Evaluation of microplastic presence and risks in freshwater fish from Anzali International Wetland, Iran

Microplastics (MPs) are an emerging class of pollutants with growing evidence of their accumulation in aquatic organisms. This study assessed the presence, characteristics, and ecological risks of MPs in the gills and gastrointestinal tracts (GITs) of five fish species from Anzali Wetland, Iran: Prussian carp (Carassius gibelio), perch (Perca fluviatilis), tench (Tinca tinca), common carp (Cyprinus carpio), and northern pike (Esox lucius). The average MPs abundance was 5.50 ± 3.36 particles per individual, with Tinca tinca showing the highest contamination (8.16 ± 4.45 MPs) and Perca fluviatilis the lowest (2.60 ± 1.26 MPs). Omnivorous and benthic species exhibited significantly higher MPs loads compared to carnivorous and pelagic species. Most MPs were blue (38%), fiber-shaped (78%), and sized between 250 and 500 µm (26%), with polyethylene, polypropylene, and polyamide identified as the dominant polymer types. Ecological risk assessment indicated a high potential threat to the wetland’s biodiversity. These findings demonstrate that MPs are bioaccumulating in key fish species of Anzali Wetland, with implications for food webs and human health. The study underscores the urgent need for stricter pollution control, enhanced public awareness, and improved methodologies for detecting smaller MPs and nanoplastics to effectively monitor and mitigate this growing environmental threat.