Temporal trends in anthropogenic marine macro-debris and micro-debris accumulation on the California Channel Islands

Accumulation of anthropogenic marine debris on shorelines is an issue global concern, even impacting areas that are remote, uninhabited, or have protected area status. On islands in Southern California, USA, within the boundaries a National Park and Marine Sanctuary, we collected macro-debris beaches assessed micro-debris beach sediment seasonally between 2016-2020. Macro-debris (>5mm) was from seven two California Channel Islands sites mainland. We both number items total mass debris. Composition dominated by plastics, particularly fragmented hard foamed plastics food packaging. A substantial quantity lost discarded fishing gear collected, with most fishery-related found at historically highest spiny lobster effort. The initial density ranged 0.01-0.13 m -2 0.01-0.02 kg . Mean accumulation rates were strongly site-dependent 0.03-0.34 yr -1 0.01-0.05 , tended to be fall winter months. Anthropogenic (<5mm) all sites. Micro-debris had no statistically significant relationship items, plastic items. There were, however, relationships mass. compared rate during season (October-March) for years 2017 2020. differed significantly among sites, apparent declines over time, likely reflecting declining effort fishery trap-limit regulations implemented 2017-2018 season. Our assessment Island has provided detailed information types patterns accumulation. Unfortunately, remoteness direct human impact protected-area status does not protect these habitats against onslaught litter. Assessments critical identify sources, inform policy support efforts reduce litter vital coastal ecosystems.