From categories to producers: Dual regulatory and Anthropocene-based classification of macrolitter on an uninhabited...

Marine macrolitter accumulation on islands provides a sensitive indicator of regional transport processes and production-consumption dynamics. In this study, coastal macrolitter assemblages were assessed on Isla Arena, a small uninhabited island in the Colombian Caribbean, using an integrated analytical framework that combines standardized regulatory monitoring (Joint List of Litter Categories) with the Anthropocene Taxonomy of Plastic Litter (ATPL). A total of 830 macrolitter items were collected across 779 m² during a single survey campaign, corresponding to a mean density of 1.07 items·m^-2, comparable to values reported for inhabited island systems worldwide. Plastics dominated the assemblage (>95%), with food consumption-related items prevailing. Plastic beverage bottles alone accounted for nearly 80% of all recorded macrolitter, indicating strong functional simplification. Classification based on the Joint List effectively characterized material composition and dominant use patterns but provided limited resolution regarding producer diversity. Application of ATPL revealed heterogeneity at producer, brand, and product levels within standardized item categories; however, producer or geographic origin could be confidently assigned to only 28% of plastic items due to environmental degradation and conservative visual identification criteria. For identifiable items, attribution indicated dominance by a limited number of corporate actors, primarily regional beverage producers. Although the study is based on a single island and one sampling campaign, the dual-classification approach demonstrates added analytical resolution relative to regulatory categories alone. The results suggest that Isla Arena functions as a convergence and retention zone for marine litter rather than a primary source area. The proposed framework preserves regulatory comparability while offering an expanded perspective for source-sensitive and responsibility-oriented interpretation in island and coastal environments.