- About 500 tons of West Coast rock lobster walked out of the sea and died.
- This is due to the harmful algal bloom known as red tide.
- The lobsters and other fish that died may be poisonous and should not be eaten.
The SA National Defence Force (SANDF) and police are helping with the clean-up of an estimated 500 tons of West Coast rock lobster which walked out of the sea to escape the harmful algal bloom known as red tide.
The Department of Forestry, Fisheries and the Environment said the lobster walkout was due to the usual build-up of blooms of phytoplankton in the greater St Helena Bay region over the past weeks.
The build-up is typical for summer but the current build-up extends to between 50 and 60km, affecting waters in the vicinity of Elands, Lambert's, and Doring bays.
The lobster walkout is to escape oxygen depletion.
On Monday, the department said a red alert had been activated and was supported by the West Coast District Municipality, Cederberg Municipality, police, SANDF, Western Cape government and local communities.
The plan is to recover the lobsters that are still alive so they can be rehabilitated and returned to the sea once the red tide threat has diminished.
However, the public has been advised not to collect and consume any of the dead lobster, fish and shellfish washed ashore because they may contain dangerous toxins.
What is red tide?
Algal blooms are the tiny organisms seen at the top of water in the sea or lakes.
In this case, they are dominated by a group of phytoplankton known as dinoflagellates, and are an important part of the food chain.
However, when there are too many of them in one place inshore, particularly during periods of calm, they die, or cause a drop in oxygen levels in that part of the sea.
The low oxygen conditions cause the death of marine life. Such mortalities were observed on the beaches of Elands Bay earlier on Wednesday.
With the prediction of light westerly winds over the next few days, the risk of further mortalities is high.
Some dinoflagellates can produce toxins that are also harmful to humans. These toxins may accumulate in shellfish also affected by the red tide.
The department said poisoning might either take place through the consumption of seafood that was contaminated by toxic algae, toxic aerosols or water-bound compounds that caused respiratory and skin irritation.
Fisheries and aquaculture industries suffer from the death of marine stocks caused by red tides, while poor water quality and foul smells associated with these occurrences affect coastal tourism.
Red tides are particularly common in the West Coast's upwelling regions, such as the Benguela, California, Humboldt, Canary, and Somali upwelling systems.
Upwelling is when cold water moves to the surface and it takes fresh nutrients to species which live there.
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