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Microplastic Ingestion in Three Deep-Sea Fish Species: First Ecological Insights from Stable Isotope Analysis

Microplastics 2026
Eleonora Monfardini, Maria Letizia Costantini, Tommaso Valente, Laura Ciaralli, Giulio Careddu, Giovanna Jona Lasinio, Daniela Berto, Federico Rampazzo, Greta Panunzi, M. Severini, Martina Radicioli, Cecilia Silvestri, Marco Matiddi

Summary

Scientists found microplastics in over a third of deep-sea fish sampled from the Mediterranean Sea, confirming that plastic pollution has reached even fish living far from the surface and human activity. Interestingly, what a fish ate didn't affect how much plastic it swallowed, but it did influence the size and variety of plastic particles found in its gut—meaning different fish species may carry different types of plastic contamination. Since some of these deep-sea fish end up in the human food supply, this research helps scientists better understand how plastic moves through ocean food webs and eventually onto our plates.

Microplastic (MP) pollution is an emerging environmental stressor in marine ecosystems, yet its relationship with trophic ecology remains poorly understood in deep-sea environments. This study investigated MP ingestion in relation to trophic ecology in three deep-sea fish species (Chlorophthalmus agassizi, Hoplostethus mediterraneus, and Coelorinchus caelorhincus) from the central Tyrrhenian Sea (Western Mediterranean). Stable isotope analysis (δ13C and δ15N) was combined with detailed characterisation of ingested MPs to assess trophic niches, trophic position, and species-specific ingestion patterns. The three species showed distinct isotopic signatures, with C. agassizi occupying a lower trophic position, while H. mediterraneus and C. caelorhincus overlapped at higher trophic levels. MPs were detected in all species, with an overall frequency of occurrence of 34.4%, and no significant interspecific differences in occurrence or abundance were observed. However, significant differences emerged in MP characteristics. C. caelorhincus, which exhibited the widest isotopic niche, ingested larger and more diverse particles, whereas C. agassizi showed lower occurrence but higher particle loads in affected individuals. These results suggest that trophic ecology is not clearly associated with MP ingestion rates but may influence the size and diversity of ingested particles, highlighting ecological drivers of exposure in deep-sea ecosystems.

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