Nutrient mineralization rates and ratios in the eastern South Atlantic
Résumé
The physical and biogeochemical components of nutrients and inorganic carbon distributions along WOCE line A14 are objectively separated by means of a constrained least-squares regression analysis of the mixing of eastern South Atlantic water masses. Contrary to previous approaches, essentially devoted to the intricate South Atlantic circulation, this work is focused on the effects of circulation on nutrients and carbon biogeochemistry, with special emphasis on the stoichiometry and the rate of mineralization processes. Combination of nutrient and apparent CFC-age anomalies, derived from the mixing analysis, indicate faster mineralization rates in the equatorial (12 × 10−2 μmol P kg−1 yr−1) and subequatorial (5.3 × 10−2 μmol P kg−1 yr−1) than in the subtropical (4.3 × 10−2 μmol P kg−1 yr−1) regime at the South Atlantic Central Water (SACW) depth range. Lower rates are obtained in the Antarctic Intermediate Water (AAIW) domain (3.0 × 10−2 μmol P kg−1 yr−1). Significant variation with depth of O2/C/N/P anomalies indicates preferential mineralization of proteins in thermocline waters, as compared with the reference Redfield composition.