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 (8×8 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 NO-3 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.