Microplastic Pollution in the Gastrointestinal Tract of Two Fish Species from the Zarrineh River, Southern Basin of Lake Urmia, Iran

As the newest contaminants, the microplastics cause environmental issues and may lead to several threats for living organisms and human beings. In Iran, riverine fishes are considered a good food resource; therefore, the necessity of studying these pollutants should be emphasized. This study is the first work reporting the occurrence of microplastics in the gastrointestinal tract of two fish species in the Zarrineh River. A total of ۸۶ fish specimens were collected from four stations depending on their distance to dams. After dissection, GI tracts of fish were excised. Afterwards, microplastics extraction was done based on the protocol of alkaline digestion, density separation through Nal, and Fourier-transform infrared (FTIR) spectroscopy. According to the results, ۶۷۹ microplastic particles were isolated from fish specimens. Also, microplastics were found in ۱۰۰% of samples. The mean number of microplastics was the highest for B. lacerta species in station S۲ (۱۳.۲±۱.۴۵ particles/individual). Fiber-shaped microplastics comprised ۶۰-۸۰% of total microplastics. In addition, microplastics less than ۱۰۰ μm were more abundant compared to larger particles. Black and blue colors were the most common colors. Finally, according to FTIR analysis, the main detected polymers included polyethylene (PE), polypropylene (PP), polystyrene (PS), and nylon (PA). It could be concluded that microplastic pollution poses significant health risks to both fish and people living around the Zarrineh River. Therefore, because of its critical role in the supply of drinking water for Tabriz metropolis and feeding the Lake Urmia, immediate management should be taken into account.

Keywords:

Microplastic , Fish , Zarrineh River , Lake Urmia , Gastrointestinal tract