A continental-scale analysis of benthic litter in marine and freshwater habitats of the Americas using standardized citizen science data

This study presents a continental-scale assessment of benthic macro-litter pollution across marine and freshwater environments in North America, Latin America and the Caribbean, based on standardized data collected by volunteer scuba divers through a global citizen science initiative. Latin America and the Caribbean exhibited a significantly higher density of marine plastic and Single-Use Plastic (SUP), mainly objects for food and beverage consumption, compared to North America. In that region, metals were the most dominant in freshwater environments (42 %), whereas plastics prevailed in marine habitats (44 %). Across both, top-ten litter items accounted for more than 68 % of the total litter, with fishing lines representing a major source of benthic debris. Notably, fishing gear accounted for about 40 % of total marine litter in NA. Our findings underscore the critical role of the fishing sector in marine litter composition and the need for targeted regulatory actions such as stronger regional bans on SUPs and the introduction of extended producer responsibility schemes (as promoted in the European Plastics Strategy). This study also demonstrates the potential of well-structured citizen science initiatives to provide valuable quantitative data for long-term monitoring and to support evidence-based policy development for coastal pollution mitigation.