Increased seawater temperatures cause temporal shifts in catabolic pathways of Antarctic krill Euphausia superba

Antarctic krill (Euphausia superba) hold a central position in the Southern Ocean food web, yet little is known about how they might respond to anthropogenic climate change, in particular the projected rise in temperature in their habitat. Krill‘s life cycle and metabolism are successfully adapted and timed closely to their highly seasonal environment. An elevation in sea water temperature has the potential to disrupt this delicate interplay, desynchronizing krill physiology with essential cornerstones in the course of the year. The aim of this study was to elucidate the direct effects of rising sea water temperatures on Antarctic krill metabolism. To this end, krill were exposed to gradually increasing temperatures from 0.5°C to 7°C over a period of four months. Over the course of the experiment, respiration and morphometric parameters including growth and maturation were regularly monitored. These observations supplement the analysis of key enzyme activities in a range of metabolic pathways including glycolysis (pyruvate kinase), beta-oxidation (3-hydroxyacyl-CoA-dehydrogenase), Krebs cycle (malate dehydrogenase, citrate synthase) and cellular respiration (cytochrome C oxidase). In combination with the analysis of elemental composition these data add to our understanding of the response mechanisms of krill to a changing environment. The results are discussed in view of possible implications in the context of climate change, such as ecological mis-matches with Antarctic seasonality