Non-toxic green algae in Milnerton Lagoon water
14 March 2022
The City of Cape Town can confirm that the algae currently present in the Milnerton Lagoon is non-toxic green algae.
The City’s Water and Sanitation Directorate is still investigating the possible source(s) of this algal bloom.
The City will continue to monitor the lagoon’s water quality and will assess whether mechanically opening the estuary mouth will assist.
‘The Water and Sanitation Directorate investigated the water quality of the Milnerton Lagoon, and we have created a list of possible pollution sources for the catchment. The directorate is closely monitoring all pollution sources and does regular water quality sampling and physical inspections of our infrastructure. The Bulk Infrastructure Department confirms that Potsdam WWTW is a small contributor to the problems we face with the waterway. The treatment facility achieves high compliance ratings for its treated effluent which sometimes has nutrients present in the discharge. At no point has Potsdam WWTW discharged raw effluent or had any emergency or unauthorised discharges that could have resulted in the algae bloom,’ said the City’s Mayoral Committee Member for Water and Sanitation, Councillor Zahid Badroodien.
The City’s Scientific Services are routinely monitoring the Diep River and the lagoon.
Although there are no blue-green algae present in the lagoon, harmful algal blooms are an ongoing threat, particularly in the vleis and water bodies (including Milnerton Lagoon) which are in nutrient rich situations and are exposed to hot weather.
The concentration of algae can vary due to factors that can influence their growth through a range of possible sources.
As a precautionary approach, the City has installed additional warning signs over the weekend to remind residents that the Milnerton Lagoon is closed to the public. The Milnerton Lagoon is not suitable for recreational use and signage to inform the public as such has been in place at the lagoon for several years now.
The City’s Biodiversity Management Branch will continuously monitor the lagoon to see if there is any impact on wildlife and fish.
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Published by:
City of Cape Town, Media Office
