Eric von Elert

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A key process in freshwater plankton food webs is the regulation of the efficiency of energy and material transfer. Cyanobacterial carbon (C) in particular is transferred very inefficiently to herbivorous zooplankton, which leads to a decoupling of primary and secondary production and the accumulation of cyanobacterial biomass, which is associated with(More)
In food-web studies, parasites are often ignored owing to their insignificant biomass. We provide evidence that parasites may affect trophic transfer in aquatic food webs. Many phytoplankton species are susceptible to parasitic fungi (chytrids). Chytrid infections of diatoms in lakes may reach epidemic proportions during diatom spring blooms, so that(More)
Two major biological stressors of freshwater zooplankton of the genus Daphnia are predation and fluctuations in food quality. Here we use kairomones released from a planktivorous fish (Leucaspius delineatus) and from an invertebrate predator (larvae of Chaoborus flavicans) to simulate predation pressure; a microcystin-producing culture of the cyanobacterium(More)
Two major protease activities were present in gut homogenates of the cladoceran crustacean Daphnia magna: (i) a trypsin activity that hydrolysed the synthetic substrate N-benzoyl-dl-arginine p-nitroanilide and was strongly inhibited by N-p-tosyl-lysine chloroketone (TLCK) and 4-(amidinophenyl)methanesulfonyl fluoride (APMSF) and not inhibited by(More)
The frequency of cyanobacterial blooms has increased worldwide, and these blooms have been claimed to be a major factor leading to the decline of the most important freshwater herbivores, i.e. representatives of the genus Daphnia. This suppression of Daphnia is partly attributed to the presence of biologically active secondary metabolites in cyanobacteria.(More)
Anthropogenic nutrient input into lakes has contributed to the increased frequency of toxic cyanobacterial blooms. Daphnia populations have been shown to be locally adapted to toxic cyanobacteria and are able to suppress bloom formation; little is known about the physiology behind this phenomenon. Microcystin-LR (MCLR) is the most widespread cyanobacterial(More)
A new depsipeptide, cyanopeptolin 954 (1), was isolated from the freshwater cyanobacterium Microcystis aeruginosa NIVA Cya 43. The structure of the compound was elucidated by chemical and spectroscopic analyses, including 2D NMR and GC-MS of the hydrolysate. The major structural differences compared to previously characterized heptadepsipeptides of(More)
Daphnia has been shown to acquire tolerance to cyanobacterial toxins within an animals' lifetime and to transfer this tolerance to the next generation. Here we used a strain of the cyanobacterium Microcystis aeruginosa, which contained two chymotrypsin inhibitors (BN920 and CP954), the green alga Scenedesmus obliquus as reference food and a clone of D.(More)
Experimental results provide evidence that trophic interactions between ciliates and Daphnia are constrained by the comparatively low food quality of ciliates. The dietary sterol content is a crucial factor in determining food quality for Daphnia. Ciliates, however, presumably do not synthesize sterols de novo. We hypothesized that ciliates are(More)
A significant seasonal variation in size at settlement has been observed in newly settled larvae of Dreissena polymorpha in Lake Constance. Diet quality, which varies temporally and spatially in freshwater habitats, has been suggested as a significant factor influencing the life history and development of freshwater invertebrates. Accordingly, experiments(More)