Author(s)

SVEN ERIK JØRGENSEN

Abstract

Lakes as all other ecosystems are adaptive, have self-organization, and change the species compositions in accordance with the variable forcing functions. Therefore, models that can capture this dynamics are needed, which means that the properties (represented in models by the parameter) of the biological components of the model are continuously changed. This paper presents what is denoted as structural dynamic models (SDMs) that can capture this dynamics of changing the ecosystem structure. A SDM uses a goal function to determine the changes of the parameters. Eco-exergy is used as goal function, which is the work capacity (work energy) of the ecosystem. The use of this goal function can be considered a translation of Darwin’s theory to thermodynamics. In 23 case studies, it has been possible to use SDM to describe the structural changes with an acceptable standard deviation. Of these cases, 12 were lake models and an attempt is made in this paper to summarize the experience gained by the use of SDMs on lakes. The three most characteristic case studies are presented in more detail and conclusions on the applicability of SDM on lakes are summarized.

Keywords

Adaptation, eco-exergy, lake models, shift in species composition, structural dynamics