Gauteng and NW Province

Red tide degraded – it is now safe to use water

10th February 2014

Scientists (Knysna Basin Project and Department of Agriculture, Forestry and Fisheries) have found no evidence of toxicity of the red tide in Knysna. Of the three types of organisms that could have potentially caused the red tide in Knysna, the dinoflagellate group was identified as dominant.

Fish kills and the death of other marine life last week were due to the unusually rapid fall in dissolved oxygen (DO) in the water column. When any portion of such a large bloom collapses, this can be expected.

The red tide appears to be greatly reduced in Knysna although still evident in Tsitsikamma and surrounds, authorities (SANParks, Knysna Municipality and the Knysna Basin Project) have had no incidents of human illness reported to them as a result of the red tide.

Restaurants were delighted to receive news that the water in the estuary is now safe to use for the storage of filter feeders (mussels and oysters).

Professor Brian Allanson of the Knysna Basin Project says extensive research should continue but partners would have to think about costs associated with such a project.

What are these phytoplankton organisms?

Phytoplankton are microscopic, single-celled organisms that float in the sea, according to a Marine and Coastal Management Guideline from the Department of Environmental Affairs.  They are able to photosynthesise and form the basis of food chains in the oceans. There are three types of red tide organisms, dinoflagellates, diatoms and ciliates. Dinoflagellates usually lie dormant on the seabed until they are lifted to the surface during upwelling where the ideal conditions of temperature and light trigger their germination.

Issued by:
South African National Parks (SANParks) Garden Route Communications


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