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Inhibitory and Toxic Effects of Blue‐green Algae on Daphnia
Author(s) -
Lampert Winfried
Publication year - 1981
Publication title -
internationale revue der gesamten hydrobiologie und hydrographie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.524
H-Index - 52
eISSN - 1522-2632
pISSN - 0020-9309
DOI - 10.1002/iroh.19810660302
Subject(s) - microcystis , aphanizomenon , microcystis aeruginosa , daphnia , biology , scenedesmus , algae , botany , cladocera , cyanobacteria , food science , green algae , bacteria , ecology , anabaena , zooplankton , genetics
The effects of the planktonic blue‐green algae, Aphanizomenon gracile, Synechococcus elongatus , and Microcystis aeruginosa , on survival, growth, and food uptake of Daphnia pulicaria were determined. Synechococcus and Aphanizomenon were unsuitable food when offered alone, but did not affect the daphnids negatively when mixed with Scenedesmus. Microcystis was the only one found to be toxic. In pure suspensions of this blue‐green, the daphnids did not survive more than 48 hours; they lived a little longer if Scenedesmus was supplied additionally. Growth was markedly reduced when only 50 μg carbon/l of Microcystis was added to the normal Scenedesmus food. It ceased at a concentration of 250 μg C/l. This can be explained by the reduction of food uptake. Very small quantities of Microcystis (10 μg C/l) present in the normal food caused a significant reduction of the filtering rate. Filtering inhibition was associated with the cells. Filtrate of Microcystis suspensions was not effective. Thus, the daphnids must ingest the blue‐green cells in order to become toxified. Dual‐labelling experiments showed that Microcystis cells are filtered from the medium by Daphnia with the same efficiency as Scendesmus and are not rejected. Toxicity of Microcystis is considered to be an effective defence mechanism against grazing pressure.