Microplastic contamination in the mangroves of Piraquê-Açu and Piraquê-Mirim rivers, Aracruz (Brazil): An analysis in sediment, water, and biota

Mangroves are transitional ecosystems between terrestrial and marine environments, typical of tropical and subtropical regions. They contribute to socio-economic development by providing fisheries resources, which are essential for income generation and a significant source of animal protein. Thus, the consumption of marine organisms, particularly contaminated bivalves, represents a potential route for human exposure to microplastics (MPs). This study evaluated the presence, spatiotemporal distribution, and characterization of microplastics in sediment, surface water, and two bivalve species used for human consumption. Samples were collected from five distinct sites across the Aracruz mangrove (ES) to ensure a comprehensive representation of the study area. A total of 7806 microplastic particles were detected in the analyzed matrices, with the highest concentrations found in sediments, corroborating existing literature that identifies sediments as sinks for MPs. Filament-type microplastics predominated in all matrices, aligning with previous studies that report this form as prevalent in mangrove sediments. Blue microplastics were the most frequently observed across all matrices, potentially associated with discarded or abandoned fishing gear, a common practice in fishing zones. Crassostrea rhizophorae exhibited a higher concentration of MPs compared to Mytella strigata. Analysis of dry and wet periods revealed higher MP concentrations during the dry season, potentially explained by reduced dilution and increased accumulation of pollutants, while rainy seasons promoted MP transport to larger water bodies. A positive correlation between MPs in bivalves and those in surface water suggests that waterborne MPs are a significant contamination source for filter-feeding organisms.