Anurans as potential external vectors of putative anthropogenic microfibers in neotropical coastal wetlands

Anthropogenic microfibers are pervasive contaminants in aquatic ecosystems, yet their interactions with organisms are predominantly studied through ingestion. External adhesion represents a potentially important but overlooked pathway of anthropogenic microfiber transport. Here, we assessed the occurrence of putative anthropogenic microfibers adhering to the skin of adult anurans in coastal wetlands of southern Brazil, evaluating their potential role as external biological vectors. We sampled 165 individuals from nine species spanning aquatic, terrestrial, and arboreal ecological groups across four sites. Samples were processed using stereomicroscopy, and microfibers were identified based on morphological features and characterized by size and color. Differences in occurrence and load among ecological groups were evaluated using hurdle models. Microfibers were detected in 28.5% of individuals and occurred across seven species and all ecological groups. In total, 889 microfibers were recovered, with highly variable loads among individuals. Transparent microfibers overwhelmingly dominated samples (94.7%). The widespread presence of adhered microfibers among sampled individuals is consistent with microfiber exposure during the sampling period and with amphibian skin acting as a substrate for particle adhesion under the surveyed conditions. Although transport was not directly quantified, these findings highlight a previously underexplored pathway of organism–microfiber interaction, with potential implications for passive redistribution of contaminants across interconnected wetland ecosystems.