Preliminary characterization of neurotoxic cyanobacteria blooms and strains from Finland

Two hundred fifteen cyanobacteria bloom samples collected from different parts of Finland were studied, 35 of which proved to be neurotoxic. Toxicity was determined by mouse bioassay. Anabaena species were present in all neurotoxic samples except one, in which Oscillatoria dominated. The presence of anatoxin‐a in the blooms and in the isolated strains was studied from freeze‐dried materials by gas chromatography/mass spectrometry. The simultaneous occurrence of neurotoxicity and hepatotoxicity in some samples was studied by high performance liquid chromatography and high performance thin layer chromatography. Thirteen out of 30 bloom samples contained anatoxin‐a. In the remaining samples, neurotoxicity was caused by unknown toxin(s). Strains producing anatoxin‐a were isolated from the genera Anabaena, Aphanizomenon, Oscillatoria, and Cylindrospermum. Anatoxin‐a content of the blooms varied from 12 to 4360 μg/g freeze‐dried material. Some strains were able to produce about three times as much anatoxin‐a as was detected in natural blooms. Simultaneous occurrence of neurotoxicity and hepatotoxicity was found in some samples as well as atypical toxic responses in mouse bioassay