Microplastics (MPs) are emerging contaminants in freshwater ecosystems; however, field-based evidence linking the ingestion of MPs to biological conditions in wild fish remains limited. This study examined the occurrence of MPs, polymer composition, and associated biological parameters in wild populations of common bleak ( Alburnus alburnus ) from two sites along the Serbian stretch of the Danube River. The gastrointestinal tracts of 61 individuals were analyzed using visual inspection, chemical digestion, and ATR-FTIR spectroscopy, and results were integrated with biological parameters. Microplastics were detected in 51% of specimens, with 1 to 3 particles per individual. Four polymer types were identified (polyethylene, polypropylene, ethylene–vinyl acetate, and polyamide). Generalized linear models showed that MPs abundance differed between sites, while MPs occurrence was primarily associated with biological parameters. Longer individuals had a higher probability of MPs presence, whereas lower body weight relative to length and reduced Fulton’s condition factor were consistently associated with MPs occurrence. Although the average MPs load (~ 0.5 particles per fish) was well below laboratory toxicity thresholds, observed associations indicate ecological relevance under natural exposure conditions. Due to its pelagic feeding behavior and rapid response to suspended particles, A. alburnus represents a sensitive bioindicator for monitoring MPs contamination in large river systems.
Nikolić et al. (2026) studied this question.