxygen saturation curve. This study provided direct evidence for fully understanding the annual cycle of cyanobacterial blooms.
Keywords: Cyanobacteria; Field observation; Recruitment; Reinvasion; Sediment resuspension.