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

Abstract

The cyanobacterium, Aphanizomenon ovalisporum (Forti) is reported herein for the first time in Australia. Its distribution appears to be restricted to an isolated subtropical region which has distinctive water quality parameters including ready availability of nutrients and relatively high chloride and hardness levels. Blooms of A. ovalisporum in Queensland, Australia, formed a thick brown surface scum from spring to autumn in newly constructed shallow lakes. During such blooms, the water and cellular material were both found to contain cylindrospermopsin, a water soluble toxin that produced fatty livers with hepatocyte necrosis in mice similar to the toxicity produced by Cylindrospermopsis raciborskii (Wolosz.). Toxin levels in freeze-dried A. ovalisporum are approximately 25% of those present in freeze-dried C. raciborskii. However, A. ovalisporum appears to release more of the produced toxin into the water body than does C. raciborskii. Sequencing of the 16s ribosomal RNA gene of A. ovalisporum isolated from the Australian bloom showed that it was virtually identical to A. ovalisporum isolated from Lake Kinneret. Much lower homology was found between A. ovalisporum 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. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 167–177, 1999