Algal bloom closes waterway

THE City of Cape Town has closed the Rietvlei waterway after a hazardous algal bloom appeared on Thursday, which led to the Milnerton Aquatic Club cancelling its 24- hour endurance sailing challenge.

Julia Wood, City manager of biodiversity management, environmental resource management, said the decision was made yesterday after having analysed the water for two days.

Accumulative microcystin toxins, which exceeded the World Health Organisation’s guidelines, had been found.

Wood said this was the second time this had happened in the past 11 years at Rietvlei.

She said blue-green algae was dangerous and could cause nausea and rashes.

“The water quality of Rietvlei has largely always been very good, but the rain may have washed some nutrients out of it,” said Wood.

The Milnerton Aquatic Club refused to comment on the cancellation of the challenge which would have ended tomorrow.

“It is suspected that the 5mm rainfall that was recorded on Wednesday washed accumulated minerals and organic material from decomposing and dead plants along the shoreline into the water at Rietvlei,” Wood said.

“These minerals and organic materials, combined with high ambient temperatures, could have provided the nutrients for the rapid growth of algae in the water.”

The City has urged people to avoid all contact with the water at Rietvlei until it is declared safe.

They said while the fishing area was closed, the public could still access the Table Bay Nature Reserve’s other facilities such as the picnic areas and the bird-watching trail.