Toxic Cyanobacteria in Water Supplies: Analytical Techniques

This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.

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Report No UWRAA 26

May 1991

SYNOPSIS

This project, jointly funded by the Urban Water Research Association of Australia and the South Australian Engineering and Water Supply Department, was undertaken for the purpose of identifying toxic algae present in water supplies and determining their public health significance. Five discrete aims were identified, viz,

To develop methods for the quantitative determination of toxins produced by algae
To develop methods for the identification of toxic strains of algae
To investigate conditions which promote toxin production
To determine the spatial and temporal distribution of toxins in algal blooms
To assess the public health significance of toxin production

The principal findings of the research carried out are:

Peptidehepatotoxins can be readily separated in extracts of scum samples by high performance liquid chromatography (HPLC) using isocratic elution with anacetonitrile/ phosphate buffer mobile phase and UV detection at 240 nm. These toxins are readily extracted using butanol/ methanol/ water with high precision.

Toxins can be isolated using preparative HPLC and in most cases identified using fast atom bombardment (FAB) mass spectrometry.

Microcystins were identified in scum samples from a number of geographically separated locations. Although concentrations varied considerably at some locations overtime, the same compounds were always present. At other locations different microcystins were present at different times. Because of the manner of sampling it is not known whether these findings were due to spatial variation within the bloom, to temporal variation or to a combination of both.

Nodularin was identified in toxic samples of Nodularia spumigena from Lake Alexandrina, SA.
There are a number of microcystins formed by Australian species of Microcystis aeruginosa with up to six possibly occurring in any one sample.
Samples which are “non-toxic” by mouse bioassay may still contain low levels of microcystins.

Within the time available it was not possible to address all aims fully. In particular, methods for identifying toxic strains of algae were not investigated. It was intended to develop allozyme electrophoresis as a method for identifying toxic strains and compare results with conventional morphological taxonomy. In addition, only limited investigations of conditions affecting toxin production, and of the spatial and temporal distribution of toxins in blooms were carried out. The results of these investigations will be presented in a separate UWRAA report at a later date. Finally the overall findings of the investigation were inadequate to allow the issue of the public health significance of toxins to be addressed. The investigation also centred on the peptide toxins produced by cyanobacteria. Neurotoxins produced by other cyanobacteria, especially species of Anabaena, were not studied.

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