Simulating phytoplankton community dynamics in Lake Constance with a coupled hydrodynamic-ecological model

Lake Constance is among the largest lakes in central Europe and represents the most important drinking water reservoir in southwestern Germany. About 4 million people depend on this lake for their drinking water supply, and considerable efforts have been made to protect its high water quality (STABEL 1998). In addition to a drinking water supply, the lake is the receiving water body of numerous waste-water plants within its catchment and is moreover used for recreational purposes and fisheries. To improve water quality management of the lake, a research project (see www.bodenseeonline.de) was initiated to develop a model-based decision support system. The model system consists of a coupled hydrodynamic ecological model that can be either run in a 1D-setting (DYRESM-CAEDYM) or a 3D setting (ELCOM-CAEDYM). The establishment of the model systems requires the adaptation of the ecological model CAEDYM to Lake Constance, achieved by long-term simulations and comparison to historical data. The main goal of this study is to adapt the ecological model to reflect the physiological properties of the planktonic community, particularly for phytoplankton, which shows a great functional diversity. This diversity needs to be taken into account (REYNOLDS et al. 2002, SOMMER et al. 1986) for phytoplankton succession to be represented properly.