Impact of polypropylene microplastics and chemical pollutants on European sea bass (Dicentrarchus labrax) gut microbiota and health

Plastic pollution has become a global problem for marine ecosystems. Microplastics (MPs) are consumed by several
marine organisms, including benthic and pelagic fish species that confuse themwith food sources, thus contributing
to bioaccumulation along the food chain. In addition to structural intestinal damage, ingestion of MPs
represents a pathway for fish exposure to potentially hazardous chemicals, too. Most of them are endocrine disrupters,
genotoxic or induce immune depression in fish.
Accordingly, we assessed the combined toxicological effects of microplastics (MPs) and adsorbed pollutants by
adding them to marine fish diet. European sea bass (Dicentrarchus labrax) juveniles were fed for 60 days with
feeds containing polypropylene MPs, either virgin or contaminated with chemical pollutants (a blend of
dichlorodiphenyldichloroethylene, chlorpyrifos, and benzophenone-3). The data demonstrated a synergic action
of MPs and chemical pollutants to induce an inflammatory-like response in distal intestine of sea bass as shown
by the up regulation of cytokine il-6 and tnf-α expression.Morphological analysis detected the presence of a focus
of lymphocytes in anterior and posterior intestinal segments of fish fed with contaminants in the diet. With regard
to microbiota, significant changes in bacterial species richness, beta diversity, and composition of gut microbiota
were observed as a consequence of both pollutants and pollutedMPs ingestion. These perturbations in gut
microbial communities, including the reduction of beneficial lactic acid bacteria and the increase in potential
pathogenic microorganism (Proteobacteria and Vibrionales), were undeniable signs of intestinal dysbiosis,