Response of bacterial communities to benzalkonium chloride exposure in marine sediment systems

Benzalkonium chloride (BAC) is widely employed as a biocide due to its low toxicity, high efficacy, and broad-spectrum antibacterial properties, making it frequently detected across diverse environmental settings. However, the impacts of BAC on the marine microbial community remain poorly documented. In this study, the coastal sediment systems exposed to varying concentrations of BAC (0, 0.001, 0.1, and 10 mg/L) were constructed, and microbial responses were investigated. Results demonstrated that the activities of enzymes, including soil catalase, dehydrogenase, fluorescein diacetate hydrolyase, and neutral protease, increased on Day 1 following exposure to BAC. BAC increased the α-diversity of the microbial community on both Day 1 and Day 14 and played a deterministic role in community assembly. The microbial community structures were significantly shifted. Celeribacter , Fusibacter , and Flavobacterium increased especially on Day 1, while Gillisia , Sulfitobacter , and Marinobacter significantly decreased especially on Day 14. Functional prediction revealed that oxidative phosphorylation was promoted, suggesting that BAC might enhance the metabolic activity of the microbial communities. Network analysis showed that BAC reduced the complexity and potential correlations of the community, and genera from Pseudomonadota were highly connected within the community. Our findings revealed that BAC could substantially affect the microbial metabolism, composition, and interaction of marine sediment communities, thereby enhancing our understanding of the environmental impacts of BAC on marine ecosystems.