RESUMEN
Microplastic is releaseing to the aquatic environment worldwide, so they considered as a global issue and appeare to be widespread in all level of aquatic ecosystems and reveal serious threats to biota. Since they are often ingested by living organisms, the major concern is their transferring from lower trophic level to higher trophic level through the food chain. Due to the importance of Gorgan Bay as one of the ecologically important areas of the Caspian Sea and the need for fundamental information on the pollution status of this region, a study conducted for evaluation of microplastic pollution in sediments, fish and benthose, from 3 areas (north, central, south) through sampling from 21 stations. The range of microplastics (MPs) abundance in sediments was 80 ± 25 to 740 ± 105 n/kg. Fibers, Black MPs, and size of 1-2 mm (42.4%) were prevalence observed in sediment and living organisms. According to the FTIR results, among studied organisms, the most microplastic levels were found in the soft tissues of fish Neogobius melanostomus (39 MP/g) and mussel Cerastoderma lamarcki (19.8 MP/g) dry weight. The results of this study present the comprehensive information on MPs distribution and charecteristics in sediments, fish and mussel of Gorgan Bay which could help to run better management over this sensitive ecosystem and would be a start point for further research on MPs effect on organisms of the Caspian sea.