The City of Cape Town has denied allegations of a sewage spill in the ocean near Sunrise Circle in Muizenberg.
Marina Da Gama resident Melanie Stuart told the Echo on Thursday April 18 that she had seen a spill, describing “yellowish, brownish” water and the distinct smell of sewage.
However, mayoral committee member for water and waste Xanthea Limberg says what Ms Stuart saw wasn’t sewage.
The City’s sanitation department had found no evidence of a sewage spill when inspecting the stretch of beach from Sunrise Circle to Strandfontein Pavilion last week, she said.
The brown water was caused by algae and the tides, not sewage, she said, and it happened often along the beaches between Macassar and Muizenberg.
“Most people confuse the brown colour of the water for sewage pollution. The discolouration is caused by a naturally occurring diatom or micro-algae called anaulus australis,” she said.
Anaulus australis are sometimes called surf-zone diatoms. Surf-zone diatoms favour sandy beaches and are known in most areas of the world.
In South Africa, surf-zone diatoms are found in Algoa Bay, False Bay and the Cape South Coast.
Ms Stuart is unconvinced. She said there was definitely human excrement floating in the water.
She said that when she had visited the area again on Tuesday last week, she had still smelt sewage and there had been a more than 1km-wide stretch of discoloured ocean.The ward councillor had also tried to convince her it was algae, she said.
“I told her it was not algae and not an acceptable excuse.”
Ms Stuart said it was the worst kind of pollution and the matter needed to be prioritised by the City.
But Shark Spotters CEO Sarah Waries agrees with the City and said the water was usually changed by a surf diatom after strong south-easter winds that pushed warmer water inshore.
Contrary to popular belief, she said, a sewage spill was unlikely to cause the water to turn brown, especially not on the scale that could be seen with the diatom blooms.
She said it was regularly seen along the coast, particularly the northern shore of False Bay.
This, she said, was different from a red tide that most people thought of.
Both both red tides and the brown water in the surf zone were caused by blooms of plankton, albeit different species.
“Interestingly, we have both red tide and diatom blooms at Muizenberg at the moment,” she said.
She added that she had no knowledge of a sewage spill at that time described by Ms Stuart.