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2I - High-tiered Studies (MO7/4) Lessons learned from the test phase of the new mesocosm system of the German EPA. Mohr, Silvia1, Feibicke, Michael1, Berghahn, Rüdiger1, Meinecke, Stefan1, Ottenströer, Thomas1, Schmidt, Ralf1, 1 Umweltbundesamt, Berlin, Germany ABSTRACT- In 2001, a new outdoor and indoor experimental system of lentic and lotic mesocosms has been put into operation by the German EPA in order to detect important system characteristics and technical limits during permanent operation. Within the 12-months test phase, a wide range of applications could be demonstrated. The system can easily be modified, loaded, operated and controlled according to experimental demands. The modular set up of the system consisting of 16 ponds and 16 artificial streams allows for fate and effect studies. Different types of lowland rivers, lakes and ponds including ground water contact can be simulated. Summer cold brooks and rivers, however, can only be simulated in the indoor system during winter due to relatively high water temperature in summer. Stocking effort of the indoor mesocosms with macro-invertebrates has to be higher and also more selective with regard to function as compared to the outdoor systems due to reduced colonization of insects. In the pools of the artificial stream system, some turbulence was introduced to allow for optimal growth of the introduced vascular plants. With regard to ecological synchronism of the systems some interesting observations were made which have to be considered in mesocosm studies in general: Very low levels of stray light in the indoor systems as well as slight differences in the mixing and loading of sediments can already have a strong negative effect. Furthermore, water mixing routines before starting effect studies are crucial for ensuring synchronous development of the replicates. Key words: artificial streams and ponds, mesocosm, ecotoxicology, synchronism |
