Impact of a chronic waterborne exposure to polystyrene nanoplastics on the gilthead seabream (Sparus aurata): Combining traditional and multi-omics approaches

Recirculated aquaculture systems (RAS) represent valuable assets for meeting the growing seafood demand in a sustainable way. However, nanoplastic (NP <1000 nm, respectively) contamination still poses a risk in such systems. This study aimed to elucidate the effect of prolonged waterborne exposures to polystyrene nanoplastics (PSNPs) on one of the most commercially important fish species of Mediterranean aquaculture, the gilthead seabream (Sparus aurata). Juvenile fish were exposed to an environmentally relevant and a spiked concentration of PSNPs (100 µg/L and 1000 µg/L, respectively) over 28 days, and a series of traditional (i.e. morphometrics, haematology, histology) and omics (i.e. metabolomics, microbiome sequencing) approaches were employed to obtain a comprehensive understanding of the toxicity of PSNPs in S. aurata. The present results indicate that the studied experimental conditions did not impact morphometrics or haematological profile, nor did it cause histopathological lesions. However, waterborne PSNPs induced changes in the microbiome, significantly decreasing the Shannon's diversity index in fish exposed to high concentrations of PSNPs and altering the relative abundance of microbiota at the family level. Moreover, the metabolomic profile in the plasma of exposed S. aurata was altered in a dose-specific manner, with glutamate, proline, glycerol and formate levels being significantly up-regulated under spiked concentrations of PSNPs, and valine being significantly lower in individuals exposed to environmentally relevant concentrations. Overall, the results suggest that PSNPs might have potential repercussions particularly on the energy metabolism and overall performance of fish in the long term, affecting the production of the aquaculture industry.