Colonization Is Highly Dynamic in Early Microplastic-Associated Biofilms as Well as on Field-Collected Microplastics.

Microplastics are ubiquitous in aquatic ecosystems and provide a habitat for biofilm-forming bacteria. The genus , which includes potential pathogens, was detected irregularly on microplastics. Since then, the potential of microplastics to enrich (and serve as a vector for) has been widely discussed. We investigated abundance and operational taxonomic unit (OTU) composition on polyethylene and polystyrene within the first 10 h of colonization during an in situ incubation experiment, along with those found on particles collected from the Baltic Sea. We used 16S rRNA gene amplicon sequencing and co-occurrence networks to elaborate the role of within biofilms. Colonization of plastics with was detectable after one hour of incubation; however, numbers and composition were very dynamic, with a more stable population at the site with highest nutrients and lowest salinity. Likewise, abundances on field-collected particles were variable but correlated with proximity to major cities. was poorly connected within biofilm networks. Taken together, this indicates that is an early colonizer of plastics, but that the process is undirected and independent of the specific surface. Still, higher nutrients could enhance a faster establishment of populations. These parameters should be considered when planning studies investigating on microplastics.