Microplastic occurrence in selected aquatic species of the Persian Gulf: No evidence of trophic transfer or effect of diet

Microplastic (MP) contamination in the aquatic ecosystems is a growing global environmental issue that can cause detrimental effects on aquatic species. In this study, MPs in fish (six species, 195 specimens), molluscs (one species, 21 specimens), and crustaceans (three species, 264 specimens) with various biometry, trophic levels, feeding habits, and habitat characteristics were investigated in three habitats: a river, an estuary, and a harbor in the Persian Gulf. Gastrointestinal tracts, gills and skin of targeted samples were chemically digested and the MPs recovered were counted and analyzed with optical microscopy, Raman spectroscopy and SEM/EDX. MPs counted in species of the Bushehr Port (11.4 ± 4.4 MPs/10 g) were significantly higher than in the other locations. The total abundance of MPs ranged from 4.0 ± 2.3 MPs/10 g for Metapenaeus affinis to 28.0 ± 6.4 MPs/10 g for Sepia pharaonis. Importantly, no significant relationships were found between the number of MPs in different inedible tissues, trophic levels, and types of feeding habit. Nevertheless, MPs were more abundant (p < 0.05) in benthos (34.7 MPs/10 g) than benthopelagic (25.9 MPs/10 g) and pelagic species (22.6 MPs/10 g). A total of 96.6 % of the identified MPs were fibers, these were generally ≥1000 μm and were mainly black/grey. Fibers may come from municipal wastewater effluents and fishing activities. The findings of this study present new insights into MP contamination routes in aquatic species.