Investigating the Presence and Trophic Transfer of Microplastics in Ex- and In-Situ North American Otters Through Diet and Scat Analysis

While an increasing number of studies have examined the presence and effects of microplastics in aquatic organisms like invertebrates and fish, there is still a dearth of knowledge about their impact on mammals in higher trophic levels. Both sea and river otters act as valuable indicators of ecosystem health and consume prey items that have been shown to contain microplastics. As such, we are investigating the ingestion of microplastics by sea otters and North American river otters in the North Pacific using scat. Our study includes samples from ex situ and in situ individuals and also analyzes otter prey items for microplastic particles in order to evaluate the role trophic transfer may have in microplastic ingestion by otters. Additionally, we are examining archived river otter scat samples from the same site over multiple years to observe how the presence of microplastics in otter scat may have changed over time. The fecal and prey analysis consists of potassium hydroxide digestion, sieving, vacuum filtration, observation with a microscope, and FTIR spectroscopy. This analysis could provide opportunities to understand the current level of microplastic ingestion by wild sea and river otters using a non-invasive method, which may be beneficial to understanding sea and river otter population health. Beyond the impacts this knowledge could have for North American otter species, the results could provide information about the exposure of other species to microplastics that share ecosystems of interest.