Molecular and biochemical responsiveness toward climate change in the Antarctic fish Trematomus bernacchii

Antarctic marine ecosystems are very sensitive to climate change, and organisms adapted to such extreme environmental conditions might be seriously affected by glogal warming and ocean acidification. These effects can be further exacerbated by the presence of specific local features, like the naturally high bioavailability of cadmium in upwelling areas. In this study, the Antarctic rock cod Trematomus bernacchii was chosen as a key sentinel species, and exposed for 2 weeks to cadmium (40 µg/L) and various combinations of pH (8.2 and 7.4) and temperature (-1 and +1 °C). besides Cd accumulation, a wide panel of early warning biomarkers was analysed at molecular and catalytic level in liver and gills; these parameters included metallothioneins, the antioxidant regulation system Nrf2-Keap1, individual antioxidants like catalase, glutathione peroxidase and superoxide dismutase. the results indicated reciprocal interactions between multiple stressors, and a different sensitivity of tissues both at molecular and at catalytic level. Despite cadmium bioaccumulation, limited variations occurred for metallothioneins. A certain sensitivity to prooxidant challenge was highlighted by molecular variations of the Nrf2-Keap1 pathway in both tissues. Cellular adaptation to high basal content of cadmium and to environmental oxidative conditions were considered as responsible for the generally limited effects caused by additional stressors. Nonetheless, a certain modulation of antioxidants in all treated groups reflected an unbalance in oxyradical metabolism and an increase of lipid peroxidation and DNA damage.