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Plastic microfibers in water, macroinvertebrates and Chilean pencil catfish across the Mapocho River basin (Chile): Occurrence, characteristics, exposure and trophic transfer trends

Plant Diversity 2026
Isidora Catalán-Muñoz, Brian G. Walker, Andrew White, Mauricio J. Cárter, Mariana Gajardo-Gamargo, Blanca E. Molina-Burgos, Gustavo Chiang

Summary

This field study documents the presence of plastic microfibers in water, aquatic macroinvertebrates, and Chilean silverside fish from freshwater ecosystems in Chile. Microfibers were detected across all sampled matrices, indicating widespread contamination and active transfer through the food web. The findings highlight plastic textile pollution as a significant threat to South American freshwater biodiversity.

Study Type Environmental

Microplastics (MPs) are omnipresent particles that can cause diverse perturbation in aquatic biota. In freshwater systems, their presence and accumulation in aquatic fauna depends on a combination of abiotic and biotic factors that are specific to each basin, with Wastewater Treatment Plant (WWTP) effluent being a significant source. In this study, we determined the abundance and characteristics of Microfibers (MFs) in water samples, as well as in different feeding guilds of benthic macroinvertebrates, and Chilean pencil catfish upstream and downstream of discharges from five WWTPs in Santiago. Additionally, an evaluation of bioaccumulation and/or trophic transfer trends of MFs in biotic matrices was conducted. The highest and lowest MF abundances in water samples were found at RS1 and RS2 locations, respectively (reference sites upstream any WWTPs). In macroinvertebrates, the highest and lowest MF intake was in RS1 and DS1, respectively. In catfish, the highest and lowest MF intake was in DS2 and DS3, respectively (both downstream sites). A certain relationship was evident: the larger catfish had a higher abundance of MFs, but only in the sites DS2 and DS3 located downstream of the WWTPs. However, this relationship was not statistically significant (p-value >0.05). Filter-feeders and collectors (scrapers and shredders) ingested the highest amounts of MFs at sites upstream and downstream of the WWTPs, respectively. A trophic transfer of MFs was evident when considering the total macroinvertebrate group and the pencil catfish. This process was enhanced at RS2, DS1, and DS2, but not at the three downstream sites. This study provides the first assessment of MPs in multiple environmental matrices for rivers in Chile. These findings highlight the necessity for continuous monitoring and long-term studies to understand the site-specific processes and factors that may influence the presence and movement of MPs within river systems, beyond the mere proximity of WWTPs.

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