Carbonate system in the waters near the Galapagos Islands

During the IRONEX cruise in the equatorial Pacific Ocean, the carbonate parameters, TA (total alkalinity), TCO₂ (total inorganic carbon), pH and fCO₂ (fugacity of CO₂), were determined both in a small (8 x 8 km) patch of water fertilized with Fe and in the waters around the Galapagos Islands. The CO₂ parameters, along with hydrographic properties, were found to be uniform in the surface waters of the study area before the addition of iron. A significant decrease of the surface TCO₂ (7 μmol kg^-1) and fCO₂ (11 μatm) in the patch was detected within 48 h of the iron release. This decrease, however, did not continue and was lower than expected from the complete utilization of NO₃/^- due to the addition of iron. The shipboard iron addition experiments (3 nM Fe) resulted in a continual decrease of TCO₂ (up to 48 μmol kg^-1) and complete consumption of the nutrients. A good correlation was found between TCO₂, pH and fCO₂ with temperature in the surface waters around the Galapagos Islands. The salinity (S = 35) normalized alkalinities were quite uniform (NTA = 2310 ± 9 mol kg^-1) throughout the region. The effect of high primary production on the CO₂ system in the downstream plume is overshadowed by the upwelling waters with high CO₂.