Relathionships Between Nanoplastic Contamination and Biochemical Properties of Biofilms in the Saint-Lawrence River

Biofilms are usually found on rocky surfaces in streams, rivers and lakes, which are under the influence of multiple pollution types, including nanoplastics (NPs). The purpose of this study was to examine both the influence of anthropogenic activity (pollution) on the occurrence of NPs and the plasticizer dibutylphthalate (DBP) on the functional characteristics of biofilms. Biofilms were collected on rocks at different sites with a gradient of anthropogenic activities, and were analyzed for DBP and NPs using a plasmonic gold nanosensor. Their functional properties, such as proteins, lipids, viscosity, chlorophyl a/b, esterase, aldehydes (oxidative stress) and polyurethane biodegradation index (BDI), were assessed as well. The results revealed that biofilms downstream a large city and agricultural sites contained higher amounts of DBP and NPs. The BDI and esterase activity, involved in the degradation of plastic esters, were dampened at sites under anthropogenic pollution, suggesting a negative impacts on plastic biodegradation. The levels in viscosity, lipids and proteins were also affected in biofilms from anthropogenic sites, and showed signs of oxidative stress. It is concluded that biofilms at polluted sites are contaminated by plastic related compounds and display reduced capacity to degrade plastic esters.