Black water algal bloom stretching up to Perseverance

Drone footage has revealed further expanses of the Swartkops Estuary is covered in the harmful exotic black algal bloom Heterosigma akashiwo.

Scientists have warned that the “black water event” is bad news for biodiversity, fish stocks and possibly human health too and are calling for the authorities to be held accountable.

The aerial footage from the Zwartkops Conservancy shows large tracts of the estuary above Redhouse as coal-black in colour with a brown scum floating on the surface.

Zwartkops Conservancy spokesperson Jenny Rump said she and her team were aiming to check the situation above Perseverance yesterday.

“We know from our drone footage so far that the bloom extends from Redhouse upriver through Sumcay and to Perseverence.

“So we’re headed to above that point today.

“We’ll be observing and checking for any evidence that there has been a die-off of invertebrates like mud prawns.

“We know a lot of birds have been feeding on the banks where they don’t normally feed so we think that might be the reason.”

They would also be taking samples of the water for testing, she said.

“We’ll be taking the samples to Talbot’s [laboratory in Cape Road] asking for them to check for ecoli and nutrients.

“The outflow from the treatment plants is clearly fuelling the algal bloom so the results will likely support this but we want to get an idea of the levels.

“We’ll also be checking on how the water treatment plants in Uitenhage and Despatch are functioning at the moment.”

NMU estuarine ecologist Prof Janine Adams said on Monday that the bloom of Heterosigma akashiwo was a first for Swartkops and was due to the accumulation of nutrients in the estuary after years of sewage spills from the overloaded Despatch, Kelvin Jones and KwaNobuhle waste water treatment plants.

The nutrients had also accumulated because treatment standards were not high enough even when the plants were functioning, she said.

NMU researcher Dr Daniel Lemley, who did his doctorate on Heterosigma akashiwo — which originated from Japan and came to South African shores via ship’s ballast water or migratory birds — said yesterday the high levels of phospherous and nitrogen being allowed into the system were the problem.

“Even when the plants are complying with the legislation, these levels are far to high for the effluent to be released into an estuary.”

The algae was not considered toxic but should be avoided, he said.

“It contains a slimy mucus and I would not recommend you swim in it.”

Adams said this mucus could get caught in the gills of fish and kill them.

NMU fish specialist Prof Nadine Strydom said Heterosigma’s boom-bust life cycle — saturating the water with oxygen when it bloomed and leaching oxygen when it decayed — also negatively affected various species.

Young fish and other estuarine creatures which could not take evasive action might either not develop properly or die.

Strydom said dire management of the vital service of water treatment was the root of the problem.

“If it is being managed so badly as we see here — what does this say about the management of our drinking water?

“We need to hold our authorities accountable.”

Questions were e-mailed to metro spokesperson Mthubanzi Mniki on Monday, and receipt was confirmed, but despite several follow-ups, no response was available by the time of going to print.

Efforts were also made to call and text municipal health boss Dr Patrick Nodwela, but he could not be reached.