It has happened nearly every summer since 1997.

As temperatures soar across the peninsula, so too do the levels of Cyanophyceae in the Wildevoelvlei lake.

Forming an integral part of the wetland system in the Noordhoek Valley, Wildevoelvlei was once seasonal, drying out over the summer months.

But then, instead of water levels being regulated naturally by rainfall, groundwater seepage, stormwater run-off and spring tides, humans got involved.

Back in 1977 the Wastewater Treatment Works (WWTW) was commissioned, and the vlei became a permanent water body due to the treated effluent being discharged into it, explains Saving Water:

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.

The Wildevoelvlei was left with a well-established algal population, dominated by species of the blue-green algae, Cyanophyceae, which, under certain conditions, “has the ability to produce toxins which can be harmful to humans and animals if ingested”.

You see the red pin-pointer? That’s Wildevoelvlei, just above Imhoff’s Gift in the picture below. But my question to you is what is Outside? Why is it called Outside?

Okay, let’s carry on.

Once again, the levels of Cyanophyceae have risen to dangerous, and the City has warned everyone to avoid contact, reports IOL:

“The public is urged to avoid all contact with the water at the vlei and in the outlet channel leading to the sea and discharging on a section of Noordhoek Beach,” the City’s acting mayoral committee member for Area South Suzette Little said.

“Dog-walkers should ensure that their pets remain on a leash and prevent them from drinking the water.”

The harvesting, sale and consumption of shellfish from the rocky outcrops near the outlet to the sea (Klein Slangkop on Noordhoek Beach) is not advised. Shellfish, such as mussels, harvested from this area are likely to be unfit for human consumption as a result of the toxins.

Exposure to the algae could cause eye irritation, skin rashes, mouth ulcers, vomiting, diarrhoea, and cold or flu-like symptoms – and drinking the water is a big no-no.

Easily identifiable, when the algae blooms you can see green, blue-green, white or brown foam, scum or mats floating on the surface of the water.

Be careful out there. Between the deathly algae and life-threatening stabbings  on the beach, things are getting real.

[source:iol]