The present study aimed to contribute to the knowledge on the intraspecific variations of enzyme activities in populations of Calanus finmarchicus from different longitudes across the North Atlantic Ocean and their relation to changing environmental conditions. C. finmarchicus was sampled across the North Atlantic in basins with decreasing temperature regimes from east to west (Iceland Basin, Irminger Basin and Labrador Basin) in late March/early April 2013. Potential maximum enzyme activities of digestive (proteinases and lipases/esterases) and metabolic (citrate synthase) enzymes of copepods from all sampling stations were analysed and thermal profiles (5-50°C) of enzyme activities were determined. In order to investigate its acclimation potential, C. finmarchicus were acclimated to 4°C and 15°C for two weeks and thermal profiles of enzyme activities were compared afterwards.