Use of sediment dwelling bivalves to biomonitor plastic particle pollution in intertidal regions; A review and study

We explore the possibility of using the varnish (Nutallia obscurata) and Manila (Venerupis philippinarum) clams as biomonitors of microplastics (MPs) pollution. A short review is first provided on the use of bivalves for biomonitoring MPs in aquatic ecosystems. From the conclusions drawn from our review we determine if the sediment dwelling varnish and Manila clam could possibly be good choices for this purpose. We sampled 8 intertidal sites located within two distinct regions of coastal British Columbia, Burrard Inlet (5 sites) and Baynes Sound (3 sites). Each intertidal region had its own particular use; within Burrard Inlet, BMP a heavily used marine park, CP, EB, J, and AP, popular local beaches, and within Baynes Sound, Met and NHB, two intertidal regions heavily exploited by the shellfish industry and RU an intertidal region with limited aquaculture activity. Microfragments were recovered from bivalves collected from all intertidal regions except for AP. Microspheres were recovered primarily from bivalves sampled from Baynes Sound at NHB where high numbers of spheres within sediments had previously been reported. BMP and Met had the highest number of particles present within individual clams which were predominantly high density polyethylene (HDPE) and a polypropylene composite (PPC). Both polymers are extensively used by the shellfish industry in all gear types, as well as in industrial and recreational marine activities. The spatial distribution of recovered MPs was indicative of the anthropogenic use of the intertidal region suggesting these bivalves, for microfragments and microspheres, may be suitable as biomonitors and could prove to be useful tools for determining whether reduction policies for plastics use are having a positive effect on their release into marine environments.