Deep-water prawn Pandalus borealis displays a relatively high pH regulatory capacity in response to CO2-induced acidosis

Ocean acidification and possible leakage from subsea CO 2 storage may create unfavourable conditions for marine organisms. Deep-living animals are generally believed to be more vulnerable to elevated partial pressure of CO 2 (pCO 2 , environmental hypercapnia) than shallow-living species, but so far only a limited number of studies have investigated the effects of environmental hypercapnia on deep-living animals. In the present study, the deep-water prawn Pandalus borealis (Kryer, 1838) was subjected to time-dependent exposure to hypercapnic seawater (pCO 2 ~ 9100 atm; pH NBS 6.86) for up to 16 d. Surprisingly, animals were able to partially compensate extracellular acidosis under these severe conditions by accumulating buffering bicarbonate ions at levels comparable to those reported for shallow-living decapod crustaceans. pH regulation was achieved without significantly increasing the ion-regulating activity of total ATPase and Na + /K + -ATPase. Oxygen consumption rate was not substantially affected by exposure. A significant increase in ammonia ex cretion rate was found within the initial phase of exposure, possibly reflecting H + buffering by ammonia as a result of increased protein metabolism. The results from this study suggest that the deep-water prawn P. borealis has relatively well-developed mechanisms to counteract CO 2 -induced acidosis. This finding further indicates greater variation in CO 2 tolerance of deep-water organisms than previously assumed and greater tolerance in species with relatively high activity levels compared to less active species. More studies on species from different taxonomic groups and habitat depths are therefore needed to improve the knowledge on how deep-living organisms will respond to the challenges of a high CO 2 world.