Abstract The coastal environment is a critical interface for monitoring plastic pollution. This study investigated microplastics (MPs, < 5 mm) and mesoplastics (MePs, 5–25 mm) in Praia Grande, São Francisco do Sul (SC State, Brazil), using stereomicroscopy and ATR-FTIR spectroscopy. Two sites with contrasting urbanization and tourism levels were assessed. Area #1, the more urbanized site, exhibited higher concentrations of MPs (70.44 particles·m⁻ 2 ) and MePs (25.11 particles·m⁻ 2 ) than Area #2 (19.11 MPs·m⁻ 2 ; 6.67 MePs·m⁻ 2 ). Morphological analysis revealed predominance of fragments in Area #1 and fibers (MPs) or foam (MePs) in Area #2. White, blue, and translucent particles were most abundant, while polymer identification highlighted the dominance of polyethylene, polypropylene, and styrene-butadiene copolymer, reflecting both global production patterns and local anthropogenic inputs. Sediment granulometry and hydrodynamics emerged as primary drivers of plastic retention, modulated by urbanization and tourism. Positive correlations between MePs and MPs indicate that MePs act as transitional reservoirs, contributing to secondary microplastic formation. These findings emphasize the hierarchical interplay of physical and anthropogenic factors in shaping coastal plastic distribution and provide a process-based framework to inform monitoring and management strategies.
Lopes-Ricardo et al. (2026) studied this question.