Posted by: Saving Water SA (Cape Town, South Africa) – partnered with Water Rhapsody conservation systems – 16 December 2010
In 1997 there was a catastrophic poisoning of the Wildevoelvlei, one of the Noordhoek Valley Wetlands. A highly toxic blue-green bloom formed on the surface of the lakes as a result of wastewater overflowing from water treatment works. The treated and untreated water had a high concentration of phosphates – a major component of washing powder. SANParks eventually turned the lake anoxic, thereby killing an entire generation of organisms.
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The City of Cape Town asked the public on Wednesday [15 Dec 2010] to avoid the Wildevoelvlei in Noordhoek Valley because of a toxic blue-green algae.
“Wildevoelvlei has a well-established algal population, dominated by species of blue-green algae (Cyanophyceae),” the city said.
“This algal group has the ability, under certain conditions, to produce toxins which can be harmful to humans and animals if ingested.”
It said people were advised to avoid contact with the water in the outlet channel leading to the sea.
Exposure to the algae could cause eye irritation, skin rashes, mouth ulcers, vomiting, diarrhoea, and cold or flu-like symptoms.
It had been established that the vlei had an outbreak which affected water flowing downstream and discharging on a section of Noordhoek Beach.
The city said dog-walkers should ensure that their pets remain on their leashes so that they were not able to drink the water.
Harvesting, sale and consumption of shellfish from the rocky outcrops near the outlet to the sea – Klein Slangkop on Noordhoek Beach – was also not advised.
Shellfish such as mussels harvested from this area were likely to be unfit for human consumption as a result of the toxins, it said.
Any person that came into direct contact with the blue-green algae, had to wash themselves immediately with clean water. If any symptoms were present, they had to immediately seek medical advice.
The city’s environmental health officials were in the process of erecting additional signs at various locations to warn the public of the situation.
It said it would continue to monitor the water quality and keep the public informed.