Vertical distribution of microplastics in Hood Canal and Main Basin, Puget Sound, Washington

Abstract

Microplastics have been an increasingly important pollutant and area of research over the past 50 years. Although microplastics threaten marine ecosystems in various ways, little is known about their sink, vertical distribution or role in estuaries. To address the lack of knowledge of the vertical distribution of microplastics in estuarine systems, this study collects and analyzes observational data across the water column in Puget Sound using a series of net tows. Microplastics were visually observed in all samples collected and the samples were quantified to concentrations at each depth. The highest microplastic concentration - 1.88x10 -4 g/m 3 - was found in Possession Sound while the most consistent vertical profile was found at Seabeck in Hood Canal, suggesting residence time is more likely a driving factor to vertical distribution than proximity to population centers. This study uses a novel approach to researching the vertical distribution of microplastics and therefore highlights the need for further research and awareness on the increasingly important issue of microplastics.