Impact of parameter choice on the dynamics of NPZD type ecosystem models

Marine ecosystem models of NPZD type are analyzed to identify model specific dynamics in dependence on the parameter setting used. It is shown that detecting the equilibria of a model and computing the eigenvalues of its linearizations it is possible to completely determine its dynamics. Three related model formulations are analyzed this way. Based on analytical computations for the simplest formulation, a theoretical classification of the occurrence of specific dynamics is presented. Its significance for all three model formulations is examined using numerical methods. Further, dynamical characteristics arising from the enhancemet of complexity in the model formulation are examined. Similarities and differences of the three models are pointed out. The most significant dynamical discrepancy is that the simplest model formulation shows limit cycles while this feature does not appear in the other two models. The results presented in this study show that knowing the basic dynamics of a model its valid application can be ensured.