Trophic niche features influence microplastic ingestion in Mediterranean fish species

Widespread microplastic (MP) contamination in the marine environment has raised global concern in the last decade. Scientific evidence of the adverse effects of MP on organisms is growing fast and there is urgent need to fulfil the knowledge gaps about the trophic drivers that lead to such contamination processes and resulting impacts. Fish are considered good bioindicators of MP contamination due to their easy availability, high ecological and commercial value, however our understanding of how trophic niche influences MP ingestion is limited. Here, we investigated the occurrence and abundance of MP in the gastrointestinal tract of 8 commercial fish species (Boops boops, Engraulis encrasicolus, Merluccius merluccius, Micromesistius poutassou, Mullus barbatus, Sardina pilchardus, Scomber scombrus and Trachurus trachurus) from North-western Mediterranean Sea, with the aim to assess the relationship with fish trophic niche features (trophic position, isotopic niche width and diversity), trophic habit (zooplanktivorous, benthivorous and piscivorous), habitat (demersal, pelagic and benthopelagic) and body condition. 25% of the 396 fish analysed presented MP particles. Trophic niche features, evaluated through stable carbon and nitrogen isotope analysis, revealed to influence the occurrence of MP ingested, while fish trophic habit and habitat seemed to influence the abundance of ingested MP. Fish species displaying wider isotopic niche and higher trophic diversity resulted to be more likely to incur in MP ingestion in each habitat. Also, MPs were more abundant in zooplanktivores, benthopelagic and pelagic species than in demersal species and in individuals with lower body condition. These results suggest that the more the diet of a species is differentiated, the higher is the risk of plastic ingestion, which is also linked to the individual body condition. Overall, this study highlights the importance of considering trophic niche features as a promising approach to study the drivers of MP contamination.