Problem Dinoflagellates in Algoa Bay
du Preez, D.
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Dinoflagellate blooms, also known as red tides, are a worldwide phenomenon. The frequency of these blooms has been increasing in recent years and large dinoflagellate blooms have been seen in areas where they have not been previously recorded or if they have, the blooms have been a minor occurrence. Foreign dinoflagellate species are being transported around the world in a variety of unnatural ways. Among these are ballast water from ships as well as with animals for aquaculture. Bloom-forming and toxic dinoflagellates can be problematic. Red tides have significant negative effects on aquaculture as well as on the indigenous organisms from the area. Algoa Bay has two harbours, one of which is a deep water port. There are also two shellfish aquaculture farms in the Bay. The hypothesis for this project was that the oyster farming in Algoa Bay had brought in foreign dinoflagellate cysts and that such cysts would have sunk into the sediment at the time of seeding. The method for the identification of dinoflagellate cysts was to use cross polarizing filters on a microscope with the addition of a lambda plate. In all the sediment sampled from all the sites for the project only one dinoflagellate cyst was found. By contrast Bay waters had an abundance of cysts. So it seems that, in this case, the oyster farming has not brought in any foreign dinoflagellate cysts which could potentially be a problem for Algoa Bay.