Spatio-temporal variability of beached macro-litter on remote islands of the North Atlantic

Highlights: • A total of 31439 items were collected on 42 beaches with an average density of 0.62 items m^-2 • 87% of all items were made out of plastic, 67% of those being plastic fragments. • Gravel beaches showed higher densities of marine litter when compared to rocky and sandy beaches. • The beaches with highest litter density have a southwest orientation, coinciding with prevalent wind direction. • Seasonal monitoring demonstrated a strong variability of litter input, partly correlated with wind exposure. - Abstract: Marine litter has been identified as one of the major environmental problems that oceans are currently facing. Worldwide efforts are being made to reduce the input of litter into the oceans, and projects aimed at monitoring their quantities are key to evaluate their success. This study, provide baseline information on the quantities of marine litter found on 42 beaches spread throughout the nine islands of the Azores archipelago, North Atlantic Ocean. A total of 31,439 items were collected throughout the archipelago with an average density of 0.62 ± 0.15 macro-litter items m⁻². Of this litter 87% were plastic and its majority (67%) plastic fragments. Six beaches were further monitored every three months for two years. Substrate type and wind exposure were important factors for explaining patterns of litter deposition. Our results highlight that marine litter have the tendency to accumulate in remote islands of the North Atlantic Ocean.