Biofilm facilitates metal accumulation onto new plastic pellets in aquatic environments

Plastic debris in aquatic environments can accumulate ions from the surrounding water, potentially altering the fate of trace metals in these ecosystems. Mechanisms driving this process are poorly understood, and may be attributed to organic matter fouling the plastic's surface. In this study, two types of pristine plastic pellets as well as glass pellets were suspended in the San Francisco Bay and biomass and metal accumulation were measured at various time intervals up to 28 days. At each time point, increasing biomass was positively correlated with metal accumulation on plastic pellets. Glass accumulated significantly higher levels of Zn compared with plastic materials regardless of biofilm growth. For other metals that showed an affinity for glass, the importance of biomass as a predictor of metal concentration increased and the differences between glass and plastic decreased over time and as biofilm increased. Future studies should account for the effect of biofilms when estimating contaminant sorption and desorption potential on plastic debris relative to other types of debris materials.