Integrated assessment of macro- and microplastic pollution in mangrove and coastal estuarine ecosystem of the Can Gio Biosphere Reserve, Vietnam: abundance and mass spatial distribution, polymer composition and driving factors

Ecological and socio-economic significance of mangrove-estuarine ecosystems has been widely acknowledged, yet they have increasingly threatened by plastic pollution driven by complex hydrodynamics and anthropogenic pressures that have promoted plastic accumulation. This study presented an integrated assessment of macro-mesoplastic (MMPs) and microplastic (MPs) pollution in mangrove-estuarine ecosystem of the Can Gio Biosphere Reserve, Vietnam, integrating multiple environmental compartments, including MMPs accumulation on mangrove surface, MPs contamination in surface sediments, and bivalves. Field surveys were conducted across nine sites representing mangrove core, buffer, and coastal estuarine zones. The MMPs (> 2.5 cm) and MPs were analyzed in term of abundance, mass, shape, color and polymer composition. The MMPs exhibited pronounced spatial heterogeneity, with average abundance and mass of 1.59 ± 1.37 items/m2 and 20.17 ± 10.02 g/m2, respectively. Total MMPs mass within the study was estimated at approximately 132 tons, highlighting substantial surface accumulation. The MPs were ubiquitous across all matrices, dominated by fibers and fragments composed primarily of polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP), with average abundance and mass of 74.74 ± 47.46 items/kg and 47.94 ± 42.70 mg/kg in sediments, and 0.352 ± 0.04 items/individualand 0.054 ± 0.018 items/g wet tissue in bivalves. Biota-sediment ratios (BSR) indicated variable relative enrichment of microplastics in bivalves, reflecting effective bioindicators for monitoring microplastic contamination and assessing human exposure via seafood consumption. Principal component analysis (PCA) identified population and river morphology as key drivers shaping plastic distribution patterns. By integrating macro-mesoplastics, microplastics, and biological exposure, this study provided new insights into plastic partitioning in tropical mangrove-estuarine ecosystems and supported the development of sustainable management strategies.