Activation of algicidal bacteria and nitrogen-phosphorus removal bacteria during controlling cyanobacteria bloom in Taihu lake by artemisinin algaecide.

Cyanobacterial harmful algal blooms (CyanoHABs) in Taihu Lake pose a persistent environmental challenge. This study investigated the inhibitory effects of artemisinin algaecide (AMA) on cyanobacteria in Taihu Lake and assessed its impact on nutrients, as well as the structures of particle-attached (PA) and free-living (FL) bacterial communities and potential ecological mechanisms. The results indicated that A-3 (0.8 g artemisinin/L) effectively inhibited CyanoHABs (inhibition rate = 93 %) and significantly increased the alpha diversity of PA and FL bacterial communities during the stationary phase， thereby promoting the proliferation of algicidal bacteria (AB) (e.g., Acinetobacter, Stenotrophomonas, and Exiguobacterium) and heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria (e.g., Acinetobacter, Stenotrophomonas, and Bacillus) through the utilization of dissolved organic carbon (DOC) from the dead cyanobacteria. This proliferation enhanced nitrogen metabolism and increased the abundance of nitrogen-cycling functional genes, improving nutrient cycling and enhancing system stability. The increased abundance of AB continuously suppressed cyanobacteria, while the proliferation of HN-AD bacteria removed nitrogen and phosphorus from the water, thus limiting nutrients available for cyanobacterial growth. Our findings demonstrate that AMA effectively inhibits CyanoHABs and prevents secondary blooms, providing a scientific foundation for the widespread application in cyanobacterial management, enhancing the effectiveness and sustainability of CyanoHAB control efforts.