Assessing fiberglass particles in intertidal biofilm and sediments at an anthropogenically impacted estuary in Canada's west coast.

Fiberglass particles are anthropogenic micropollutants of emerging concern for marine-coastal ecosystems and biodiversity. To investigate the occurrence of fiberglass, samples of intertidal sediment and biofilm matrices were collected in 2020, 2023 and 2024 from mudflats on the anthropogenically influenced Cowichan Estuary in British Columbia, Pacific Canada. Samples were analyzed using density separation and extraction methods, stereomicroscopy, FTIR spectroscopy, and scanning electron microscopy (SEM 3 Explore and FE-SEM) to identify fiberglass particles. Fiberglass concentrations in sediments were observed across most sampling stations (frequency of occurrence: 64.3 % in 2020 and 96.15 % in 2023), ranging from 6 to 286 particles/kg dw, with the highest levels detected near a log transport channel and marinas of Cowichan Bay Village. Intertidal biofilm samples showed localized presence of fiberglass abundance, ranging from 30 to 62 particles/kg dw, particularly in areas near industrial, boat, and marina activity. The finding of trimellitic anhydride (1,2,4-benzenetricarboxylic anhydride) via FTIR and FE-SEM in biofilm samples as a potential tracer further corroborates fiberglass presence since this compound is a binder in glass fiber aggregates. Glass fiber fragments having a higher density than seawater were more prone to be deposited deeper in sediments rather than onto surface biofilm, constituting the top layer of 3-5 mm of surficial mudflats. These results highlight the need for better regulation of public access to slipways and commercial boat maintenance facilities, as well as improved waste and of end-of-life boat management practices, with mitigation efforts to minimize the release and further exposure and spread of fiberglass reinforced plastic micropollutants in aquatic environments.