Abstract
Ocean-warming and acidification jeopardize Antarctic marine species, adapted to cold and constant conditions and naturally exposed to high pro-oxidant pressures and cadmium (Cd) bioavailability. The aim of this study was to investigate if projected temperature increase and pH reduction may affect the accumulation and the effects of Cd in the rockcod Trematomus bernacchii. Organisms were exposed for 14 days to six scenarios, combining environmental or increased temperature (−1 °C, +1 °C) and control or reduced pH (8.05, 7.60), either with or without Cd (40 µg/L). Responses in liver and gills were analyzed at different levels, including mRNA and functional measurements of metallothioneins and of a wide battery of antioxidants, integrated with the evaluation of the total antioxidant capacity and onset of oxidative damages. In the gills, metallothioneins and mRNA of antioxidant genes (nrf2, keap1, cat, gpx1) increased after Cd exposure, but such effects were softened by warming and acidification. Antioxidants showed slighter variations at the enzymatic level, while Cd caused glutathione increase under warming and acidified scenarios. In the liver, due to higher basal antioxidant protection, limited effects were observed. Genotoxic damage increased under the combined stressors scenario. Overall results highlighted the modulation of the oxidative stress response to Cd by multiple stressors, suggesting the vulnerability of T. bernacchii under predicted ocean change scenarios.
Highlights
The massive anthropogenic emissions of greenhouse gases are affecting global ocean characteristics: the Southern Ocean has a major role in absorbing excess heat and CO2 released in the atmosphere [1,2]
Metallothioneins revealed a significant reduction of mRNA in gills of organisms exposed to temperature increase, while protein levels slightly increased in gills of Cd-exposed
No significant difference compared to control organisms was measured in livers of exposed organisms, neither for mRNA nor for proteins (Figure 1D,F)
Summary
Published: 9 March 2021The massive anthropogenic emissions of greenhouse gases are affecting global ocean characteristics: the Southern Ocean has a major role in absorbing excess heat and CO2 released in the atmosphere [1,2]. The current trend is expected to increase the temperature in the upper Southern Ocean by 1–3 ◦ C by the end of the century [2], and to further exacerbate the challenge of ocean acidification. Studies on Antarctic calcifying organisms depicted several biological effects of increased temperature and pCO2 , which include altered development, morphological changes, shell dissolution, reproductive alterations and oxidative unbalance [3,4,5,6,7]. Single and interactive effects of temperature and pH/pCO2 stress have been addressed in polar fishes, with developmental delays, altered acclimation capacity, metabolic shifts and oxidative unbalance [8,9,10,11,12,13,14]. The emerald rockcod Trematomus bernacchii is widely used as a bioindicator organism of Antarctic
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