2. Does the sulfur content of calcite microfossils reflect seawater [CO3=]?
The [SO4=] concentration of seawater is constant
The [CO3=] concentration of seawater varies with pH and total dissolved inorganic carbon dioxide.
Hence the [SO4=]/ [CO3=] ratio of seawater is variable.
When calcite microfossils are formed (incorporating ~0.1% of SO4= into CaCO3), do they reflect the [SO4=]/ [CO3=] of the seawater the organisms grow in?

6. Little Bahama Bank Field Calibration

7. The normalized SO42- values to a constant Mg content yield SO42- profile, which is negatively correlated with CO32- as expected.