An assessment of microplastics in fecal samples from polar bears (<i>Ursus maritimus</i>) in Canada's North

We assessed the potential for plastic ingestion in polar bears ( Ursus maritimus (Phipps (1774))) using fecal analysis. Two method studies ensured our protocols could effectively recover and identify plastics in feces. First, microplastics (film, foam, or fragments) were intentionally introduced into a model organic matrix. Recovery rates (mean ± standard deviation) averaged 95.8 ± 14.7% ( n = 18) and were significantly affected by microplastic morphology but not digestion status. Second, microplastic fragments of polypropylene, polyethylene terephthalate, and polystyrene were intentionally introduced to polar bear feces. Recovery rates averaged 79.3 ± 21.6% ( n = 8) and Raman microscopy successfully identified all three polymers in 87.5% of samples. The main study then investigated the presence of microplastics in hunter-collected polar bear feces in the Canadian Arctic. Feces from the colons of hunted bears ( n = 15) and field scat ( n = 15) were collected through collaboration with Inuit communities. Polypropylene, polyethylene, and/or polyethylene terephthalate were detected in the feces of eight bears. Concentrations of microplastics in feces were, on average, less than 1 particle/g dry weight feces and at or near detection limits. Overall, this work suggests microplastic ingestion by Canadian polar bears may be low and demonstrates the utility of fecal sampling for community-based monitoring programs.