Lake Glumso: Case Study on Modelling a Small Danish Lake

The case study on the small Danish post-glacial Lake Glumso shows some of the highlights of aquatic ecosystem research over the time span of more than 30 years. The research at Lake Glumso is closely linked to the development of ecological modelling as a discipline, inspired a wide range of related working approaches as well as advancements in ecological modelling and the development in ecological theory. In the early working phase, models based on differential equations were used not only to describe the lake processes but also to methodologically identify the optimal formalisation of the described processes. First, modelling applications were continuously improved, thus providing a large body of functional representations for the different compartments. A result of the intense discussions of the early model structures was a new approach called structural dynamic modeling which allowed for varying numbers of variables and a model structure that could change during simulation time. Continuing the search for optimal trade-off between model complexity on one side and efficiency and precision on the other side, machine learning techniques were applied to find out, whether this could help to identify the most reasonable model structures which were tested with Lake Glumso data and many other lakes world wide. In further contributions to ecological theory, the question was tackled whether overall ecosystem characteristics, like exergy, biomass production or species composition, do converge in a successional process towards optimal values. This led to the development of ecosystem goal functions, which was part of an international ecosystem research debate on the theoretical patterning and the dynamics of ecosystems. Collaborating research groups on ecosystem research benefited very much from the experiences made and the knowledge gained from the Lake Glumso studies.