Microplastic Distribution and Abundance in Mussels Along the California and Oregon Coasts

Inez Mangino, United States, Britta Baechler, Portland State University, Portland, OR, United States, Sarah A Gravem, Oregon State University, Corvallis, OR, United States, Elise F Granek, Portland State University, Environmental Science & Management, Portland, OR, United States, John Dickens, Undergraduate Researcher, United States, Susanne M Brander, Oregon State University, Department of Environmental and Molecular Toxicology, Corvallis, United States and Laurel Field, Faculty Research Assistant, United States
Plastic contamination in the world’s oceans is a considerable threat to the health of the environment, marine ecosystems and humans. In this study, the distribution and quantity of microplastics amongst mussels (Mytilus californianus)was investigated. Mussels were collected and outplanted for a year at 9 sites along the Oregon and California coasts. Suspected microplastics were detected in all but one of the sampled mussels (n=10 per site). The number of suspected items observed across all sites varied from 2.4 to 5.1 items/individual. Across all sites, fibers made up 59% of all detected microplastics. The most common size class of microplastics ranged from 51-100µm. A significant difference in microplastic distribution between three of the nine sampling sites was observed, indicating a potential for differences in microplastic levels between sites due to land-use or ocean currents. Future analysis of chemical composition through micro-Fourier-transform infrared spectroscopy (FT-IR) will be conducted on the isolated microplastics from this study. This research provides an environmentally relevant analysis of microplastics found in mussels.Our results suggest that relative microplastic levels are similar to existing studies in bivalves. Future studies should further investigate sites with elevated microplastic internalization in mussels compared to others, particularly those that are relatively protected from run-off or other direct inputs of pollution, toidentify potential oceanographic drivers.