The chemical equation for the oxidation of the organic matter [C₁₂₉H₂₃₄O₇₀N₁₇P] + 175 O₂ + 148 CO₃⁼ + 22 H₂O: 277 CO₃H^- + 17 NO₃^- + PO₄H⁼ is established, starting from the elemental composition of phytoplankton. This equation allows calculation of the coefficients for the parameters “NO”, “PO” and “CO”. These coefficients are respectively 10.3, 175 and 1.36. Corrections of the equations for the calculation of “NO”, “PO” and “CO” have been added so that they may also be used in waters when nitrite and ammonia concentrations and precipitation or resolution of calcium carbonate are high. The Redfield ratio DP:DN:DC:-DO₂ = 1:17:129:175 is also obtained starting from the same data.