Independent impacts of calcium and carbonate ion concentration on Mg and Sr incorporation in cultured benthic foraminifera

► The authors cultured two benthic foraminifers at different carbonate ion concentrations. ► Resulting saturation states (Ω's) did not affect calcitic Mg/Ca and Sr/Ca. ► Changing Ω by altering calcium concentrations, however, impacted calcitic Mg/Ca. ► These sensitivities are similar for species with contrasting Mg/Ca. ► Inorganic carbon and calcium are likely processed separately for calcification.