Environmental pollution from plastic debris is a major global concern, being a potential threat to marine organisms and ecosystems. The accumulation of microplastics (MPs) in the oceans has notable ecological implications due to their long persistence, their potential ecotoxicity, and their ability to adsorb other pollutants and act as vectors of pathogens. Nevertheless, whereas the number of investigations documenting the presence of MPs in wild fish has increased, less studies have addressed the toxicological effects associated with the ingestion of MPs in long-term laboratory conditions. The aim of the present study was to assess the physiological response of gilthead seabream (Sparus aurata) exposed to low-density polyethylene (LDPE) MPs during a 90-day exposure followed by an extra 30 days of depuration through the application of oxidative stress biomarkers in the gut. No changes were observed in the Fulton condition factor of fish associated with MP intake. The activities of antioxidant enzymes and glutathione s-transferase and the levels of reduced glutathione progressively increased throughout the study in the MPs-fed group compared to the control group, reaching the highest values at 90 days. Similarly, the activity of the pro-inflammatory enzyme, myeloperoxidase, and the levels of oxidative damage markers -malondialdehyde and protein carbonyls-also increased after 90 days of exposure to an enriched diet with MPs. During the 30-day depuration period, all the biomarkers analysed tended to normalize, with the majority recovering values similar to those of the control group. In conclusion, MPs exposure during 90 days to S. aurata induced oxidative stress and a pro-inflammatory response in gut, and were able to recover after the exposure to MPs was removed.

During the last years, ingestion of microplastics (MPs) has been quantified in marine species both with an ecological and commercial interest at sea and under experimental conditions, highlighting the importance to assess MP ingestion in commercially and aquaculture important species such as gilthead seabream (Sparus aurata) fish. In order to study the ingestion of MPs in a commercially valuable species, gilthead seabreams were exposed to an enriched diet with virgin and weathered low-density polyethylene (LDPE) pellets for three months followed by a detoxification period of one month of no exposure to MP enriched diets. Our results indicate that MP ingestion in these fishes increased with exposure time, and differences were found between treatments, showing the highest ingestion values after three months of exposure to MP enriched diets and in the weathered treatment. However, after one month of detoxification, no MPs were found in the gastrointestinal tracts of fish, reflecting no long-term retention of MPs in Sparus aurata digestive system. According to results from this study, exposure of fish to MP enriched diets does not affect fish size neither the Fulton’s condition index as both parameters increased with time in all treatments (control, virgin and weathered). Both carbon and nitrogen isotopic signatures decreased with fish size in all treatments which could be related to an increase of nitrogen deposition efficiency in fish muscle with a high protein assimilation during the first months of Sparus aurata.

Microplastic pollution and its potential impacts on humans become a global concern. This study is the first study examining the microplastic ingestion in the commercially important species Oncorhynchus mykiss Rainbow trout (Walbaum, 1792), Sparus aurata Gilthead seabream Linnaeus, 1758, and Dicentrarchus labrax European seabass (Linnaeus, 1758) from Turkey. The occurrence frequency of microplastic (MP)in the gastrointestinal tract (GIT) was varied between 50 and 63 %. The highest MP abundance in the GIT was estimated in Rainbow trout (1.2 MPs individual⁻¹) followed by European seabass (0.95 MPs individual⁻¹) and Gilthead seabream (0.8 MPs individual⁻¹). Most of the extracted microplastic particles were black (61 %) and blue (27 %) in color and fiber (80 %) in shape. Major identified polymers were polyethylene (25 %), polyester (20 %), polyamide (10 %). Since fish consumption is an important route for MPs, results light up the danger potential for humans. This study will fill the information gap in Turkey and show the necessity of protection measures in aquaculture industry.

In vitro methods have gained rising importance in ecotoxicology due to ethical concerns. The aim of this study was to assess the single and combined in vitro effects of gold, as nanoparticle (AuNPs) and ionic (Au⁺) form, and the pharmaceutical gemfibrozil (GEM). Sparus aurata liver organ culture was exposed to gold (4 to 7200 μg·L⁻¹), GEM (1.5 to 15,000 μg·L⁻¹) and combination 80 μg·L⁻¹ gold +150 μg·L⁻¹ GEM for 24 h. Endpoints related with antioxidant status, peroxidative/genetic damage were assessed. AuNPs caused more effects than Au⁺, increasing catalase and glutathione reductase activities and damaging DNA and cellular membranes. Effects were dependent on AuNPs size, coating and concentration. GEM damaged DNA at an environmentally relevant concentration, 1.5 μg·L⁻¹. Overall, the effects of the combined exposures were higher than the predicted, based on single exposures. This study showed that liver culture can be a useful model to study contaminants effects.