Global change is expected to alter hte physical conditions in lakes. This project will develop a plankton succession model and combine it with a 1 dimensional physical model to investigate the effect of changes iin the physical environment and specifically in water temperature on plankton succession. In the two year application period the plankton succession model proposed will be focused on phytoplankton and <it>Daphnia</it>, because phytoplankton abundance is mainly determined by the availability of nutrients and light, whereas <it>Daphnia</it> growth is highly sensitive to water temperature. The plankton succession model will also include in a simplified fashion fast growing microzooplankton feeding on phytoplankton and the predation of fish on <it>Daphnia</it>. Sub-models resolving different details (e.g. size structure, stoichiometry) of <it>Daphnia</it> development will be included to investigate the importance of model detail on the overall model behaviour with respect to field observations. <p> Model calibration and validation will be based on the extensive data set available for Lake Constance. Comparison of data and model results on the plankton succession in years with extreme thermal conditions will be used to investigate whether the impact of changes in the physical environment on plankton succession can be adequately simulated and possibly leads to a shift in the interactions within the plankton community (match-mismatch). Because the ecosystem in spring and early summer is very sensitive to external forcing and dominated by only a few species, the main part of the investigations will initially concentrate on spring and early summer. Consequences of global warming on the physical parameters and the implications on the plankton succession will be studied using numerical experiments. <p> The modeling work will be complemented by field measurements during late winter and early spring to provide data with a better temporal resolution on the plankton development, ant to improve the data quality for especially daphnids, which is rather poor in the existing data base set because only few individuals were obtained within zooplankton sample. <p>
Depending on the outcome of modeling work during the two application period we will apply the plankton succession model to study other time periods of the year, other lakes, mesocoosms or extend the model by considering additional species.