Toxic Blue‐green Algae Water Blooms Found in some Lakes in the German Democratic Republic

From 1977 to 1979 plankton samples were taken from 6 lakes in the German Democratic Republic (GDR) during water blooms and examined for their toxicity to homothermal animals. Microcystis aeruginosa, Aphanizomenon flos‐aquae, Anabaena spiroides, and Oscillatoria redekei were dominant in the samples. With the exception of Oscillatoria redekei the algae tested had toxic effects on mice after intraperitoneal injection. The rate of survival of the test animals was particularly low when the algae were disintegrated by ultrasound or freeze‐drying prior to injection, this indicating the endogenic character of the toxins. Water blooms of Microcystis aeruginosa taken from Lake Pehlitzsee (Eberswalde District) showed the highest toxicity with an LD30 as high as 45 and 43.7 mg/kg, respectively. Injection of the lyophilized cells of Aphanizomenon flos‐aquae brought about the same symptoms in the test animals as in the case of Microcystis, but the LD30 was 200 mg/kg.