Characterisationand Determination of PSP Toxins in Neurotoxic Cyanobacteria

AndMethods for their Removal from Water

ReportNo WSAA 148

July 1998

SYNOPSIS

ParalyticShellfish Poisons (PSPs), also known as saxitoxins, are produced by somecyanobacteria (blue-green algae). Neurotoxicity of Australian species of Anabaena circinalis has been shown to bedue to these toxins. As toxic A.circinalis  blooms are a commonoccurrence in freshwater bodies throughout Australia, it was essential todevelop a sensitive method for the analysis of these toxins in scum materialand water. It was found that the methodology for the analysis of PSPs inshellfish was readily transferable to cyanobacteria, and an HPLC technique withpost-column derivatisation and fluorescence detection was evaluated and furtherdeveloped in our laboratories. A method for the extraction of these toxins fromwater, however, had not previously been reported.

Anextraction procedure utilising ion-pair chromatography on a solid phase ofgraphitised carbon black was developed and was capable of extracting GTX2,GTX3, C1, STX, and neoSTX with excellent recoveries from both high purity waterand raw water. The C1 toxin recovery was, however, low and variable (between20%-50%).

Themethod developed was used to determine the effectiveness of the oxidantschlorine, potassium permanganate and ozone for removing PSPs from water. It wasfound that the rate of oxidation of these toxins was relatively slow. With adose of 20 mg/L chlorine and despite maintaining a high level of residualthroughout the experiment, complete oxidation of the toxin took 40 minutes.Permanganate was less effective than chlorine for the removal of the toxinsand, 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) andwas found to be ineffective at this dose. However, there was essentially noresidual 30 minutes after dosing but high concentrations of the toxinsremained. A higher dose was therefore required.

Itwas determined that the rate of oxidation of STX was much greater than that forC1/2 or GTX2/3 for all the oxidants tested.

Ageographical distribution study of the occurrence of saxitoxins in Anabaena throughout Australia was undertaken.49 samples of Anabaena were collectedthroughout Australia and neurotoxicity was only found in the species A.circinalis. Of these samples, 80% werefound 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 themost abundant. The N-hydroxy PSPs were not detected in any of the field samplescollected.

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