Average (± SE) conditions of the seawater used to maintain C. concholepas during the acidification phase (July to October 2011).

pH (total scale), Total alkalinity (TA in µmol kg−1), partial pressure of CO2 (levels of pCO2 in µatm), Carbonate ion concentration (CO32− in µmol kg−1), saturation states of the water in terms of aragonitic and calcite minerals (Ωaragonite and Ωcalcite respectively). The different experimental levels of pCO2 in the mesocosms and in the rearing containers were achieved and maintained during the entire experimental period by active injection of CO2 and air (see Materials and Methods for further details).¥Based on rate of change in pH predicted by the most extreme scenario (RCP8.5 scenario) of atmospheric CO2. See Meinshausen et al. 2011.