Impact of sublethal contaminants mixtures on the immune system of Sparus aurata: Implications for marine ecosystem health

Abstract

The presence of various contaminants in aquatic environments has raised concerns regarding the potential consequences of mixtures of different agents from diverse origins, including heavy metals, polyfluorinated compounds, polychlorinated biphenyls, polybrominated diphenyl ether, as well as a wide range of pharmaceutical compounds and their byproducts. To assess the relationship between these compounds and their impact on marine organisms, varying concentrations of a blend comprising 2,2′,4,4′-tetrabromodiphenyl ether 47 (BDE-47), carbamazepine (CBZ), and cadmium chloride (CdCl₂) were introduced into the diet of gilthead seabream (Sparus aurata), a marine organism used as a model. Forty specimens were placed into six aquaria and fed with commercial diet containing either a vehicle (control) or a mixture of two sub-lethal doses of BDE-47, CBZ and CdCl₂ (D1 or D2). The animals were fed for 15 days and subsequently maintained for another 15 days on a control diet for a detoxification period. Liver and intestine samples were obtained at 15 and 30 days of the trial. Different parameters related to the immune system, detoxification and antioxidant defences were analysed. The findings indicate that the combined exposure to sub-lethal amounts of CBZ, CdCl₂, and BDE-47 through dietary supplementation has a significant effect on the liver and intestine structures, in addition to causing dysregulation of antioxidant and cell cycle factors. Despite the sub-lethal nature of the doses, it has been demonstrated that the interaction between this mixture of compounds and the primary detoxification organ, as well as the digestive system, indicates a prolonged impact on the organisms. Extended exposure to a mixture of various toxic substances may lead to substantial changes in the immunity of marine organisms and their overall well-being, potentially affecting marine biota in the long term.