Presence and characteristics of plastics and microplastics on the seabed of the western English Channel

Little is known about the presence, distribution, origins and characteristics of plastic litter and microplastics on the ocean floor. In this study, plastics trawled from the bed of the western English Channel have been categorised and analysed by a variety of optical and spectroscopic techniques. A total of 90 plastic samples were classified, in descending order of abundance, as food-drink packaging, unknown, homeware, military and fishing. Most samples showed varying degrees of weathering (e.g., discolouration, distortion, cracking, fragmentation) and were visibly fouled by calcareous deposits. The majority of samples were constructed of polymers of negative buoyancy (e.g., polyamides, polyethylene terephthalate and polyvinyl chloride) with one sample identified as positively buoyant (polyethylene). Additives and pigments among the samples included asbestos, glass fibres, Cd-, Pb- and Sn-based stabilisers, Ba- and Ti-based compounds, and antifouling residues. Microscopy revealed the ubiquity of microfibres that were often strongly adhered to the plastic or fouled surfaces and whose polymeric compositions did not match those of the host material. This observation is attributed to encounters of microfibres with a slimy, accruing biofilm on the plastic and suggests that synthetic fibres are highly abundant and persistent in suspension close to the seafloor. The impacts of these fibres are unknown and warrant further investigation.