Harpagifer bispinis, but not Patagonotothen tessellata, appears robust to interactive effects of ocean warming and acidification in southern Patagonia

Ocean warming and acidification challenge marine ectotherms with rapid, multiple and simultaneous environmental changes. As knowledge of these impacts on fish from the sub-Antarctic is scarce, this study seeks to explore the combined effects of warming and acidification on the thermal and metabolic responses of Patagonotothen tessellata and Harpagifer bispinis, two sympatric notothenioid fish from the Beagle Channel. Juveniles were exposed to present-day and near-future summer temperatures (~10 and 13 ◦C) and pCO2 levels (~500 and 1300 μatm) in a full factorial design. Their critical thermal minimum/maximum (CTmin/CTmax) were assessed and their partial thermal tolerance polygons were estimated. Oxygen consumption rates allowed us to calculate fish’ aerobic scope (AS) as the difference between the standard and maximum metabolic rates (SMR and MMR). The CTmin of both species were affected by temperature, pCO2 level and their interaction, while the CTmax of P. tessellata was affected by both factors and that of H. bispinis, only by temperature. The partial thermal tolerance polygon of P. tessellata significantly decreased with future pCO2 levels, while no changes were observed for H. bispinis. In P. tessellata, SMR and MMR were affected by temperature and pCO2 levels and the AS by their interaction. Conversely, H. bispinis showed no differences in SMR, MMR and AS under different conditions. The increase in SMR and decrease in AS of P. tessellata with future temperatures and pCO2 levels may explain the changes in its thermal tolerance, while for H. bispinis, either the species has a greater capacity to adapt its metabolic response to warming and acidification, or different physiological processes are responsible for the observed changes in its thermal tolerance. Overall, present information could be a valuable tool for forecasting shifts in habitat suitability across the distribution range of both species and other similar fish in the context of climate change.

Fil: Giménez, Eloísa Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina

Fil: Vanella, Fabián Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina

Fil: Wolinski, Laura Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego, Antártida e Islas del Atlántico Sur. Instituto de Ciencias Polares, Ambientales y Recursos Naturales; Argentina

Fil: Torres, Rodrigo. Centro de Investigacion En Ecosistemas de la Patagonia; . Centro de Investigación Dinámica de Ecosistemas Marinos de Altas Latitudes; Chile

Fil: Lattuca, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina