Microplastic fibres in Pacific sand lance (Ammodytes personatus) burying habitats in the Strait of Georgia, British Columbia, Canada

The ingestion of Microplastic fibres (MF) by forage fish is of growing concern, as these MF have the potential to inhibit ingestion of nutrients, as well as accumulate and magnify at higher trophic levels. In the Strait of Georgia (SoG) on the Pacific Coast of Canada, such accumulation could be significant to the Pacific sand lance (PSL) (Ammodytes personatus), a key food source for marine predators such as Pacific salmon, seabirds, and marine mammals. The Pacific sand lance lacks a swim bladder and must bury in shallow low silt, medium coarse sand patches, and these sedimentary habitats may have high MF concentrations. This research assesses MF concentrations in PSL shallow subtidal burying habitats. Seafloor sediment samples were collected in Spring-Fall 2017, using a Van Veen grab sampler. Samples were collected at distances ranging from ~850 m to 20 kilometers from shore and effluent discharge pipes, and water depths ranging from 5 m to 100 m below the surface. MF concentrations were determined from 112 sediment samples in the laboratory using density extraction methods, while controlling for contamination. We found significantly higher concentrations of MF in suitable PSL burying habitat than in not suitable PSL habitat. Highly suitable PSL habitat had an average of 4.6 MF 10 g-1 and a median of 2.3 MF 10 g-1. A Kruskal Wallis test revealed that these values were significantly greater than in samples located in non-suitable PSL habitat, which had an average of 1.2 MF 10 g-1 and a median of 0.3 MF 10 g-1 (p = 3.5x10-5, 0-15 fibres 10 g-1). Additionally, we observed higher concentrations in shallow water depths (40 m). Congruently, we found distance from estuaries and sewage outflows, as well as proportion of very fine sand in sediment, to be related to MF concentration in seafloor sediment in the SoG. The high concentrations of MF in suitable PSL habitat found in this study could potentially have implications for PSL, such as MF ingestion and the consequent inability to digest organic foods due to the blockage of the digestive tract by MF.