High latitude fish in a high CO2 world: Synergistic effects of elevated temperature and carbon dioxide on the metabolic rates of Antarctic notothenioids

Although the physiological response of teleost fishes to increased temperature has been well documented, there is only a small body of literature that examines the effects of ocean acidification on fish under ecologically relevant scenarios. Furthermore, little data exists which examines the possible synergistic effects of increased sea surface temperatures and pCO₂ levels, although it is well established that both will co-committedly change in the coming centuries. In this study we examined the effects of increased temperature, increased pCO₂, and a combination of these treatments on the resting metabolic rate (RMR) of four species of notothenioid fish, Trematomus bernacchii, T. hansoni, T. newnesi, and Pagothenia borchgrevinki, acclimated to treatment conditions for 7, 14 or 28 days. While most species appear capable of rapidly acclimating to increased pCO₂, temperature continues to impact RMRs for up to 28 days. One species in particular, T. newnesi, displayed no acclimatory response to any of the treatments regardless of acclimation time and may have a reduced capacity to respond to environmental change. Furthermore, we present evidence that temperature and pCO₂ act synergistically to further elevate the RMR and slow acclimation when compared to temperature or pCO₂ increases alone.