Microplastic Pollution in the Gastrointestinal Tract and Gills of Some Teleost and Sturgeon Fish from the Caspian Sea, Northern Iran

Abstract

The increasing microplastic (MP) pollution in the marine environment has raised global concern. The main risk of MPs in aquatic ecosystem is their bioaccumulation in aquatic organisms. While some studies reported MPs pollution in the digestive system of the Caspian Sea fish species, there is no research on sturgeon species, nor on fish gills. Here, we investigated the occurrence of MPs in the gastrointestinal tract (GIT) and gills of 62 specimens belonging to four species including three teleosts (Cyprinus carpio, Rutilus kutum and Chelon aurata) and one sturgeon (Acipenser persicus, a valuable endangered species) from the Caspian Sea between January and March 2022. Fish tissues were removed, exposed for 24 h to 10 % KOH and then dried on the filter papers. Particles were observed under stereomicroscope and analyzed by Raman micro‐spectrometry, SEM and EDS. A total of 91 MPs were detected in GIT (averaged 1.46 ± 1.17 items/individual) and 63 MPs in gills (averaged 1.01 ± 0.62 items/individual). There was not significant correlation between the number of MPs found in the both tissues and the fish body length, body weight, GIT weight and gill weight (P > 0.05), except between MPs isolated from gills and gill weight in C. carpio (rs = 0.707, P = 0.022). MPs abundance in the fish followed the order of A. persicus > C. aurata > R. kutum > C. carpio. MPs were found in the size range of 45−5000 µm and the particles with 300‒1000 µm in size were the most prevalent. MPs were common by fiber (74.68 %) in shape, red (30.53 %) in color and nylon (70.6 %) in polymer.