In order to have realistic variations of the internal C:N ratios of the mesozooplankton, we explicitly took into account the metabolism of carbon respiration, nitrogen excretion as well as the nitrogen quota parameters (table 1). By decoupling the metabolism of nitrogen from the metabolism of carbon, we allowed the accumulation of the latter. Then we used two different C:N thresholds (table 1) in order to trigger the entry or the exit of diapause. Following in-situ data, Calanus species in early diapause usually have a C:N ratio of 12 whereas late diapausing species have a C:N of 6.5 (Forest et al. 2011). Since DARWIN is an Eulerian model, we created a “mirror” community for each functional copepod-like species. This mirror community was the “in-diapause” state of the active community. By doing so, as soon as a community had to go into diapause, its biomass would be transfer to its mirror/diapause community and vice-versa.