• • Gastrointestinal tracts of wild fish in Baiyangdian Lake contained the highest microplastic load at 11.63 ± 10.76 items/individual, exceeding gill (7.44 ± 6.79) and muscle (3.91 ± 3.16) counts, indicating ingestion as the primary exposure route and posing a risk of trophic transfer.
• • Total microplastic abundance per fish ranged from 5 to 87 items, with a mean of 25.285 items; carnivorous and herbivorous species (e.g., snakehead and grass carp) exhibited significantly higher burdens than omnivorous and planktivorous species, demonstrating feeding habit as a key determinant of accumulation.
• • Over 90% of detected microplastics were fibers smaller than 1 mm, with dominant polymers being chlorinated polyethylene (CPE), polyethylene terephthalate (PET), polypropylene (PP), and polyethylene (PE), indicating sources from packaging and textile degradation.
• • When normalized to body weight, smaller fish (mosquitofish and topmouth gudgeon) had higher microplastic concentrations in the gastrointestinal tract than larger fish, suggesting that lighter organisms face greater per-gram exposure and may serve as sensitive indicators of microplastic pollution.