The main goal of the master’s thesis was to investigate the influence of various
zooplankton taxa on the structure of phytoplankton community according to va-
riations in nutrient concentrations. A system of 35 mesocosms with 7 different
treatments was established on the Klostersee lake and filled with zooplankton
taxa from it. Experiment was performed from 14.7. to 2.8.2021, where nutrients,
phytoplankton and zooplankton were sampled and later analyzed. Nutrients and
phytoplankton were sampled in the mornings with the integrated sampler from 4
m and 1 m depth. Zooplankton was towed in the night time from 4 m depth. We
found that the frequency of cyanobacteria (Cyanophyta) increased due to selec-
tive grazing of the herbivorous taxa Eudiaptomus gracilis. The greatest decrease
of the phytoplankton density (herbivore predation) was in the treatments domi-
nated by Cladocera taxa and Cladocera taxa combined with Copepoda taxa. In
the treatments with carnivore taxa Chaoborus spp., the Copepoda taxa was less
preyed compared to the Cladocera taxa. A decline in the silica concentration and
later diatoms was noticed.
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