Millions Being Thrown At Bay Of Islands' Caulerpa Control As Pest Seaweed Spreads

Sunday, 2 March 2025, 9:01 pm
Article: Susan Botting - Local Democracy Reporter

The government is throwing more than $6 million at developing world-first industrial-scale technology to fight caulerpa as the invasive seaweed is confirmed at major tourist hot spot Bay of Islands motu for the first time.

Biosecurity Minister Andrew Hoggard said big strides were being taken with the $6.2 million development of the new technology at Omākiwi Cove and $3.8 million for other technology at two other New Zealand locations to control the invasive exotic seaweed.

Hoggard said funding was based on earlier project success.

Northland Regional Council (NRC) confirmed this week that caulerpa had been found at six new locations in the eastern Bay of Islands Ipipiri island group, about six kilometres from Paihia.

It has been found at Urupukapuka Island's major boating anchorages Paradise Bay and Otiao Bay (Entico Bay) and Moturua Island's Army Bay as well at two locations around adjacent Motukiekie Island.

NRC chairperson Geoff Crawford said the new finds were disappointing, but there had always been the potential for them to happen.

Caulerpa eradication was still possible - with the help of technology being developed in the Bay of Islands' Omākiwi Cove.

Five of the new sites are outside the Bay of Islands 1000ha caulerpa anchoring ban area in June 2021.

They are the first confirmed caulerpa spread since New Zealand's only mainland caulerpa infestation was confirmed at Omākiwi Cove, Te Rāwhiti in May 2023 about three kilometres away.

A new infestation has also been identified on the northern edge of the anchoring ban area, close to the islands.

Omākiwi Cove has been the site of groundbreaking eradication trials since May 2023.

Crawford said the new government funding was essential in the race to develop robust tools to fight caulerpa, even as the invasive pest seaweed had spread to the Ipipiri Islands.

He said it was important to stay focused in the face of this spread.

"It's disheartening to hear. But unfortunately, until we develop these tools, eradication isn't likely.

"Without technology like the underwater tractor unit we wouldn't have anything to fight invasive caulerpa," Crawford said.

He said there had always been the chance that caulerpa would spread outside the anchoring ban area.

The government money will go towards upscaling successful Omākiwi Cove caulerpa removal trials to an industrial scale.

"At present we're capable of harvesting 30 tonnes of caulerpa a day," he said.

"We're hoping to be able to expand that to 600 tonnes a day. That quantity's about the same in volume as a typical three-bedroom house."

One of the biggest challenges would be working through how to deal with the increased quantity of caulerpa brought up onto the vessel in the new regime, Crawford said.

NRC would continue linking with Ōpua-based marine contractor Johnson Bros, which had been working with the council and local mana whenua partners Ngāti Kuta and Patukeha hapū to remove exotic caulerpa in Omākiwi Cove.

The new tool called a 'submersible dredge planer' would operate remotely on the seafloor and aimed to remove exotic caulerpa in a single pass.

It would be part of a new larger system including the remotely operated planer, upsized dredge head, pumping arrangements, GPS position system, dredge spoil processing plant and disposal system.

Crawford said the new technology was for getting rid of caulerpa on soft sandy seafloor.

Other work to control it on surrounding rocky areas along shorelines also needed developing.

NRC will also be supporting two other $3.2 million government-funded projects - developing ultra-violet light irradiation tool to kill the pest seaweed and a chlorine treatment chamber that will hover over the seabed.

Exotic caulerpa has been found in nine different locations in the upper North Island since first being discovered on Aotea Great Barrier Island in July 2021.

LDR is local body journalism co-funded by RNZ and NZ On Air.

© Scoop Media

Local Democracy Reporting

Content from the Local Democracy Reporting (LDR) service is published by Scoop as a registered New Zealand Media Outlet LDR Partner.