The response of three dominant Arctic copepod species to elevated CO2 concentrations and water temperatures

Ocean acidification (OA) and ocean warming are threatening marine life. Within the framework of the research project BIOACID, this thesis aims to provide a comprehensive overview on the sensitivity of the dominant Arctic calanoid copepod species Calanus finmarchicus, C. glacialis and C. hyperboreus to elevated pCO2 and temperatures. Controlled laboratory experiments have shown that subadult and adult Calanus life stages are rather robust to the direct effects of OA during both active and resting phases. A simultaneous increase of CO2 and temperature, however, induced stress in the copepods. Indirect effects of OA were studied in an ecosystem-scale mesocosm experiment. The copepods were mostly unaffected while the abundance of mollusc larvae decreased with increasing pCO2. OA-induced changes in the food regime might, however, severely affect Calanus in future decades, and future studies should focus on these indirect effects, also in combination with elevated temperatures.