Characterization of freshwater macroplastic-associated bacterial communities using 16S rDNA sequencing

Abstract

Plastic pollution has become a major concern across all ecosystems, especially in freshwater environments. Freshwater bodies such as rivers, lakes, and streams serve as hotspots for accumulation of plastic waste, providing an interface for colonization and further succession of a self-sustaining microbial consortium known as the "plastisphere". In this study, plastisphere communities were sampled from individual and rafted, purposefully deployed and pre-existing polyethylene (PET), polypropylene (PP), polystyrene (PS) substrates during June, July and August 2025 at Arcadia Lake, Edmond, OK, USA. The microbial communities collected were further characterized using 16S rDNA metabarcoding. Wood substrates were also sampled to represent naturally occurring microbial communities. Our research supports primary influences of substrate type and sampling time on the progression of the plastisphere. Alpha diversity analysis revealed that PET and PP showed similar levels of microbial diversity while PS was similar to wood. Family Leptolyngbyaceae was the most abundant family on all substrates across the sampling duration. Substrate preference was observed in families Rhodobacteraceae and Nostocaceae for PET and PP when compared to PS and wood. Additionally, Cyanobiaceae and Deinococcaceae were abundant on PS compared to other plastic substrates. Wood was enriched with Beijerinckiaceae for all three months. Across the sampling period, the abundance of Leptolyngbyaceae on PET and PP was highest in June and lowest in August while Nostocaceae was recovered to be abundant in July and August. Rhodobacteraceae was abundant in June on all the samples compared to June and July. Beta diversity analysis further supported our alpha diversity findings. Weighted UniFrac ANOVA analysis revealed significant results for individual factors such as substrate, collection date and combination factors substrate+collection date and substrate+single/rafts. Additionally, ANOVA analysis for combination factor substrate+artificial/naturals was recovered to be significant for all beta diversity measures including Bray-Curtis, Jaccard, UniFrac and wUniFrac. Finally, PERMANOVA analysis demonstrated significant results for substrate and collection date (time) establishing the importance of time in shaping plastisphere microbial communities along with substrate. Although numerous studies have shown the influence of a variety of factors on plastisphere succession, there is still a need to characterize the "global" plastisphere community while simultaneously determining the driving factors involved in shaping microbial succession among these communities. Abbreviations: PET-polyethylene terephthalate; PP-polypropylene; PS-polystyrene; ANOVA-analysis of variance; PERMANOVA- permutational multivariate analysis of variance.