Nutrients and grazing in modeling the deep chlorophyll maximum

A representation of nutrients uptake and grazing processes, based on the specific uptake rate of multiple nutrients and specific predation rate in 1-predator_n-prey systems, is applied to a model for simulation of deep-chlorophyll maximum (DCM) in seas. In the original model a formulation for uptake processes was obtained from a mononutrient system. A detailed analysis of differences between the original and a modified model is performed. The modification increases the peak, but does not change the depth of DCM. Replacing the expression for grazing processes contributed to the differences between results more than a change in the uptake formulation. This is a consequence of two facts, (a) nutrient cycling plays a secondary role in the model, making nitrate dominant and ammonium a superfluous variable; while (b) prey concentrations are closer to their half-saturation constants. Since the original model was calibrated using improper formulations in uptake and grazing processes, a new calibration was performed.