LEVELS OF MICROCYSTIN-LR IN RAW AND TREATED WATERS
Report No FR0337
H A James, C Smith, A Sutton and S Patel
As a result of the application of the analytical method developed to determine microcystin-LR in water, it has been possible to reliably measure levels of this toxin in reservoir waters and drinking waters for the first time. Generally, even in samples containing visible algal cells, levels were below the detection limit of the method (0.2-0.3 µg l-1)
To apply the method developed for the analysis of microcystin-LR to samples of reservoir waters and drinking waters taken while blue-green algae were present in reservoirs.
Until data are available on levels of microcystin-LR in water, it is impossible to assess the significance of this toxin in relation to recreational use of reservoir waters. It is also necessary to examine reservoir derived drinking waters produced at times when significant numbers of algal cells are present in the raw water, to establish whether microcystin-LR is present, and if so, at what levels.
IV RESUME OF CONTENTS
Water samples (mainly from Scotland) submitted to WRc for analysis during the period June-October 1992 were analysed. Of the 23 samples examined, few contained detectable levels of microcystin-LR. Three related reservoir water samples contained microcystin-LR at a level (0.2 µg l-1) just above the detection limit. One sample of a senescent algal scum, which contained extremely high levels of algal cells (Microcystis sp.) was found to contain high levels (8.5 mg l-1) of microcystin-LR. However none could be detected in another similar sample from a different location, in which the algal cells were buoyant. It has been shown for one sample that although there were toxin-containing algal cells visibly present in the sample, levels of microcystin-LR in the water were undetectable.
Generally, microcystin-LR could not be detected in most of the water samples examined. However, the lysis of large numbers of algal cells can result in high levels of toxin in water in the vicinity of a decaying bloom.
As the number of samples examined was relatively low, additional samples need to be analysed to confirm the findings reported, and to establish whether the conclusions are generally valid. When a suitable method is available, such water samples (particularly those associated with Anabaena blooms) should also be analysed for the neurotoxin, anatoxin-a.
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