Seawater temperature and carbonate chemistry controlled in the header tanks during the course of the experiment (∼14 days; n = 7).

Salinity was constant throughout the experiment at 34.5. Measured pH in the total scale (pHT), dissolved inorganic carbon (CT) as well as calculated pCO2 and saturation states with respect to aragonite (Ωaragonite) and calcite (Ωcalcite), are presented as mean, standard deviation (SD), minimal (Min) and maximal (Max) values.