Differential Accumulation of Particulate Pollutants in Gills and Gastrointestinal Tracts in Sphoeroides Fish from Tropical and Subtropical Estuaries in Brazil

The widespread use of recyclable materials in contemporary society has led to the accumulation of pollutants in estuaries and marine ecosystems, with potential impacts on biodiversity. This study assessed the abundance and types of particulate pollutants in Sphoeroides fish across two Brazilian estuaries (tropical and subtropical). Our findings showed that 70 biological samples from fish (92.11%) contained debris, with the tropical estuary exhibiting the highest abundance (n = 499 particles—67% of the total), dominated by laminar (film) particulate pollutants (76.75%). In this estuary, the gill exhibited the highest contamination index, with most particulate pollutants (<1 mm and 1–3 mm) found in 63.6% and 54.5% of samples, respectively. In the subtropical estuary, 246 debris particles (33% of the total) were detected in the biological samples, with 58.5% of particles being of the film type. The gastrointestinal tract had the highest contamination index in this region, with 70.6% of particles in the 1–3 mm size range. These results highlight the pervasive presence of particulate pollutants in estuarine ecosystems and the organ-specific contamination patterns in tropical and subtropical regions, underscoring the ecological risks posed by plastic waste to estuarine biodiversity in hotspot regions.