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内容記述 |
Cyanobacterial blooms in eutrophic lakes often produce algal toxins causing death of livestock, wild animals, and fish. In this work, phytoplankton communities were examined for the appearance of toxic species. The occurrence of toxic bloom was examined with mouse bioassay. Phytoplankton were collected in late summer at the surface of 6 middlestream reservoirs(Soyang, Chungju, Daechong, Jangsung, Hapchon, Jinyang, Okjung), an estuarine reservoir(Yongsan), and a coastal lagoon(Yonglang). Algal cells were freeze-dried for the use in mouse bioassay and chemical analysis. The occurrence of toxic bloom was examined with mouse bioassay and the content of two cyanobacterial hepatotoxins, microcystin-RR and -LR, that are known to be most common in freshwater algae were analyzed with HPLC. In all the study lakes cyanobacteria were dominant phytoplankton. The dominant species implied the possibility of toxin production(Microcystis, Anabaena etc.). In L. Soyang and Chungju, dominant species were Anabaena and Oscillatoria, respectively. In L. Jangsung and Daechong, Anabaena and Microcystis appeared together. Test of toxicity by mouse bioassay showed lethal effect for L. Yonglang, L. Hapchon, L. Yongsan, L. Jangsung. L. Yonglang showed strong lethal effect. Microcystin-LR and -RR both were detected in L. Hapchon, L. Jangsung and L. Yonglang, and microcystin-LR was detected in L. Yongsan, -RR was detected in L. Daechong, L. Chungju, and L. Soyang. |