Pollution status of microplastics in freshwater basins of Türkiye: evidence from all Barbus (Daudin, 1805) species

Abstract

Microplastic (MP) pollution in freshwater ecosystems is a growing global concern, yet long-term data tracking its historical progression remains scarce. This study provides a retrospective analysis of MP ingestion in 12 Barbus species collected from five major hydrological basins in Türkiye between 2004 and 2018. A total of 373 collection specimens were examined to quantify MP abundance, characterize polymer types using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and evaluate spatio-temporal patterns. Microplastics were detected in 19.8% of the individuals, with an average abundance of 0.27 MP/individual. The Caspian Sea basin exhibited the highest observed MP concentrations (1.67 MP/individual), though no statistically significant differences were determined among basins. Fibers were the dominant morphology, and ethylene–vinyl acetate and polyamide were the most frequent polymer types. Notably, MP ingestion was persistent throughout the study period, indicating a chronic presence of plastic in Turkish freshwater systems rather than a significant temporal trend. The results suggest that benthic Barbus species serve as suitable indicators for monitoring sediment-associated MP pollution, although their capacity to differentiate localized pollution gradients requires further investigation. This study underscores the role of museum collections in bridging historical data gaps and provides a baseline for future freshwater management strategies.