Unravelling coastal plastic pollution dynamics along southeastern Australia: Insights from oceanographic modelling informed by empirical data

Marine plastic pollution poses a global environmental challenge, understanding dispersal patterns at management-relevant scales is required to inform effective actions. We combine high-resolution oceanographic modelling and particle tracking with empirical data from Australia's largest marine debris database to investigate plastic debris transport across southeastern Australia. Our results challenge the assumption that marine debris primarily originates from distant sources, revealing that source regions are predominantly confined within a 15-km coastal band, with 50% of the debris modelled only spending 8 days at sea, and originating (on average) 20-km away. A comparison of empirically-informed simulations with uniform seeding scenarios shows significant differences in the number and intensity of identified marine source hotspots of plastic debris across the coastal band. These findings emphasize the importance of local management strategies and demonstrate how integrating observational data with oceanographic modelling can enhance our understanding of marine debris dynamics, ultimately supporting more targeted pollution reduction efforts.