Metabolic responses to high CO conditions at a CO vent site in juveniles of a marine isopod species assemblage.

We are starting to understand the relationship between metabolic rate responses and species' ability to respond to exposure to high CO. However, most of our knowledge has come from investigations of single species. The examination of metabolic responses of closely related species with differing distributions around natural elevated CO areas may be useful to inform our understanding of their adaptive significance. Furthermore, little is known about the physiological responses of marine invertebrate juveniles to high CO, despite the fact they are known to be sensitive to other stressors, often acting as bottlenecks for future species success. We conducted an in situ transplant experiment using juveniles of isopods found living inside and around a high CO vent (Ischia, Italy): the CO 'tolerant' and 'sensitive' and . This allowed us to test for any generality of the hypothesis that CO sensitive marine invertebrates may be those that experience trade-offs between energy metabolism and cellular homoeostasis under high CO conditions. Both sensitive species were able to maintain their energy metabolism under high CO conditions, but in this may occur at the expense of [carbonic anhydrase], confirming our hypothesis. By comparison, the tolerant appeared metabolically well adapted to high CO, being able to upregulate ATP production without recourse to anaerobiosis. These isopods are important keystone species; however, given they differ in their metabolic responses to future CO, shifts in the structure of the marine ecosystems they inhabit may be expected under future ocean acidification conditions.