Differentiation of bacterial communities on five common plastics after six days of exposure to Caribbean coastal waters

Plastic pollution in coastal areas, particularly in subtropical and tropical regions, remains a pervasive environmental issue. Marine plastic debris provides an artificial surface that rapidly accumulates a dynamic microbial biofilm upon entering the marine ecosystem. Especially the early stages of colonization are critical in shaping the microbial community. This study investigates the early microbial colonization, in less than a week, on five different plastic polymers in Caribbean coastal waters through 16S rRNA gene amplicon sequencing. We discovered shared bacterial taxa among the various plastic polymers and sampling timepoints, with dominant orders being Flavobacteriales, Rhodobacterales, Rhizobiales, and Pseudomonadales. Statistical analysis confirmed significant differences in community composition between the two sampling points, with polystyrene exhibiting a distinct microbial community on day 6 compared to polyethylene, polypropylene, and nylon. We found the same for polyethylene compared to nylon and polyethylene-terephthalate. Further examination identified 47 genera responsible for these differences, primarily belonging to the phyla Proteobacteria and Bacteroidota. Our data indicate an influence of both environmentally related stochastic processes and plastic-related specific factors during early colonization. Interestingly, we noticed an increase in the relative abundance of hydrocarbon and potentially plastic-degrading bacteria (PDB) from 12.4 to 34.5% between the first and sixth day, suggesting their vital role in shaping the epiplastic community. Notably, some identified PDB have been reported to degrade the specific polymers studied, thus the monitored increase in relative abundance supports their role in plastic degradation. However, more research is required to fully understand their functioning and potential role in the epiplastic community. Our study provides insights into the prokaryotic colonization of marine plastics in the Caribbean basin, where to date studies have been limited despite high pollution rates.