The study addresses various aspects of model-based estimating the oceanic primary production. In particular, we consider existent interpretations of the export fluxes; influence of implied conversions between modelled chlorophyll and biomass, expressed in nitrogen and/or carbon units, and, therefore, impact of decoupling the biogeochemical (N, C) cycles and chlorophyll. The export production is estimated by simulating global ocean biolgeochemical dynamics with the CN regulated model (REcoM) developed by Schartau et al. (2007) and coupled with the MITgcm. The model describes carbon (C) and nitrogen (N) fluxes between components of the ocean ecosystem. The nitrogen and carbon cycles as well as phytoplankton chlorophyll (Chl) dynamics are decoupled in accordance with the dynamic regulatory phytoplanktonic acclimation model sugested by Geider et al. (1998). Sensitivity of the primary production estimates to biological model parameters is also discussed.