Behavioural, metabolic and neuroxidative effects in juvenile Sparus aurata exposed to conventional and biobased microplastics.

Microplastic pollution in marine environments has raised significant concerns. However, it remains unclear whether bioplastic particles are indeed more environmentally-friendly and less noxious to marine species than conventional petroleum-based plastics. This study aimed to adopt a holistic approach (integrating animal behaviour, plasma metabolite profiling, brain histopathology and biochemical markers indicative of neural function and antioxidant responses) to assess the ecotoxicological effects of juvenile gilthead seabream (Sparus aurata) orally exposed to petroleum-based (polyethylene terephthalate, PET), and bio- (polybutylene succinate, PBS and polypropylene 2,5-furandicarboxylate, PPF) microplastics, for a period of 28 days. The ability of fish to recover from stress induced by plastics exposure was also investigated, by analysing the aforementioned endpoints following a seven-day depuration period. Of the twelve plasmatic metabolites assessed, only two were significantly affected by microplastics ingestion - glucose levels increased in fish exposed to PET, while amylase activity decreased after exposure to all three microplastics. There was no evidence of severe and/or irreversible alterations in neuronal function (i.e. acetylcholinesterase activity), cortisol levels, behaviour or brain histopathological structure. The antioxidant defence system was mildly affected by the exposure to PET and PBS (i.e. decreased catalase activity), although this effect was no longer observed during the depuration period. At the end of the exposure period no cell lipid peroxidation occurred, however, PPF stimulated the ubiquitin-proteasome pathway (i.e. increased ubiquitin content). Overall, the exposure to these microplastics could not be conclusively or clearly linked to persistent toxicity in gilthead seabream.