Fig. 4.

Changes in bulk and near-cell (proximal) [H⁺] for CM and phytoplankton. These are shown for the 300 atm pCO₂ scenarios. The “small” cell versions are the same as shown in Fig. 3 and Supplementary material Figs S4 and S5, with an average cell ESD of 20 μm. The “large” cells have an average ESD of 250 μm. Growth is simulated in a light:dark cycle, with the latter 0.3 of each day in darkness, hence the increase in [H⁺] at that time period, as respiration exceeded photosynthesis.