Red tide fear in Bay after ‘sightings’
Unlike Knysna, no warning of danger issued
WARNINGS against fishing for shellfish in the Knysna area have been issued due to fears of possible red tide, while there have also been claims of sightings off Nelson Mandela Bay.
Despite the reports of sightings off the Algoa Bay coastline, no warnings have been issued for the area as yet, according to Department of Economic Development, Environmental Affairs and Tourism (DEDEAT) spokesman Sixolile Makaula.
“As far as we know it has been confined to the Knysna area. We have not yet received information of it along Algoa Bay. If there have been sightings these have not been confirmed,” he said.
This comes after warnings of a possible red tide approaching Knysna were issued when water samples collected from two key points in the town's estuary confirmed the presence of phytoplankton in the water.
As a result, SANParks, the Knysna Municipality and the Knysna Basin Project warned the public against fishing for shellfish until further notice.
Although the relatively low numbers of phytoplankton were unlikely to cause a bloom, Garden Route National Park senior section ranger Owen Govender said other blooms could be stored in mussels until they became poisonous and presented a danger to humans if eaten.
“It is for this reason that we are cautioning against fishing for mussels in the estuary until it is safe to do so,” he said.
Red tide is caused when microscopic phytoplankton, usually of a type called dinoflagellates, lift to the water surface where the ideal conditions of temperature and light trigger their germination. This gives the water a reddish or brown coloration.
Paralytic shellfish poisoning, which produces toxins that disrupt normal nerve functions, can be associated closely with dinoflagellates, and symptoms appear between one and five hours after eating contaminated seafood.
Symptoms include nausea, vomiting, diarrhoea, abdominal pain and tingling or burning lips, gums, tongue, face, legs and toes.
Red tide starves fish of oxygen, and can have a devastating impact on marine life populations.
In 2002 tens of thousands of crayfish beached themselves at Elands Bay on the West Coast, forcing the Western Cape government to relocate the shellfish.
A more dire situation occurred at Elands Bay in 1997, when about 1 500 tons of beached crayfish were crushed to death in the stampede of people who tried to collect as many as possible.
Rob Mac Geoghegan, who runs volunteer organisation Search and Rescue Eastern Cape, said he had spotted red tide off the Algoa Bay coastline on two separate occasions in the past two weeks.
“Last Monday I saw patches of red tide between Seaview and Jeffreys Bay and then yesterday [Tuesday] I saw it just off Cape Recife. It was about 600m to 800m from the shoreline and it covered about 50% of the sea. I have not heard of any warnings being issued and I am not sure people ac- tually know that it is out there.”
Mac Geoghegan said he believed recent weather conditions made it difficult to spot the red tide because cloud cover caused dark shadows over the ocean.
But Wildlife and Environmental Society of SA (Wessa) senior conservation officer Morgan Griffiths said he was not aware of any sightings of red tide along the coastline, but had heard of the Knysna warning.
“It is probable but it will only cause problems if the wind blows it closer towards shore and creates a walk-out [of marine life].”
Griffiths said red tides in the area tended to be small and isolated. “However things could change. If people find fish or shellfish ashore they should exercise extreme caution because they may be poisonous.”
Dr Malcolm Smale of Bayworld and Craig Lambinon of the National Sea Rescue Institute also said they were not aware of any red tide occurring along the Nelson Mandela Bay coastline.
Municipal spokesman Mthubanzi Mniki said officials were aware of the warning in Knysna.
“It cannot be linked or taught that when it happens in Knysna it might also happen on the Nelson Mandela Bay coastline. However we are continuously monitoring our coastline and there has been no indication of such until now.”
Mniki said that in the case of red tide occurring off Nelson Mandela Bay, the municipality would put signage up and place personnel throughout the affected areas as well as put out warnings to people not to consume fish that had been washed out of the sea. The fish would be tested.
In Knysna, local surfer Mark Taylor wrote on the Love Knysna Facebook page that the “red tide was blooming at Buffalo Bay” as far back as New Year’s Day.
“We . . . surfed in a weird, brown type of sea . . . tasted like iron or money.”