Settling velocity of algal

Hello together, I have a question in terms of algal settling rate. Does the model consider the thermocline or is the the algal settling rate a constant factor? The problem is I don't reach the high oxygen concentrations in the metalimnion. This high oxygen concentrations (up to 20 mg/l) occur cause of lower vertical velocity (settling) and accumulation of algal in the metalimnion. Without algal the oxygen concentration increases somewhat in the range of the thermocline due to low vertical dispersion/diffusion. But If I assume an algal concentration the concentration-apex occurs above the thermocline. With many regards from Dresden (Germany), Michi