Synergistic Effects of Ocean Acidification and Elevated Temperature Alter the Energy Landscape of an Extreme Stenotherm, Trematomus Bernacchii

Antarctic fishes of the suborder Notothenioidei have displayed incredibly narrow physiological limits in previous single stressor studies and may be particularly vulnerable to the impacts of global climate change. As such, this system provides a unique opportunity to examine the physiological trade-offs associated with acclimation to a warmer, more acidic ocean. Using both field and laboratory-based analyses, we have combined approaches from the fields of functional genomics and organismal physiology to examine how global climate change may impact energy utilization in Antarctic fishes. Our previous data has shown the emerald notothen, Trematomus bernacchii, displays a rapid acclimatory response with respect to resting metabolic rates following exposure to elevated temperature or pCO₂ and that these two stressors can act synergistically to extend the time necessary for acclimation. Here we highlight the molecular mechanisms underlying the physiological response of T. bernacchii after long-term acclimation to this multi-stressor scenario. RNAseq analysis of mRNA levels in gill and liver tissue were combined with cellular respiration measurements and biochemical analyses of key metabolic enzymes to highlight tissue specific changes in energy allocation associated with prominent cellular pathways. These integrated approaches have given us insight into the physiological costs of sub-lethal stress in these endemic fish.