Bioaccumulation and stress markers in fish from an impacted area: Effects of mercury in the marine food system

Abstract

In this study, wild benthic and demersal fish species (Diplodus annularis, Pagellus erythrinus and Mullus barbatus) from the highly contaminated area of Augusta Bay and from control near sites (Marzamemi and Capo Passero) were selected, to investigate Hg bioaccumulation and its effects on stress, welfare, metabolism and quality. Specifically, biomarkers involved in stress response, oxidative adaptation (Nrf2, Hif-1α and Hsp70), cell cycle regulation (p53 and mTOR), central metabolism (Fas and Glut-4) and inflammatory responses (nuclear factor-κB (NF-κB)) were analyzed. Total lipid content, fatty acid profile and malondialdehyde (MDA) levels were also investigated in muscle and liver tissue to assess oxidative stress and its impact on molecular responses. Hg levels were significantly higher in fish from the impacted area compared to control group as were the levels of biomolecular markers related to different stress responses. In particular, the changes in the levels of proteins involved in the antioxidant defence system, cell cycle progression and lipid composition, suggest the induction of oxidative stress in the liver. Indeed, lipid content and polyunsaturated fatty acids (PUFAs), resulted significantly reduced in fish from the impact with respect to the control sites (p < 0.05), while MDA, biomarkers of lipid peroxidation, resulted increased in lots from impact sites (p < 0.05), in correspondence to the highest level of Hg in their tissues. Overall, this study highlights that bioaccumulation levels in marine organisms, integrated with biochemical and molecular biomarkers related to health, metabolism and quality, could be a valuable tool for environmental assessment and monitoring and for the management of highly polluted marine areas.