The microplastics pollution in bivalve Anodonta cygnea, water and sediments of the Siahdarvishan River (guilan)

Microplastic particles smaller than 5 mm are referred to as microplastics (MPs). Microplastic (MPs) pollution is considered a widespread global threat to aquatic ecosystems. The level of microplastic pollution in the bivalve Anodonta cygnea, water, and sediments of the Siyah darvishan River (Guilan) was studied. Various sources of pollutants, including microplastics enter the Siyah darvishan River. Samples of bivalves, sediments, and water were collected from 3 stations from June to September 2023. A total of 65 bivalve samples were collected and analyzed. The mean length and total weight of the collected bivalves were 113.90 ± 3.97 mm and 143.78 ± 14.96 grams, respectively. Microplastics were observed and identified in all samples. The average abundance of microplastics in bivalve tissue was 34.13 ± 11.88 particles per individual or 0.38 ± 0.15 particles per gram of soft tissue. The figure was, it was 853.33 ± 296.31 particles per kilogram of dry weight in sediment samples and 0.77 ± 0.15 particles per liter in water samples. There was no significant correlation in terms of the amount of microplastics and shape between water and bivalves, sediment and bivalves, and sediment and water (P< 0.05). However, a significant positive correlation was observed in terms of particle size between water and bivalves, sediment and bivalves, and sediment and water (P<0.05). Additionally, there was no correlation between microplastic concentration and the total weight, soft tissue weight or shell length (P< 0.05). The predominant shapes of microplastics were fibers and fragments, mainly black in color. The type of plastic polymer was identified using an FTIR-ATR device, with polypropylene (PP) and polyethylene (PE) being the most common polymers. The average size of particles in bivalve soft tissue and sediment across all stations was 0.5-1 mm and 1-2 mm in water.



Keywords: Bivalve Anodonta cygnea, Microplastic, Sediment, Polymere, River, Iran