Abstract

The management and control of harmful cyanobacterial blooms remain a persistent global environmental challenge. This study evaluated the algicidal efficacy and ecological impacts of butanedione (BD), a naturally occurring agent, in aquatic microcosms that simulate real-world conditions. Special attention was given to the distinct roles of its two main photolytic products, peroxyacetyl radical (CH3C(O)OO•) and acetate (Ac). The results demonstrated that Ac exerted minimal short-term impact on cyanobacterial proliferation. In contrast, BD-derived radicals induced rapid cyanobacterial suppression, improving key water quality parameters in the early phase and subsequently supporting the recovery of eukaryotic algae. These radicals also markedly altered aquatic community structure, enriched beneficial photoheterotrophic bacteria, and suppressed functional pathways related to cell envelope biosynthesis. Notably, BD treatment reduced the abundance of antibiotic resistance genes (ARGs) and virulence factor genes, as well as the total relative abundance of potential bacterial hosts carrying both types of genes to 1/5 of that observed in the Ac-treated group. These results underscore BD’s dual functionality as an effective cyanocide with application potential, providing a scientifically grounded strategy for the sustainable management of harmful cyanobacteria-affected aquatic ecosystems.