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Linking stable isotopes and microplastic exposure in pelagic fish from the Sea of Oman: Habitat use and ecological niche effects
Summary
Scientists found microplastics—mostly tiny blue fibers—in the guts of three popular fish species from the Sea of Oman, with over half of all fish tested containing plastic bits. Interestingly, where and how a fish lives and feeds mattered more for plastic exposure than its position in the food chain, meaning even fish we might assume are "cleaner" eaters could still be swallowing plastic. Since these fish are commonly eaten by people, this research helps identify which environmental factors put seafood at higher risk for microplastic contamination, information that matters for anyone who eats fish regularly.
Microplastic (MP) contamination and its transfer within marine food webs are major environmental issues, especially for commercially important fish species. This study integrated stable isotope measurements (δC, δN) with microplastic assessment in the gastrointestinal tracts of three pelagic fish species-Selar crumenophthalmus, Rastrelliger kanagurta, and Thunnus tonggol-from the Sea of Oman, where such comprehensive studies are limited. Stable isotope analysis revealed no significant differences in δN among species, indicating similar relative trophic positions, while significant variation in δC suggested differences in carbon-source utilization and habitat use. Microplastics (<5 mm) were detected in all species, with occurrence rates ranging from 53.3% to 76.7%, and were mostly composed of small fibers, particularly blue fibers. No clear relationship was observed between microplastic abundance or particle size and relative trophic position within the limited trophic range represented by the studied assemblage. Instead, microplastic ingestion patterns appeared to be primarily influenced by environmental exposure and species-specific ecological traits, including feeding behavior and habitat use. Differences in carbon source utilization and isotopic niche characteristics suggest that ecological niche and habitat-related factors may play a more important role in shaping microplastic exposure than trophic position alone. Overall, these findings highlight the importance of integrating trophic ecology with environmental drivers to better understand microplastic distribution in marine ecosystems. This study provides baseline information for the Sea of Oman and contributes to a broader understanding of the ecological processes influencing microplastic exposure in pelagic food webs.