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Algal blooms

Certain algal blooms are known to produce potent toxins. Currently, six distinct human clinical syndromes associated with harmful algal blooms are recognized: ciguatera fish poisoning, paralytic shellfish poisoning, neurotoxic shellfish poisoning, diarrhetic shellfish poisoning, amnesic shellfish poisoning, and Pfiesteria associated syndrome. There is also accumulating evidence to suggest that chronic sublethal exposure to these toxins can cause long-term behaviour alteration, susceptibility to cancers and impaired reproduction for both fish and humans. At the recent ninth international conference on harmful algal blooms held in Tasmania, evidence was presented that demonstrated harmful algal blooms are both an international phenomenon and that their numbers are increasing. It was speculated that this increase is a consequence of human activity such as disruption of ecosystems, nutrient enrichment of waterways, and climatic change.

The economic impact of these harmful algal blooms was highlighted in the conference by the numerous accounts of closures of both shellfish and aquaculture farms until these blooms could be brought under control. It was also highlighted that considerable international effort is being made to monitor the levels of these toxins in both local and imported seafood produce. Indeed, several instances of trade embargoes of shellfish were noted because of high levels of algal toxins. There was an emphasis placed on a growing requirement to undertake regular testing for these toxins in marine produce and shellfish in particular. In this respect, considerable effort is being devoted to developing rapid testing procedures based on a dip-stick approach for the more common algal toxins.

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Prepared by Keith Richardson and Beverley George
Food Science Australia
PO Box 52, North Ryde 1670. Tel +61 2 9490 8397 Fax +61 2 9490 8499
Email enquiries@csiro.au