Auckland Council warns public to avoid black algae on two Waiheke Island beaches and Kawakawa Bay

Last Updated : 20 Feb 2024
Algae Blackpool Waiheke
The cyanobacteria Okeania spp on Blackpool Beach, Waiheke Island.

Auckland Council is warning people to avoid black algae present on two Waiheke Island beaches as well Kawakawa Bay on Auckland’s mainland.

The cyanobacteria Okeania spp (previously classified as Lyngbya majuscule) has been detected on beaches at Surfdale and Blackpool on the southern coast of the island. This is the same algae that was present on the island’s coast last summer. 

In December 2023, laboratory testing of samples of the algae confirmed the presence of Okeania spp and the toxin Lyngbyatoxin-A in the algae on the two Waiheke Island beaches. Auckland Council erected warning signs on these beaches and began a clean-up operation in late January, expected to last six weeks.

In February 2024, the same black algae (Okeania) has washed up at Kawakawa Bay in Auckland's east. Auckland Council have erected warning signs and is monitoring the situation.

The Auckland Regional Public Health Service advises that the algal bloom could lead to skin, eye and respiratory irritations. 

The public are advised not wade in the water or touch the algal material at the affected beaches.  

Barry Potter, Auckland Council’s Director of Infrastructure and Environmental Services said the council is monitoring the situation. 

“We will continue to monitor the scale and impacts of this naturally occurring phenomena in case any further advice or intervention is required. 
“We understand the public may have concerns around this news and we thank them for their patience and cooperation.” 

Deputy director-general of New Zealand Food Safety (NZFS), Vincent Arbuckle, says NZFS is advising the public not to consume shellfish from Surfdale and Blackpool beaches.  

“Affected shellfish include bivalve shellfish such as mussels, oysters, tuatua, pipi, toheroa, cockles and scallops, as well as pūpū (cat’s eyes), Cook’s turban and kina (sea urchin). It is important to remember that cooking does not make the shellfish safe to eat. Finfish are not affected by this public health warning, but people should gut the fish and discard the liver before cooking.” 

Auckland Council contractors will start removing the algae from Surfdale and Blackpool beaches in the new year. The clean-up operation is expected to take approximately six weeks.

Staying safe at affected beaches 

The beaches where the algae is present remain open to the public but Auckland Council advises the following: 

  • Avoid contact with the algae, including wading in affected areas, as it could lead to skin, eye and respiratory irritation 

  • If you feel unwell as a result of contact with the bloom, you should contact your doctor, or call Healthline on 0800 611 116 

  • Do not gather or take algae from the beach for things like using on your garden  

  • Keep dogs away from the algae and any decomposing material which could cause a reaction 

  • Do not gather or consume shellfish from the affected beaches. 

Frequently asked questions about Cyanobacteria 

What are Cyanobacteria? 

  • Cyanobacteria (or blue-green algae) are naturally occurring microscopic organisms that live in a range of aquatic environments, from near-pristine to those more impacted by land use. 

Are Cyanobacteria harmful to humans? 

  • Lyngbya species of Cyanobacteria (including Okeania spp. and Moorea spp) are known to produce toxins – collectively referred to as lyngbyatoxins – which could lead to skin, eye and respiratory irritations. 

Do Cyanobacteria originate from outside New Zealand? 

  • No. Cyanobacteria are naturally occurring in New Zealand waters. 

Are Cyanobacteria common in New Zealand waters? 

  • The cyanobacteria Okenia spp occurs naturally throughout the Hauraki Gulf. Blooms of the filamentous cyanobacterium identified at the time as L. majuscula have been reported in various parts of the Hauraki Gulf particularly in the Omana Beach area. There have also been reports of previous summer blooms at sites in eastern Auckland in the Hauraki Gulf (Musick Point, Eastern Beach and Howick) as well as sites in the Manukau Harbour (Kaitarakihi Bay) and at North Head in the Waitematā Harbour. Some of the earliest records of Lyngbya spp. go back to surveys in the 1950s and in the 1970’s it was described as a seasonally dominant species on rock platforms around Motukaraka Island. Through the 2000s there were regular occurrences of blooms around the Beachlands and Ōmana areas. 

Why is the Cyanobacteria occurring now?

  • The drivers of Cyanobacterial blooms are complex and it is very difficult to predict or explain where they may occur, as well as their size and duration. 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), followed by the right conditions to dislodge blooms (ie stormy weather). Once dislodged, factors such as the tidal conditions and wind direction need to be understood to predict where blooms may eventually be deposited. These requirements mean blooms most commonly occur during spring and summer, and are a natural phenomenon in shallow, productive coasts. It is likely that a perfect combination of conditions in recent months has resulted in the current washed up bloom on Waiheke Island.

What impact does Cyanobacteria have on the environment? 

  • Some cyanobacteria blooms can have serious impacts on aquatic ecosystems in general including potential toxic effects due to smothering and shading. However, there is a lack of research when it comes to the environmental impacts of Lyngbya spp. 

What research is being carried out into the cyanobacteria?

  • Working closely with Auckland Council, the Cawthron Institute has identified the dominant component of the cyanobacterial mats as Okeania. Dr Laura Biessy at the Cawthron Institute is carrying out analyses to characterise the species responsible for these blooms on Waiheke Island. There is a lack of research surrounding the ecology, toxicity and impact on the environment of benthic cyanobacterial species such as Okeania. Dr Biessy is currently trying to isolate and culture this species to enable future research, in particular the ecology of the species, its preferred growing conditions (temperature, salinity, nutrients, etc.) and habitat. These answers would allow us to predict when future blooms might occur and what could be done to mitigate these blooms. The Cawthron Institute is also currently testing shellfish collected from the affected beaches on Waiheke Island for lyngbyatoxin-A accumulation, as this could impact human and ecosystem health.
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