calibration of oxygen

Hello there, I try to calibrate dissolved oxygen. The measured data show in spring/summer a dissolved oxygen maximum in the metalimnion (18 - 20 g/m³ - this is characteristic for nutrient-poor lakes and it depends on the depth of visibility. One year there was a high oxygen demand in the metalimnion because the solar radiation did not permeate - the depth of visibility in this year was only 1-2 m (in summer). But in the majority of cases there were an oxygen accumulation in the metalimnion). In the vertical profile file I have added algae and phosphor concentration but the model does not simulate the measured dissolved oxygen concentrations. The calibration of temperature was successful. Maybe the initial concentration of algae is to small - is it right, that I multiply the factor 64 by the measured chlorophyll? Where does the factor originate? I should like to point out that the lake is a mining lake and is in the phase of stabilization. best regards, Michi