THE SHIFTS IN SPECIES COMPOSITION AND ECOLOGICAL MODELING IN HYDROBIOLOGY

Ecosystems have an enormous flexibility to meet changes in external factors and still maintain their functions. If present species are not able to cope with the conditions, given by the external factors, new species are waiting in the wings ready to take over. It is a serious shortcoming of our present ecological models, that they are not able to describe these changes in species composition. However, it seems that the thermodynamic function exergy may be used as goal function in ecological models to incorporate the flexibility of real ecosystems and the selection of species into our models of ecosystems. The application of exergy in modelling may be considered a translation of Darwin's selection into thermodynamics. The theoretical basis for the application of exergy as goal function is presented, and applications of exergy in ecological models are illustrated by several case studies.