Microplastics in aquatic communities of neotropical agroecosystems

Microplastics (MP's) are pervasive pollutants; however, research on their ingestion by freshwater biota in the Neotropics remains limited, particularly in riverine ecosystems surrounded by agricultural landscapes. This study tested the hypothesis that MP's are present in streams within agricultural areas and that MP's loads in aquatic organisms can be predicted based on stream position and both taxonomic and ecological traits. Macroinvertebrates and fish were sampled at 18 sites across six streams, covering upper, middle, and lower reaches within the Comandaí basin (Brazil) during the winter and spring of 2022. Both macroinvertebrate and fish taxa with diverse ecological traits were selected within a broad range for MP's analysis. Fish body length and weight were measured to assess potential correlations with MP's loads. MP's were detected in organisms from all sampling sites. In total, 106 plastic particles were recovered from macroinvertebrates and 172 from fish. Most particles were blue/green polyethylene fibers. In fish, MP's presence was associated with specific trophic guilds, water column position, and taxa, whereas MP's loads in macroinvertebrates were consistent across taxa and trophic guilds. These findings highlight the vulnerability of freshwater organisms to plastic pollution throughout stream systems with certain fish groups exhibiting greater susceptibility to MP's ingestion.