BIOGEN, a high trophic-resolution ecological model was applied by Lancelot et al., (2002) to the Black Sea system ( Figure 3.2(a)). This model was originally developed to track the impacts of altered nutrient discharges was also shown to produce consistent predictions on the effect of fishing intensity on the ecosystem structure.

BIOGEN, describes the carbon, nitrogen, phosphorus and silicon cycling throughout aggregated chemical and biological compartments of the planktonic and benthic marine systems, in the north-western Black Sea .

Particular attention was paid to establishing the link between quantitative and qualitative changes in nutrients, phytoplankton composition and food-web structures. The BIOGEN numerical code structure includes 34 state variables assembled in five interactive modules describing the dynamics of:

(1) phytoplankton, three groups diatoms, nanophytoflagellates, non-silicified opportunistic species.

(2) meso- and microzooplankton with high food selectivity.

(3) gelatinous organisms (omnivorous Noctiluca, carnivores Aurelia and Mnemiopsis) as trophic dead-end.

(4) planktonic and (5) benthic bacteria both responsible for organic matter degradation and associated nutrient regeneration processes.

Lancelot et al., (2002) present the first steps preliminary to the implementation of the 3-D BIOGEN:

1.- BIOGEN model coupled with a 1-D vertically resolved physical model

2.- BIOGEN model implemented as a two-box model resulting from the coupling between the 1-D vertically resolved open-area model and a volume-variable 0-D box model of the coastal area submitted to Danube inputs.