Geographical patterns of occurrence and composition of saxitoxins in the cyanobacterial genus Anabaena (Nostocales, Cyanophyta) in Australia

Cyanobacterial samples were collected between April 1989 and May 1997 from six drainage divisions in coastal areas of Australia: the northeast coast, southeast coast, Tasmania, Murray-Darling Basin, South Australian coast and southwest coast. Saxitoxins were detected in approximately 70% of all fiel d samples and 57% of cultured strains of Anabaena circinalis. Maximum saxit oxin concentrations were 4466 and 2553 mug g(-1) dry weight cells in field samples and strains, respectively. Toxin profiles were similar in the major ity of field samples and strains. The toxins were predominantly C-toxins (C 1 and C2) and gonyautoxins (GTX2 and GTX3), with saxitoxin sensu stricto (S TX). GTX5 and decarbamoyl gonyautoxins (dcGTX2 and dcGTX3) being present in minor amounts, A unique toxin composition (exclusively STX and GTX5) was F ound in a geographically isolated strain from the southwest coast of Austra lia. N1-hydroxy saxitoxins (neoSTX, GTX1 and GTX4) were not detected in any field sample or cultured strain. Anabaena circinalis may not be the only A nabaena species producing saxitoxins, as very low concentrations of GTX3 (1 4 mug g(-1) dry weight cells or less) were detected in two other Anabaena s pecies: A. perturbata var. tumida and A. spiroides. One decarbamoyl gonyaut oxin (dcGTX3) was also present in one A. perturbata var. tumida strain. Ana toxin-a was not detected in Australian strains of Anabaena. Trace amounts o f 0.23 and 0.10 mug microcystin-LR equivalents g(-1) dry weight cells were found in two cultured strains of Anabaena cylindrica. An increase in toxin concentration from 0 to 4423 mug saxitoxins gl dry weight cells was observe d over a 3-month period in a series of samples collected from a persistent bloom of A. circinalis at Wongulla Lagoon. South Australia. This temporal v ariation in saxitoxin concentrations is similar to that reported for microc ystins in Microcystis aeruginosa (Chroococcales, Cyanophyta).