Figure 5.

Four plots showing carbonate system parameters recovered from the calcifying fluid: (a) pH_cf calculated from δ¹¹B, as is clear from the raw data the pH is elevated in the wall compared to the columella, though both show an annual cycle and sub-annual features are visible within the walls; (b) carbonate ion [CO₃²⁻]_cf calculated from δ¹¹B and B/Ca, similar to pH_cf, carbonate ion is elevated in the walls and shows an annual cycle; (c) aragonite saturation state calculated using δ¹¹B and B/Ca data, as expected from pH_cf and [CO₃²⁻]_cf the saturation state is higher in the denser material of the walls, and tending towards seawater values at the centre of calcification; (d) bicarbonate (µmol/kg) calculated from δ¹¹B and B/Ca. For further details see “Materials and methods” section.