Shallow Lakes - Balatonfüred, Mai 25th-30th, 2002.
Oral presentation : Typology and ecological assessment of lakes in Brandenburg (North-East Germany) based on macrozoobenthos fauna. Garcia XF, Pusch M, Walz N.
In the European Water Framework Directive (2000) a complex assessment of the ecological quality of lakes is required from the members of the European Community. For that purpose, we investigated the benthic invertebrates colonizing 30 lakes in the land of Brandenburg, north-east Germany.
Two aims are pursued : (1) Definition of a typology of the 30 lakes based on the colonisation of littoral and profundal zones by the macrozoobenthos, and identify the biological communities associated to each type of lakes. (2) Development of an assessment scheme for the ecological state of the lakes, based on the structure of the benthic fauna actually found in the lakes. This includes the description of reference conditions, too. Our paper gives the first results of this study.
In each lake, macrozoobenthos was sampled with 6 replicates both in the littoral zone, using a hand-net sampler, and in the profundal zone using a grab sampler. Statistical analysis of the data was done with multivariate ordination methods, cluster analysis and Hasse-diagram techniques.
Preliminary results clearly separate lakes formed by the Weichsel and Saale glaciation periods. The geologically younger lakes formed after the Weichsel glaciation period in the north part of Brandenburg exhibit more diversified bank habitats which are often free of organic deposits. Some lakes comprise a high biodiversity, with a high percentage of rare and uncommon species. Morphometry appears to be an other key factor for the typology of the lakes, especially the depth, as the very shallow lakes less than 4 meter depth are colonised by richer assemblages of species. Also, the connection of the lake with a river influences the composition of its fauna.
The profundal fauna of the lakes is significantly influenced by the trophic status of the lake, while the littoral fauna is largely influenced by the structure of riparian vegetation and land use. The differences in the indicative value of these two invertebrate assemblages enable to distinct between trophic status and structural influences on lake fauna.