The long-term dynamics of crustacean communities in Lake Constance (Obersee, 1962–1986) |
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| Authors: | Ulrich Einsle |
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| Institution: | 1. Landesanstalt für Umweltschutz Baden-Württemberg, Institut für Seenforschung und Fischereiwesen, Au?enstelle Konstanz, Schiffstra?e 56, D-7750, Konstanz-Staad, Germany
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| Abstract: | The long-term development of crustacean associations in the Obersee of Lake Constance was studied at one central station from
1962 to 1986. In a simultaneously managed program with four additional stations from the eastern part (Bregenz Bay) to the
western überlinger See mainly the differences in horizontal distribution were focussed. It was one aim of these investigations,
to get an idea or an indication of a connexion between the recently observed eutrophication of the Obersee, and its crustacean
communities.
Due to the immigration of several species (cyclopids) or genotypes (Daphnia), the communities had changed in genetical structures, in reproduction rates and in predation or grazing impact. Dependent
on the specific annual cycles, there resulted an extermination (Heterocope, Diaphanosoma), or a long-term decrease in annual means (Mesocyclops, Cyclops abyssorum) of the “old-settled” species.
A general tendency was seen in an increase of annual averages until the middle of the seventies, and a following decrease
of population density of most of the species.
The horizontal differences in the species associations were remarkable. The Bregenz Bay showed an own aspect in its crustacean
community with high total numbers and in earlier spring development. Most of the newcomers were concentrated in the eastern
part of the lake. |
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