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Harmful Algal Bloom (Red Tide) outbreak in the Garden Route Coastal areas

15 December 2015


The Department of Environmental Affairs (DEA) can confirm that there is still Harmful Algal Bloom (HAB) also known as Red Tide, outbreak in some parts of the Garden route coastal area, affecting areas such as Plettenberg Bay, Knysna and Wilderness.

The bloom is normally caused by microscopic organisms that are found in the sea water and are able to photosynthesise. The characteristics of which is a redish brown colour of the water seen mostly on the sea surface. Three types of the microscopic organisms are Dinoflagellates, Diatoms and Ciliates which can be lifted to the surface during upwelling. This was first seen on Monday (07 December 2015) and the concentration has been constant since then. The bays are also visibly affected and some of these are areas where communities swim and fish.

The DEA is in touch with the Department of Agriculture Forestry and Fisheries (DAFF) as there is also fishing activities permitted in this area. The HAB is expected to last for the next couple of days to a few weeks, as that is usually the case for HABs. Unfortunately nothing can be done about it as it is part of a natural process, however the expectation is that nature will take its course and the HAB will subside with time.

At this stage no wash ups and walk outs have been observed although the HAB can be toxic in nature. Toxicity of the HAB may lead to a large number of fish, like Crayfish, Shellfish, Linefish species and other marine organisms dying. This may also be as a result of low oxygen levels in the sea water from the death of phytoplankton.

The public is discouraged from fishing, bathing or swimming in an area of the outbreak until the condition is reported to be back to normal. Fish or marine organisms from the area may not be caught or consumed as the bloom could be toxic and may lead to death by Paralytic Shellfish Poisoning (PSP). Dinoflagellates are known to cause PSP, a toxin that can attack the nerve functioning in humans. There are and will continue to be talks between DEA, DAFF, Cape Nature, South African National Parks, South African Environmental Observation Network (SAON), Universities (NMMU) and other relevant and interested parties including the communities to deal with the situation.


HABs are natural phenomena in coastal waters caused by a dense accumulation of microscopic algae. These minute organisms carry pigments to photosynthesize which give HABs their typical reddish-brown appearance. HABs occur in most coastal regions of the world, and are particularly common in the productive west coast upwelling regions, such as the California, Humboldt, Canary, Somali and Benguela upwelling systems. 

Some of the 29 algal species that are known worldwide for forming HABs are harmful because they contain toxins, which are poisonous to humans. Poisoning may either take place through the consumption of seafood that is contaminated by toxic algae, or by toxic aerosols or waterbound compounds that cause respiratory conditions and skin irritation. Other HABs cause harm through the depletion of oxygen (anoxia), which affects all marine creatures and can lead to mass mortalities of entire marine communities or mass walkouts of rock lobsters that try to escape the anoxic conditions.

Therefore HABs events can potentially have major environmental as well as societal implications, with knock-on effects on coastal economies.

For media queries contact:

Zolile Nqayi
Cell: 082 898 6483