Additives and biofilm formation on microplastics : insights from benzophenone-3 in polyethylene

Plastic additives are increasingly recognized as active agents that influence the behaviour and fate of microplastics in aquatic environments. This study investigates how the UV-filter benzophenone-3 (BP-3) affects biofilm formation and environmental aging of polyethylene microplastics (MPs) in freshwater. Comparisons between pristine MPs and BP-3-containing MPs (MP/BP-3) revealed that the additive altered polymer surface properties, crystallinity, and density even prior to environmental exposure. Presence of BP-3 destabilized the polymer matrix and promoted surface transformation during aging, while simultaneously suppressed biofilm growth, particularly of phototrophic microorganisms, and reduced extracellular polymeric substances and chlorophyll a content. Microbial community analyses showed a shift from cyanobacteria-dominated assemblages to heterotrophic, stress-tolerant taxa, accompanied by an enrichment of antibiotic resistance genes. Although microorganisms on MP and MP/BP-3 exhibited comparable genetic potentials for plastic degradation, the observed changes highlight a trade-off: BP-3 enhanced abiotic degradation while simultaneously inhibiting biotic degradation. Overall, BP-3 acts as an active agent that reshapes both the physical stability of microplastics and the structure and function of their associated microbial communities, with potential implications for aquatic ecosystem health.