Black algae containing the cyanobacteria Okeania spp on Blackpool Beach, Waiheke Island in December.
Black algae containing the cyanobacteria Okeania spp on Blackpool Beach, Waiheke Island in December.
Black algae has washed up at a new beach after a “perfect combination” of conditions led to the stinky substance taking over some spots in the Hauraki Gulf.
And hot weather could make the smelly organisms more frequent disturbances for local beach-goers.
The Auckland Regional Public Health Service has saidthe algal bloom could lead to skin, eye and respiratory irritations.
“This year, the quantities appear to be higher than last year,” said Craig Mcilroy, general manager of Auckland Council’s Healthy Waters.
“We have removed 400 tonnes so far and have approximately 150 tonnes to go. Last year we removed approximately 400 tonnes of algae.”
Mcilroy said that algae was removed from two beaches on Waiheke Island.
“Last year we removed algae from a third beach on Waiheke, Shelley Beach. However, the algae has not returned here in significant quantities this year.”
He said the black algae had also washed up at Kawakawa Bay in East Auckland this month.
Mcilroy said Auckland Council sent samples for testing to confirm if Okeania spp and the toxin Lyngbyatoxin-A were present in the Kawakawa Bay sludge.
He told the Herald it was hard to predict where cyanobacterial blooms would occur.
Trying to pick the size and duration of these blooms was also a guessing game.
“This is because numerous environmental conditions need to be met to enable the rapid growth of the cyanobacteria - calm weather conditions, plenty of light, warm seawater temperatures and sufficient nutrients to sustain their growth,” he added.
In the 1970s, the algal bloom dominated Motukaraka Island in Beachlands. Photo / Sky View Photography
Warm sea temperatures were also a factor.
“These requirements mean blooms most commonly occur during spring and summer, and are a natural phenomenon in shallow, productive coasts,” Mcilroy said.
“It is likely that a perfect combination of conditions in recent months has resulted in the current washed-up bloom on Waiheke Island.”
It forms into slimy, dark-coloured mats on the beach.
NZ Food Safety still had a shellfish biotoxin warning in place this week for Okeania spp around Blackpool and Surfdale Beaches.
It said the algae could produce Lyngbyatoxins, causing respiratory illness and skin rashes.
It said cooking shellfish would not remove the toxin.
Symptoms including rashes and irritation to the throat and lungs could appear between 10 minutes and three hours post-ingestion.
Mcilroy said in previous years, similar blooms were reported at Musick Point at Bucklands Beach, and nearby at Eastern Beach and Howick.
Some of the earliest records went back to 1950s-era surveys, Mcilroy said.
In the 1970s, Okeania spp was described as a seasonally dominant species on rock platforms around Motukaraka Island, a 14-acre island off the coast of Beachlands.
Earlier this century, the blooms frequently appeared around Beachlands and nearby Ōmana.
