Characterisation and Determination of PSP Toxins in Neurotoxic Cyanobacteria and Methods for their Removal from Water
This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.
Report No WSAA 148
Paralytic Shellfish Poisons (PSPs), also known as saxitoxins, are produced by some cyanobacteria (blue-green algae). Neurotoxicity of Australian species of Anabaena circinalis has been shown to be due to these toxins. As toxic A. circinalis blooms are a common occurrence in freshwater bodies throughout Australia, it was essential to develop a sensitive method for the analysis of these toxins in scum material and water. It was found that the methodology for the analysis of PSPs in shellfish was readily transferable to cyanobacteria, and an HPLC technique with post-column derivatisation and fluorescence detection was evaluated and further developed in our laboratories. A method for the extraction of these toxins from water, however, had not previously been reported.
An extraction procedure utilising ion-pair chromatography on a solid phase of graphitised carbon black was developed and was capable of extracting GTX2,GTX3, C1, STX, and neo STX with excellent recoveries from both high purity water and raw water. The C1 toxin recovery was, however, low and variable (between 20%-50%).
The method developed was used to determine the effectiveness of the oxidants chlorine, potassium permanganate and ozone for removing PSPs from water. It was found that the rate of oxidation of these toxins was relatively slow. With a dose of 20 mg/L chlorine and despite maintaining a high level of residual throughout the experiment, complete oxidation of the toxin took 40 minutes. Permanganate was less effective than chlorine for the removal of the toxins and, in terms of a water treatment technique for the removal of these toxins, can be considered ineffective. Ozone was dosed at 2mg/L (dissolved ozone) and was found to be ineffective at this dose. However, there was essentially no residual 30 minutes after dosing but high concentrations of the toxins remained. A higher dose was therefore required.
It was determined that the rate of oxidation of STX was much greater than that forC1/2 or GTX2/3 for all the oxidants tested.
A geographical distribution study of the occurrence of saxitoxins in Anabaena throughout Australia was undertaken.49 samples of Anabaena were collected throughout Australia and neurotoxicity was only found in the species A. circinalis. Of these samples, 80% were found to contain PSPs. The typical toxin profile of a neurotoxic strain was C1,C2, GTX2, GTX3, dcGTC2, dcGTX3, and STX, with the C toxins C1 and C2 being the most abundant. The N-hydroxy PSPs were not detected in any of the field samples collected.