CARBONATE SYSTEM IN THE WATERS NEAR THE GALAPAGOS-ISLANDS

During the IRONEX cruise in the equatorial Pacific Ocean, the carbonat e parameters, TA (total alkalinity), TCO2 (total inorganic carbon), pH and fCO(2) (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 Gal apagos Islands. The CO2 parameters, along with hydrographic properties , were found to be uniform in the surface waters of the study area bef ore the addition of iron. A significant decrease of the surface TCO2 ( 7 mu mol kg(-1)) and fCO(2) (11 mu atm) in the patch was detected with in 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 mu mol kg(-1)) and complete consumption of the nutrients. A good correlation was fou nd between TCO2, pH and fCO(2) with temperature in the surface waters around the Galapagos Islands. The salinity (S = 35) normalized alkalin ities 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 CO 2. (C) 1998 Elsevier Science Ltd. All rights reserved.