Nanoplastics & the marine microbial plastisphere Towards a better understanding of fate & impact

This thesis investigates the fate and impact of nanoplastics (plastic particles between 1 – 1000 nm) on the marine microbial plastisphere (the microbial biofilm that colonizes plastic surfaces). Central to this work are several key hypotheses: 1) nanoplastics interact dynamically with microbial biofilms in the plastisphere; 2) these biofilms modulate the environmental fate of nanoplastics; exposure to nanoplastics may alter microbial community composition and biofilm structure; and 3) the plastisphere may function as a sink for nanoplastics while facilitating the accumulation of plastic–associated contaminants, thereby influencing their persistence and mobility in marine systems.
Literature review highlighted how nanoplastics display distinct aggregation dynamics, often binding to organic matter, and how marine microbial communities of the plastisphere may become a dynamic hotspot for these interactions. Laboratory experiments revealed how a) polystyrene nanoplastics (PS NPs) do not significantly inhibit PHBH biodegradation extent, but may alter biofilm microbial community dynamics b) perfluoroalkyl carboxylic acid (PFCAs) leach from polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP) micro/nanoplastics (MNPs) in seawater to a different extent in the presence of a plastisphere bacterium compared to treatments without and c) fluorescent nanoplastics of varying morphologies synthesized via nanoprecipitation with selective staining can be differentiated once taken up by plastisphere–isolated protists. Altogether, this work demonstrates the complex role of microbial communities in mediating nanoplastic fate. The methodologies used here–such as utilizing natural microbial consortia, tracking functional endpoints, and employing environmentally relevant nanoplastic estimates–offer valuable tools for advancing nanoplastic research under more realistic marine conditions.