Invasive species of Caulerpa have now been found in three locations in Auckland. The Hauturu Supporters Trust is very concerned. Kate Waterhouse, Trustee and Chair of the Aotea Great Barrier Environmental Trust, writes. 

“What is so worrying is the way Caulerpa takes over any substrate – on Aotea it has been found on reefs and in sponge gardens, growing on scallops as well as on sandy and muddy bottoms. It has grown as deep as 40m and we still don’t understand how it’s going to behave in our waters as summer warms them up. It can grow 3cm a day in the right conditions – it really is terrifying to think of whole coastal ecosystems disappearing under Caulerpa meadows as has already happened on the west coast of Aotea Great Barrier. 

Spread of Caulerpa can happen when a fragment is moved to a new location on an anchor or fishing gear, or freely on currents. Overseas it has been spread when aquariums with Caulerpa are emptied into the sea. The real worry for Hauturu is that spread will occur from the Aotea infestations, either on boats or fishing gear, but possibly on currents. 

Ngāti Manuhiri have taken a strong lead and have been instrumental in bringing iwi and community groups together to understand how to combat Cauleurpa. Key is early detection through regular underwater surveillance.  The Caulerpa infestation at Kawau is not as established as others and surveillance of Hauturu’s waters will be very important to stop it establishing around the island. 

We are all hopeful that the incoming government will take the necessary steps to stop Caulerpa’s potentially devastating impact on our coastal ecology cultural and community values, and fishing. Scallops have been badly affected on Aotea and this is just one example of the ecological effects. NIWA research on changes at Aotea over the last two years is due soon, but it won’t be good news.”

How can you help? Help spread the word about exotic Caulerpa! 

Ngåti Manuhiri advises: 

The warmer weather is perfect for the invasive caulerpa seaweed to thrive so please keep spreading the word to everyone you know about this pest. 

Exotic caulerpa spreads across the seabed, suffocating our native seaweeds and upsetting the marine ecosystem our kaimoana need to thrive, threatening our ability to get our kai.

 It’s easily spread from small pieces caught up in boating or fishing gear and thrives in warmer water so it’s crucial everyone is watchful to prevent this plant spreading even further. 

If you see it:

  • Note the location and report it – freephone 0800 80 99 66 or use the online form at 
  • If it’s caught up in your equipment, take it home and bin it
  • Do not attempt to remove it if you see it underwater, note the location and report it. 
  • Tell other people in the area if possible, awareness is one of our best tools to stop its spread

Read past issues of Ngåti Manuhiri’s newsletter and subscribe here

Info from Auckland Council is here 

Biosecurity NZ’s Caulerpa information 

Information about marine biosecurity for boat operators


Photo / Irene Middleton – NIWA principal technician Crispin Middleton monitoring the exotic caulerpa infestation in Blind Bay, Aotea



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