Blooms of the cylindrospermopsin containing cyanobacterium, Aphanizomenon ovalisporum (Forti), in newly constructed lakes, Queensland, Australia

The cyanobacterium, Aphanizomenon ovalisporum (Forti) is reported herein fo r the first time in Australia. Its distribution appears to be restricted to an isolated subtropical region which has distinctive water quality paramet ers including ready availability of nutrients and relatively high chloride and hardness levels. Blooms of A. ovalisporum in Queensland, Australia, for med a thick brown surface scum from spring to autumn in newly constructed s hallow lakes. During such blooms, the water and cellular material were both found to contain cylindrospermopsin, a water soluble toxin that produced f atty livers with hepatocyte necrosis in mice similar to the toxicity produc ed by Cylindrospermopsis raciborskii (Wolosz.). Toxin levels in freeze-drie d A. ovalisporum are approximately 25% of those present in freeze-dried C. raciborskii. However, A. ovalisporum appears to release more of the produce d toxin into the water body than does C. raciborskii. Sequencing of the 16s ribosomal RNA gene of A. ovalisporum isolated from th e Australian bloom showed that it was virtually identical to A. ovalisporum isolated from Lake Kinneret. Much lower homology was found between A. oval isporum and other species of that genus (i.e., A. flos-aquae and A. gracile ) or C. raciborskii, which is known to produce the toxin cylindrospermopsin . (C) 1999 by John Wiley & Sons, Inc.