Variability of microplastic abundances and their associated microbial communities in an urbanized coastal area. Microplastics pollution and the characterization of the microbial plastisphere

In 2018, we collected floating microplastics (< 5 mm) at three stations in the Gulf of Naples in January and July, comparing concentrations, polymer composition and characterizing attached microbial communities by Scanning Electron Microscopy (SEM) and Illumina 16S rDNA amplicon sequencing. Microplastics were mostly represented by Polyethylene (PE) in both seasons and were more concentrated in July than in January (3.13 vs 1.45 mp/m3 on average). Diatoms and bacteria were the most abundant microbes on microplastics, with different densities and components than free-living counterparts. PE-attached microbes appeared to be colonized by different microbial communities as the season changes, with Flavobacteriaceae, Saprospiraceae and Rhodobacteraceae bacteria dominating in both seasons but in different percentages and with very little overlap in terms of OTUs.