Aquaculture Sciences

Aquaculture Sciences

Characterization and source apportionment of microplastics in four fish species from the Sefid-Rud River estuary, Iran

Document Type : Original Article

Authors
Pouya Pourahmadi
Mina Torabifard
Shahrzad Khoramnejadian
Behnaz Moradi Ghiasabadi
Department of Environment, Dmv.c., Islamic Azad University, Damavand, Iran.
Abstract
Microplastic pollution is an emerging and widespread threat to aquatic ecosystems worldwide. The Sefidrud estuary is one of the major entry points of freshwater and contaminants into the southern Caspian Sea. This study aimed to investigate the abundance, distribution, and physicochemical characteristics of microplastics in the gastrointestinal tract of four fish species with different ecological niches (Alburnus chalcoides, Neogobius melanostomus, Rutilus frisii, and Chelon saliens) during autumn 2024. The gastrointestinal tracts were chemically digested using KOH, and the extracted microplastic particles were isolated, counted, and classified based on their physical properties. The polymer composition of a subset of particles was identified using FTIR spectroscopy. The results revealed that all species were contaminated with micro plastics, with the highest abundance observed in N. melanostomus (3.21±0.6 particles per individual). Fibers were the dominant shape in most species; however, the benthic species N. melanostomus and C. saliens exhibited a greater diversity of fragments and films. A distinct variation in polymer composition was observed among species. Polyethylene (PE) was detected exclusively in A. chalcoides, polyethylene terephthalate (PET) solely in R. frisii, and polyamide (PA) only in N. melanostomus. These findings indicate that ecological niche and feeding strategy are key determinants of micro plastic exposure pathways, resulting in species-specific contamination profiles. Fish in this ecosystem can serve as effective bioindicators for tracing diverse pollution sources. The study highlights the urgent need for targeted management actions to reduce plastic inputs into this vital ecosystem.
Keywords
Fibers
Native Fish
Microplastic pollution
Polymer composition
Sefid-Rud River
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Aquaculture Sciences
Volume 13, Issue 2
October 2025
Pages 50-61