Improved calibration of a eutrophication model by use of the size variation due to succession

Ecological models may be considered synthesis of our knowledge about a question (problem) associated with an ecosystem. As we know that ecosystems are adaptable systems and are able to shift the species composition, it may often be important that these processes are included in the development of an ecological model. They can be described by optimization of exergy, which have been used successfully to set up prognoses based on ecological models in 13 case studies, in the sense that the models were able to describe the observed change in properties of the core organisms. It would therefore be obvious to examine if the method could also be used to improve the calibration of models. Modellers of very dynamic ecosystems, for instance lakes or rivers, have the experience that it is often very difficult to calibrate the model because one set of parameters cannot fit to the observations that are based on seasonal changes in the species composition, the so called succession. It has been examined whether variable parameters based on a current optimization of exergy and describing the succession would yield a better calibration. The results show that it is, at least in the currently examined case study, possible to improve the calibration by this method. Therefore, it is recommended to test the method further for a later incorporation into a modelling routine. (C) 2002 Elsevier Science B.V. All rights reserved.