No microplastics detected in the first assessment of Atlantic walrus stomachs from Nunavut, Canada

As plastic pollution continues to persist at a global level, the Arctic has drawn increased research interest as a possible sink for marine pollutants. Plastic and microplastics are highly durable and can be transported across vast distances. To date, only a handful of studies have directly assessed microplastics in Arctic mammals. In Canada, it is still unclear whether they show a concrete propensity for microplastic retention and ingestion. Atlantic walruses ( Odobenus rosmarus rosmarus (Linnaeus, 1758)) are economically and culturally important for Inuit and are key predators in Arctic marine ecosystems. Here, we present the first assessment of microplastic pollution in Canadian walruses and the first gastrointestinal assessment of microplastic in walruses globally. Since microplastics accumulate in benthic sediment and animals, we expected that walruses may ingest and retain microplastic contaminants when sifting in search of prey or when eating contaminated bivalves and invertebrates. We detected no microplastics ≥80 µm in our evaluation of 36 walruses from five communities in NU, Canada. Our results suggest that walruses in this region do not retain microplastic particles ≥80 µm in their stomachs, which is consistent with findings in other pinnipeds that have been evaluated in Arctic Canada.