Microplastics Analysis and Quantification of Benthic Sediments of the Salish Sea

Plastic marine debris presence in marine ecosystems is becoming a growing issue. Microplastics are any polymer with long axes between 0.33 to 5 mm. This material is an emerging concern because they are persistent in the environment and can build up in bed sediments, potentially creating sinks in important ecosystems such as the Salish Sea. This study will focus on determining the location, abundance, and types of microplastics in Salish Sea sediments by analyzing sediment samples provided by the Washington State Department of Ecology’s Puget Sound Ecosystem Monitoring Program. This research team processed and analyzed samples from 22 stations from 2014 to 2018. The laboratory methodology used for these samples included chemical processing, wet sieving, peroxide oxidation, and density separation, followed by manual visual inspection and extraction of microplastics under a microscope. Microplastics were identified by type, color, length of long axe, and number. In the last six years, microplastics were found at all stations except for one sample in 2017. The average abundance was 3,000 mp/m2 and the highest abundance was found at a station in Sinclair Inlet which had 27,000 mp/m2. This data showed a decrease in microplastics over time, yet this decrease was not statistically significant. In order to gain more understanding of the impacts of microplastics on the Salish Sea’s benthic communities, continued monitoring and additional stations are needed. This preliminary research could contribute to future research on microplastic mitigation and restoration efforts in estuaries like the Puget Sound.