Jürgen Benndorf

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Since indirect effects, feedback mechanisms and time lag play an important role in top-down manipulated food webs, conclusions regarding the reliability of biomanipulation as a management tool should be derived only from whole-lake studies, the results of which were followed for at least three to five years. There are only a few experiments and applications(More)
The results of long-term, full-scale experiments in biomanipulation (in the closer sense of top-down control of the food web) in water bodies having extremely different phosphorus loads reveal that there is a close connection between the efficiency of food web manipulation and the nutrient situation in the particular water body. Top-down control provides a(More)
Temperature-driven changes in interactions between populations are crucial to the estimation of the impact of global warming on aquatic food webs. We analysed inter-annual variability in two data sets from Bautzen reservoir, Germany. In a long-term data set (1981–1999) we examined the pelagic phenology of Daphnia galeata, a keystone species, the(More)
In Bautzen Reservoir (Germany), a technique of internally dosing iron compounds in combination with a local water column destratification was developed in order to control Microcystis blooms. In this paper, experimental results concerning the phosphorus (P) precipitation by iron application are reported. First, preliminary studies were conducted serving the(More)
Batch culture experiments with the cyanobacterium Microcystis aeruginosa PCC 7806 were performed in order to test the hypothesis that microcystins (MCYSTs) are produced in response to a relative deficiency of intracellular inorganic carbon (C(i,i)). In the first experiment, MCYST production was studied under increased C(i,i) deficiency conditions, achieved(More)
In Bautzen reservoir, a shallow, hypertrophic water in Eastern Saxony, biomanipulation led to structural changes in the phytoplankton community but did not reduce algal biomass. To supplement the top-down management, a new type of water treatment technology was tested during two seasons (May–August 1996/1997), aiming at the bottom-up control of mass(More)
We studied the response of phytoplankton to grazing by Daphnia galeata in the hypertrophic Bautzen reservoir (Dresden, Germany) from January 1995 to May 1996 during a long-term whole-lake biomanipulation experiment. The correlation between clearance rate of D. galeata and total phytoplankton biomass was negative only if biomass of Microcystis aeruginosa was(More)
Predation by perch (Perca fluviatilisL.) and zander (Stizostedion luciopercaL.) on their new-hatched fish was studied in the littoral and pelagic zone in the biomanipulated Bautzen reservoir (Germany). Sampling was conducted from the middle of May to the middle of August in 1997. To investigate predation, we compared the littoral and pelagic zone, because(More)
Drift as a low-energy cost means of migration may enable stream invertebrates to leave risky habitats or to escape after encountering a predator. While the control of the diurnal patterns of invertebrate drift activity by fish predators has received considerable interest, it remains unclear whether benthivorous fish reduce or increase drift activity. We(More)