The role played by the natural organic ligands excreted by the green algae Dunaliella tertiolecta on the Fe(II) oxidation rate constants was studied at different stage of growth. The concentration of dissolved organic carbon increased from 2.1 to 7.1 mgL-1 over time of culture. The oxidation kinetics of Fe(II) was studied at nanomolar levels and under different physico-chemical conditions of pH (7.2-8.2), temperature (5-35ºC), salinity (10-37) and dissolved organic carbon produced by cells (2.1-7.1 mgL-1). The experimental rate always decreased in the presence of organic exudates respect to that in the control seawater. The Fe(II) oxidation rate constant was also studied in the context of Marcus theory, where ∆Gº was 39.31-51.48 kJmol-1. A kinetic modelling approach was applied for computing the equilibrium and rate constants for Fe(II) and exudates present in solution, the Fe(II) speciation and the contribution of each Fe(II) species to the overall oxidation rate constant. The best fit model took into account two acidity equilibrium constants for the Fe(II) complexing ligands with pKa,1=9.45 and pKa,2=4.9. The Fe(II) complexing constants were KFe(II)-LH=3∙1010 and KFe(II)-L=107 and the corresponding computed oxidation rates were 68±2 and 36±8 M-1min-1, respectively.