The aim of this research project is to analyse the physiological response of an active calcifier (bivalves) to ocean acidification (OA) and ocean warming on the organismic and cellular level. The work is based on a comparison between temperate (Pecten maximus) and sub-arctic (Chlamys islandica) pectinids. We investigate the effect of different OA scenarios (390, 750, 1120 ppm CO2) at two different temperature regimes (long-term acclimation to mean habitat and elevated temperature). The incubation of C. islandica and P. maximus at 0°C and 10°C, respectively, started using a re-circulated system. Preliminary results obtained on C. islandica after long-term incubation at 390 and 1120 ppm CO2 (≥8 weeks) suggest that OA has no impact on routine metabolism of the animals. Following exhausted exercise metabolic rate rose by a factor of ~2 in both groups indicating again similar rates in control and OA-exposed animals. Further analysis of aerobic and anaerobic metabolites during recovery phase will be conducted using NMR spectroscopy. Tissue samples from different organs will be taken for a mostly complete metabolic analysis (e.g. muscle, mantle, gill) and hemolymph pH will be measured. Energy dependent cellular processes such as ion regulation, protein synthesis will be determined by on-line profiling using Bionas® analyzing system.