Harmful algal blooms are not a problem for just the U.S., they occur all around the world. Another location impacted by various types of blooms is South Africa. They have some of the same types of HABs as the U.S. plus others. Click here to learn about recent research collaborations to study these HABs.
There are two oceans along the coast of South Africa: the Atlantic Ocean is on the west and the Indian Ocean is on the south. Cape Agulhas, the southernmost point of Africa, is the place where the two oceans meet. The West Coast is known for its dynamic upwelling system and productive fisheries; note the high chlorophyll concentrations in the satellite image at right (>>). The Benguela current flows equatorward along this coast and wind-driven upwelling results in the net transport of surface water offshore which is replaced by cool, nutrient-rich bottom water. This introduction of nutrients into the photic zone allows phytoplankton to grow rapidly and at times results in blooms (some form huge red tides). Most of these blooms are healthy and are responsible for the productive fisheries. However, there are also recurrent harmful and toxic blooms along the coast of South Africa.
Paralytic Shellfish Poisoning (PSP)
  • Organisms impacted by PSP in this area include white and black mussels, anchovy, herring, mackerel, and sardine. Toxins may also be transferred through the food web to whales and seals. In March 1980, approximately 5 million white mussels were washed ashore at Elands Bay after becoming toxic from an Alexandrium catenella bloom.
  • An interesting feature about PSP in South Africa is that their abalone industry is being threatened. This is perplexing because abalone are not known to be filter feeders and do not graze microalgal cells. Instead they feed on kelp. Research is underway to determine how the abalone are picking up the PSP toxins. One thing that is known is once the abalone acquire the toxins, they do not get rid of them quickly. It may take up to a year for abalone to be eaten safely. This ability to retain toxins is similar to the butter clam found off of Alaska's coast.
Diarrhetic Shellfish Poisoning (DSP)
Neurotoxic Shellfish Poisoning (NSP)
  • The dinoflagellate Gymnodinium cf. mikimotoi is present on the southern coast of South Africa and blooms frequently in False Bay. This species causes NSP symptoms similar to those reported during Gymnodinium breve blooms off the Florida coast.
  • Problems associated with these blooms include skin and respiratory irritations.
  • In 1989, 30 tons of abalone were killed on the South Coast after a G. mikimotoi bloom.
Amnesic Shellfish Poisoning (ASP)
  • This illness has not yet been reported in South Africa
  • However, the diatom responsible for ASP in other regions, Pseudo-nitzschia sp., is present along certain areas of the coast (see microscope image at right, >>).
HARMFUL (non-toxic) BLOOMS
Brown Tides
Hydrogen Sulfide Poisoning
  • In March 1994, St. Helena Bay on South Africa’s West Coast experienced a massive marine mortality.
  • The event was caused by the decay of a huge red tide of non-toxic dinoflagellates (dominated by Ceratium furca and Prorocentrum micans).
  • About 60 tons of rock lobster and 1500 tons of fish were washed ashore.
  • The lobster and fish died from suffocation and hydrogen sulfide poisoning. Oxygen concentrations were near zero and hydrogen sulfide concentrations were in excess of 50 micromols per liter!
  • In 1997 there was a massive bloom of the dinoflagellate Ceratium furca in Elands Bay on the West Coast.
  • When the bloom decayed, bacterial consumption drastically reduced oxygen levels. Oxygen concentrations were so low that over 1500 tons of rock lobster became stranded on the beach and died.
  • Anoxic events may lead to hydrogen sulfide poisoning as the bacteria begin to use sulfur when oxygen isn’t available.
Red and Black Tides
  • Red tides are common along the South African Coast and are caused by a variety of species. Some are harmful or toxic, while others are not.
    • Noctiluca scintillans is one of the many species in this region to form red tides. This species is not toxic; however, it may cause fish mortalities when blooms decay producing high ammonia levels.
    • Mesodinium rubrum, a photosynthetic ciliate, also discolors the water and appears purple or wine colored. It is not toxic, although it has been associated with faunal mortalities during bloom decay in St. Helena Bay (described above). This species is one that performs diel (i.e., daily) vertical migration making the red tide apparent only during certain parts of the day.
    • Diel vertical migration is a behavior characteristic of algae that have the capability to swim (e.g., dinoflagellates). They spend part of their time in the surface waters, photosynthesizing where light is available. At night, these organisms can swim down toward higher nutrient concentrations. This behavior can determine whether or not a red tide is visible.
      • Ciliates may form a bloom below the surface waters even though the water color doesn’t appear red. As the ciliates swim back to the surface in the middle of the day, the red tide can re-appear.
  • Black tides were observed in St. Helena Bay during the hydrogen sulfide poisoning event in 1994 (described above). In this case, all of the light entering the ocean was absorbed by the particles and dissolved material in the water associated with the bloom.
Fish Kills: Chaetoceros- or Heterosigma-related
  • Although species of Chaetoceros and Heterosigma are present in South African waters, there have been no reported fish kills associated with these blooms.
Freshwater blooms