Zooplankton succession and thermal stratification in the polymictic shallow Muggelsee (Berlin, Germany): a case for the intermediate disturbance hypothesis?

From the end of May to November 1995 the succession of rotifers and cladocerans was investigated in Muggelsee with samples taken twice a week. Keratella cochlearis was the only rotifer which was found on every sampling day and this species also showed the highest abundances. During summer, when frequencies of strong wind events were low and water was strongly stratified, three small cladocerans were dominant (Daphnia cucullata, Chydorus sphaericus, Eubosmina coregoni). Food supply was the main limiting factor for Keratella spp. and Synchaeta spp. In autumn, however, when the intervals between strong winds were shorter, rotifers with shorter periods for population development prospered. Zooplankton diversity first increased and subsequently decreased after disturbances. The results do not support the intermediate disturbance hypothesis in its present formulation.