| Summary: | Microplastics (MPs, particles <5 mm) represent an emerging global environmental concern and has been detected in multiple aquatic species. Very little is known, however, about the presence of MPs in higher trophic level species, including cetaceans. Working in collaboration with Inuvialuit hunters from Tuktoyaktuk (Northwest Territories, Canada) and researchers from the Department of Fisheries and Oceans, entire stomachs and intestinal sub-sections were collected from seven beluga whales (Delphinapterus leucas) in 2017 (n=4) and 2018 (n=3) for examination. Microplastics were detected in the gastrointestinal tracts in every whale. Each whale contained an estimated 18 to 147 MPs in their GI tract with an average of 97 ± 42 per individual. FTIR-spectroscopy revealed over eight plastic polymer types, with nearly half being polyester. Dominant MP types were equally present, with fragments making up 51% and fibres 49%. The potential source of MPs to beluga via prey items was also determined by examining the GI tracts from five Arctic fish species belonging to the beluga food web (n=116). Species investigated included (Arctic cod (Boreogadus saida), saffron cod (Eleginus gracilis), Arctic cisco (Coregonus autumnalis) four-horn sculpin (Myoxocephalus quadricornis) and capelin (Mallotus villosus). Microplastics were found in 21% of prey. The fish that contained microplastics had a mean abundance of 1.42 ± 0.44 particles per individual and 85% of particles observed were fibres. Particle size and polymer types found in prey were similar to those found in beluga, suggesting that trophic transfer of MPs from prey to beluga may be occurring. The diversity of MP shapes and polymeric identities in all species investigated points to a complex source scenario, and ultimately raises questions regarding the significance and long-term exposure of this pollutant in these ecologically and culturally valuable species.
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