Using long-term citizen science data to distinguish zones of debris accumulation.

Studies show that a driver of coastal debris is the rate between debris deposition and resuspension; however, the influence of beach zone topography on the distribution of debris remains poorly understood. Using five years of marine debris data collected by the COASST citizen science program, we explored the spatiotemporal trends in debris abundance within two regions of the United States Pacific Northwest and investigated whether higher debris loads are associated with beach zones that have a higher propensity to trap debris. We found that beaches with larger wood zones had higher debris loads, adding to the growing evidence that backshore areas of beaches act as sinks for debris. Higher debris loads were also associated with beaches that had larger wrack zones suggesting that onshore transport from the marine reservoir is a dominant source of debris. This study provides a long-term baseline of marine debris which managers could use to inform source reduction interventions. • More debris was found on beaches with larger wood and wrack zones. • Plastic was the most observed material annually in each region. • Debris declined in both the Puget Sound and the WA-OR coast region. • Highest loads of debris were observed in Spring and lowest loads in Autumn. [ABSTRACT FROM AUTHOR]