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Abstract:
Analysis of cladoceran remains taken from a sediment core of the northern German Plusssee showed a succession of Bosmina longispina, which have occurred since the Late-Glacial period, to a kessleri morph, which invaded in the Boreal period, and finally to Bosmina coregoni, which appeared in the late Subatlantic. This pattern seems to be typical of the deep lakes of the Holstein region. Using chirononomids as indicators of the trophic state, the three Bosmina zones roughly coincided with the oligotrophic, mesotrophic and eutrophic phases of lake development. The kessleri and coregoni morphs were connected by a continuous line of morphological variation due to successive reduction in mucro length. There was no morphological indication of hybridization between B. longispina and the kessleri morph, which clearly differs from the development observed in Lake Constance.
