Influence of biological, ecological, and anthropogenic factors on microplastic contamination in coastal fishes from Southeastern Brazil

Abstract Microplastics (MPs) are a pervasive environmental threat due to their persistence, bioavailability, and toxicity. In marine environments, MPs are widely distributed and ingested by fish, posing risks to human consumers. This study examined how ecological and anthropogenic factors—body size, water column position, seasonality, and human impact—influence MP concentrations in the muscle and digestive tissues of coastal fish from southeastern Brazil. We hypothesized that fish from more impacted environments would contain higher MP levels; that pelagic species would ingest more MPs due to particle buoyancy; and that ingestion would be higher in summer and in larger fish due to seasonal and size-related factors. Additionally, we hypothesized that MP loads would be higher in digestive tissues than in muscle, given limited translocation capacity. Four commercially important species ( Caranx crysos , Sardinella aurita , Menticirrhus americanus , and Micropogonias furnieri ) were collected from two bays with contrasting anthropogenic influences—Sepetiba (more impacted) and Ilha Grande (less impacted)—during summer and winter. Digestive tracts and muscle tissues were digested, vacuum-filtered, and analyzed using microscopy and micro-FTIR. MPs were detected in all species and in 83.1% of individuals, with blue microfibers predominating. Generalized linear mixed models revealed positive associations between MP ingestion and anthropogenic impact and season (summer), and a negative association with body size. No significant differences were observed between pelagic and demersal species or between tissues. Thus, MP contamination in coastal fishes from southeastern Brazil appears to be driven primarily by gradients of human impact and seasonality (with a peak in summer), rather than by habitat or tissue differences, indicating that MP monitoring and control programs should prioritize urbanized areas and periods of higher input/resuspension.