RED TIDES ( Archived) (5)

Toxins produced by certain dinoflagellates are some of the most potent poisons known to man. The most notorious of the dinoflagellate toxins are the neurotoxins which disrupt normal nerve functions. Toxins of this nature have caused numerous marine mortalities on the South African coast. Virtually the entire adult mussel population in the Elands Bay area was destroyed by the dinoflagellate Gonyaulax catenella in 1980, while 30 tons of abalone were washed up in the HF Verwoerd Marine Reserve in 1989, following blooms of the dinoflagellate Gymnodinium nagasakiense, a recognized fish killer in the coastal waters of Japan.
In recent years there has been a growing awareness worldwide of the problems associated with red tides, largely due to the expansion of the shellfish industry and the increased risk to human health. In addition, scientists have concluded that red tides are occurring with increasing intensity and frequency over a wider global distribution, and that this may be a result of human activities. Nutrient enrichment through various forms of pollution, and subtle changes ascribed to the greenhouse effect, are thought to have influenced the intensity and frequency of red tides. Also, the transport of dormant cycts in the ballast tanks of ships is thought to have contributed to the spreading distribution of red tide outbreaks. It has therefore been recommended that an international research effort be undertaken to evaluate the global expansion of algal blooms and man's involvement in it.
The aim of this research includes finding a way of accurately predicting red tide outbreaks, so ensuring that steps can be taken to warn the public in advance. Simple predictive models have been developed for certain dinoflagellate species, but these can only be applied to specific areas. Good monitoring programmes are therefore still the most satisfactory means of providing an efficient warning system.
In South Africa the responsibility for monitoring red tide rests with the Chief Directorate Sea Fisheries of the Department of Environment Affairs. Researchers from the Sea Fisheries Research Institute (SFRI) regularly monitor the waters around our coast for red tide outbreaks in order to warn the public of potentially harmful blooms. Members of the public should notify the SFRI at 021-4396160 of unusual discolourations of the sea or illness following the consumption of shellfish. The Red Tide Hotline (021-4394380) is a 24-hour answering service that provides information concerning outbreaks of red tide detected by the SFRI.