We summarize results of two independent studies on plastic pollution in the marine environment that overlap in time and space. One study evaluated the abundance of anthropogenic debris on 37 sandy beaches bordering the Salish Sea in Washington State while the other characterized plastic debris in surface waters of the Salish Sea and the Inside Passage to Skagway, Alaska. Both studies concluded that foam, primarily expanded polystyrene was the dominant pollutant. Plastic was found in surface waters the full length of the Inside Passage but was concentrated near harbors. At the wrack line, an average square meter of Washington’s 1180 km of sandy beaches in the Salish Sea had 61 pieces of anthropogenic debris weighing approximately 5 g. The total loading for the entire 1 m wide band is estimated to be 72,000,000 pieces and 5.8 metric tons. Most anthropogenic debris on beaches is generated within the region.
Wallace Davis III, Anne G. Murphy, Marine Pollution Bulletin, Volume 97, Issues 1–2, Pages 169–177, 15 August 2015