Adult Antarctic krill proves resilient in a simulated high CO 2 ocean

Antarctic krill ( Euphausia superba ) have a keystone role in the Southern Ocean, as the primary prey of Antarctic predators. Decreases in krill abundance could result in a major ecological regime shift, but there is limited information on how climate change may affect krill. Increasing anthropogenic carbon dioxide (CO 2 ) emissions are causing ocean acidification, as absorption of atmospheric CO 2 in seawater alters ocean chemistry. Ocean acidification increases mortality and negatively affects physiological functioning in some marine invertebrates, and is predicted to occur most rapidly at high latitudes. Here we show that, in the laboratory, adult krill are able to survive, grow, store fat, mature, and maintain respiration rates when exposed to near-future ocean acidification (1000–2000 μatm p CO 2 ) for one year. Despite differences in seawater p CO 2 incubation conditions, adult krill are able to actively maintain the acid-base balance of their body fluids in near-future p CO 2 , which enhances their resilience to ocean acidification.