Biofilm Development\non Macroplastics along a Freshwater-Estuarine\nGradient with Attention to Diatom Assemblages

Plastic pollution poses a significant and persistent\nthreat to\nthe health and functioning of aquatic ecosystems worldwide. The development\nof microbial communities on freshwater macroplastics can affect nutrient\ncycling and facilitate biotic dispersal, while characterization of\nbiofilm assemblages can inform on residency time, pathways, and accumulation\npatterns of aquatic plastics. Polypropylene, poly(ethylene terephthalate),\nand polystyrene coupons were incubated in the River Great Ouse, UK\nfor 21 days at locations with increasing salinity. Biofilm abundance\nwas quantified using crystal violet staining and spectrophotometry,\nand community composition was characterized through scanning electron\nmicroscopy (SEM) image analysis. Here, we show how time, plastic type,\nand site impact biofilm development and composition, with special\nattention to diatoms, on aquatic plastics. Site was the most determinant\nfactor for biofilm abundance. However, we found no plastic-specific\nor site-specific assemblages of biofilm diatom communities. This study\nhighlights the stochastic nature of biofilm development on plastics\nin freshwater-estuarine systems as well as the factors that must be\nconsidered in dynamic aquatic environments, such as hydrological conditions\nof the site, that challenge simple community development models that\nhave been used for marine environments.