Exaggerated interaction of biofilm-developed microplastics and contaminants in aquatic environments

Biofilm-developed microplastics (MPs) may serve as important vectors for contaminants in aquatic environments. Elucidating the interactions between biofilm-developed MPs and coexisting contaminants is crucial for understanding the vector capacities of MPs. However, little is known about how the adverse effects of contaminants on MP surface-colonized biofilms influence their vector capacity. In this study, we aimed to investigate the interaction mechanism of biofilms colonizing the surface of MPs with coexisting contaminants using microcosm experiments and biofilm characterization techniques. The results indicated that the biofilm biomass on polystyrene increased over time, providing an additional abundance of oxygen-containing functional groups and promoting Cd accumulation by biofilm-developed polystyrene. Moreover, as a coexisting contaminant, Cd exerted adverse effects such as additional mortality of microorganisms and senescence and MP-colonized biofilm shedding. Consequently, the contaminant vector capacity of biofilm-developed MPs could be mitigated. Thus, the adverse effects of coexisting contaminants on biofilms influenced the ability of MPs to act as vectors in aquatic environments. Neglecting the negative effects of contaminants on biofilms may lead to an overestimation of the contaminant vector capacity of biofilm-developed MPs. This study provides support for more accurate assessment of the interactions between biofilm-developed MPs as vectors and contaminants in aquatic environments.