Structural dynamic model

Abstract The need for structural dynamic models is discussed and demonstrated. It is suggested to build this type of model by use of simple models, where the parameters are currently changed by a control function. The thermodynamic function energy is introduced as a possible and ecologically sound control function. Results by the use of energy as a control function demonstrate that it gives expected results. Significant improvement of a prognosis based upon a eutrophication model was obtained in a case where a shift in phytoplankton species composition was observed.