Über den Einfluß von fädigen Cyanobakterien auf Zooplankter (Cladoceren, Copepoden) / eingereicht von Rainer Kurmayer

• VerfasserIn: Kurmayer, Rainer
• Place / Publishing House: [1999]
• Year of Publication: 1999
• Language: German
• Physical Description: 155 Bl.; graph. Darst.
• Notes: Zsfassung in engl. Sprache

eng: Zooplankton may coexist with filamentous cyanobacteria or may be inhibited by toxicity, low nutritional quality or mechanical interference with feeding due to the large size of the particles. The present study investigates potential factors modifying the response of zooplankton to a dominance of filamentous cyanobacteria. The effects of the availability of high-quality food sources on the response to filamentous cyanobacteria were studied with cladoceran species of different body sizes. The cladocerans were grown under limited (0.1 mg carbon/l) or unlimited (1.0 mg carbon/l) concentrations of high-quality food algae each in the absence or presence of various concentrations of non-toxic (Anabaena, Aphanizomenon flexuosum) and toxic (Planktothrix rubescens) filamentous cyanobacteria (1,000 - 10,000 filaments/ml). Daphnia spp. was affected by the filamentous cyanobacteria via nutritional quality or toxicity whereas the small cladocerans (Ceriodaphnia reticulata, Bosmina longirostris) were affected by mechanical interference with the collection of available food sources. For both, Daphnia and small cladocerans the degree of inhibition varied considerably between food concentrations. Consequently, food availability should be considered when assessing the impact of cyanobacteria in the field. The effects of the toxic cyanobacterium Planktothrix rubescens on co-occurring zooplankton were studied in the light of co-evolved herbivore interactions. High sensitivity to toxins of Planktothrix was coupled to strict food avoidance in Eudaptomus gracilis. Daphnia hyalina and Cyclops abyssorum exhibited higher physiological resistance to the toxins and ingested Planktothrix. Daphnia hyalina also exhibited higher resistance to toxic cyanobacteria when compared with non- adapted Daphnia species. For both, Daphnia and copepods the grazing resistance of Planktothrix was mediated by chemical defenses rather than by the large size of the filaments.