Continental patterns in marine debris revealed by a decade of citizen science

Anthropogenic marine debris is a persistent threat to oceans, imposing risks to ecosystems and the communities they support. Whilst an understanding of marine debris risks is steadily advancing, monitoring at spatial and temporal scales relevant to management remains limited. Citizen science projects address this shortcoming but are often critiqued on data accuracy and potential bias in sampling efforts. Here we present 10-years of Australia's largest marine debris database -the Australian Marine Debris Initiative (AMDI), in which we perform systematic data filtering, test for differences between collecting groups, and report patterns in marine debris. We defined five stages of data filtering to address issues in data quality and to limit inference to ocean-facing sandy beaches. Significant differences were observed in the average accumulation of items between filtered and re-maining data. Further, differences in sampling were compared between collecting groups at the same site (e.g., government, NGOs, and schools), where no significant differences were observed. The filtering process re-moved 21% of events due to data quality issues and a further 42% of events to restrict analyses to ocean-facing sandy beaches. The remaining 7275 events across 852 sites allowed for an assessment of debris patterns atan un-precedented spatial and temporal resolution. Hard plastics were the most common material found on beaches both nationally and regionally, consisting of up to 75% of total debris. Nationally, land and sea-sourced items accounted for 48% and 7% of debris, respectively, with most debris found on the east coast of Australia. This study demonstrates the value of citizen science datasets with broad spatial and temporal coverage, and the im-portance of data filtering to improve data quality. The citizen science presented provides an understanding of debris patterns on Australia's ocean beaches and can serve as a foundation for future source reduction plans. (c) 2021 Elsevier B.V. All rights reserved.