Investigating the Presence and Trophic Transfer of Microplastics in Ex- and In-Situ North American Otters Through Scat and Diet 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 (Enhydra lutris) and North American river otters (Lontra canadensis) 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. 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

Zoop to poop: assessment of microparticle loads in gray whale zooplankton prey and fecal matter reveal high daily consumption rates

The ocean continues to be a sink for microparticle (MP) pollution, which includes microplastics and other anthropogenic debris. While documentation of MP in marine systems is now common, we lack information on rates of MP ingestion by baleen whales and their prey. We collected and assessed MP loads in zooplankton prey and fecal samples of gray whales (Eschrichtius robustus) feeding in coastal Oregon, USA and produced the first estimates of baleen whale MP consumption rates from empirical data of zooplankton MP loads (i.e., not modeled). All zooplankton species examined were documented gray whale prey items (Atylus tridens, Holmesimysis sculpta, Neomysis rayii) and contained an average of 4 MP per gram of tissue, mostly of the microfiber morphotype. We extrapolated MP loads in zooplankton prey to estimate the daily MP consumption rates of pregnant and lactating gray whales, which ranged between 6.5 and 21 million MP/day. However, these estimates do not account for MP ingested from ambient water or benthic sediments, which may be high for gray whales given their benthic foraging strategy. We also assessed MP loads in fecal samples from gray whales feeding in the same spatio-temporal area and detected MP in all samples examined, which included microfibers and significantly larger morphotypes than in the zooplankton. We theorize that gray whales ingest MP via both indirect trophic transfer from their zooplankton prey and directly through indiscriminate consumption of ambient MPs when foraging benthically where they consume larger MP morphotypes that have sunk and accumulated on the seafloor. Hence, our estimated daily MP consumption rates for gray whales are likely conservative because they are only based on indirect MP ingestion via prey. Our results improve the understanding of MP loads in marine ecosystems and highlight the need to assess the health impacts of MP consumption on zooplankton and baleen whales, particularly due to the predominance of microfibers in samples, which may be more toxic and difficult to excrete than other MP types. Furthermore, the high estimated rates of MP consumption by gray whales highlights the need to assess health consequences to individuals and subsequent scaled-up effects on population vital rates

Hold the Plastic, Please: An Investigation of Sea Otter Exposure to Microparticles and Microplastics Using Scat and Diet Analysis

Sea otters act as valuable indicators of ecosystem health and consume prey items that contain anthropogenic microparticles, including microplastics. Microplastic ingestion can exert a wide range of deleterious effects depending on the organism and plastic type. We investigated the ingestion of microparticles by wild sea otters (Enhydra lutris) in Alaska and those housed at the Seattle Aquarium by assessing the presence and abundance of microparticles in scat samples. We also analyzed diet items of captive otters to evaluate the role trophic transfer has in microparticle exposure for these individuals. Sample processing included digestion of organic material with potassium hydroxide, a density separation using a hypersaline solution, and confirmation of potential plastics with µFTIR spectroscopy. Microparticles were found in 95% and 91% of wild and captive sea otter scats, respectively, and 100% of diet samples. There were no differences between study sites in the particles per gram of wild sea otter scat. Of the total particles confirmed with µFTIR spectroscopy, 98.3% were of anthropogenic origin, and an average of 26.2% ± 6.2% were synthetic. There was also no difference in the proportion of particles identified as synthetic between study sites. This analysis demonstrates that sea otters are ingesting microplastics in wild and captive settings, and that trophic transfer likely contributes to this ingestion. It also provides information on the current level of microplastic exposure to populations of captive and wild sea otters using a non-invasive method, which may be beneficial for understanding sea otter population health. Future studies focusing on additional analysis of wild scats and examination of intestinal tracts of beached sea otters would build on the findings of this work

Zoop to poop : assessment of microparticle loads in gray whale zooplankton prey and fecal matter reveal high daily consumption rates

The ocean continues to be a sink for microparticle (MP) pollution, which includes microplastics and other anthropogenic debris. While documentation of MP in marine systems is now common, we lack information on rates of MP ingestion by baleen whales and their prey. We collected and assessed MP loads in zooplankton prey and fecal samples of gray whales (Eschrichtius robustus) feeding in coastal Oregon, USA and produced the first estimates of baleen whale MP consumption rates from empirical data of zooplankton MP loads (i.e., not modeled). All zooplankton species examined were documented gray whale prey items (Atylus tridens, Holmesimysis sculpta, Neomysis rayii) and contained an average of 4 MP per gram of tissue, mostly of the microfiber morphotype. We extrapolated MP loads in zooplankton prey to estimate the daily MP consumption rates of pregnant and lactating gray whales, which ranged between 6.5 and 21 million MP/day. However, these estimates do not account for MP ingested from ambient water or benthic sediments, which may be high for gray whales given their benthic foraging strategy. We also assessed MP loads in fecal samples from gray whales feeding in the same spatio-temporal area and detected MP in all samples examined, which included microfibers and significantly larger morphotypes than in the zooplankton. We theorize that gray whales ingest MP via both indirect trophic transfer from their zooplankton prey and directly through indiscriminate consumption of ambient MPs when foraging benthically where they consume larger MP morphotypes that have sunk and accumulated on the seafloor. Hence, our estimated daily MP consumption rates for gray whales are likely conservative because they are only based on indirect MP ingestion via prey. Our results improve the understanding of MP loads in marine ecosystems and highlight the need to assess the health impacts of MP consumption on zooplankton and baleen whales, particularly due to the predominance of microfibers in samples, which may be more toxic and difficult to excrete than other MP types. Furthermore, the high estimated rates of MP consumption by gray whales highlights the need to assess health consequences to individuals and subsequent scaled-up effects on population vital rates

Quantitative assessment of visual microscopy as a tool for microplastic research: Recommendations for improving methods and reporting.

Microscopy is often the first step in microplastic analysis and is generally followed by spectroscopy to confirm material type. The value of microscopy lies in its ability to provide count, size, color, and morphological information to inform toxicity and source apportionment. To assess the accuracy and precision of microscopy, we conducted a method evaluation study. Twenty-two laboratories from six countries were provided three blind spiked clean water samples and asked to follow a standard operating procedure. The samples contained a known number of microplastics with different morphologies (fiber, fragment, sphere), colors (clear, white, green, blue, red, and orange), polymer types (PE, PS, PVC, and PET), and sizes (ranging from roughly 3-2000 μm), and natural materials (natural hair, fibers, and shells; 100-7000 μm) that could be mistaken for microplastics (i.e., false positives). Particle recovery was poor for the smallest size fraction (3-20 μm). Average recovery (±StDev) for all reported particles >50 μm was 94.5 ± 56.3%. After quality checks, recovery for >50 μm spiked particles was 51.3 ± 21.7%. Recovery varied based on morphology and color, with poorest recovery for fibers and the largest deviations for clear and white particles. Experience mattered; less experienced laboratories tended to report higher concentration and had a higher variance among replicates. Participants identified opportunity for increased accuracy and precision through training, improved color and morphology keys, and method alterations relevant to size fractionation. The resulting data informs future work, constraining and highlighting the value of microscopy for microplastics