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Impacts of exotic caulerpa on biodiversity and community structure (July 2025)

This study by NIWA (now Earth Sciences New Zealand) found that exotic caulerpa growing in soft sediment areas is supporting a higher diversity and number of species than were found in native seagrass or bare sediment.

Impacts of exotic Caulerpa on biodiversity and community structure [PDF, 1.7 MB]

Impacts of exotic caulerpa on Aotearoa’s reefs (June 2025)

This University of Auckland study found that in native reef ecosystems, exotic caulerpa, which is an algae, was playing a role similar to native algal turf species. The researchers say exotic caulerpa appears to cause little ecological disruption, acting as a secondary habitat (a habitat that has been affected by humans but supports a lot of species and functions).

Understanding the ecology and impacts of exotic Caulerpa on Aotearoa’s reefs [PDF, 4.4 MB]

Evaluation of exotic caulerpa biomass reduction at Omakiwi Cove (June 2025)

At the time of the above research, no significant reduction was found at Tryphena Harbour, Aotea or in Omakiwi Cove in the Bay of Islands. After further community reports, supplementary dive investigations revealed reductions at these 2 locations. This report looks at the 2 additional locations.

Omakiwi Biomass Reduction Report [PDF, 1.2 MB]

Evaluation of exotic caulerpa biomass reduction (June 2025)

This report from NIWA investigates public reports of caulerpa reduction at 2 Aotea locations and at Waiheke Island and confirms a significant loss of coverage in previously heavily infested areas. The declines were most notable on soft, sandy seabed.

Evaluation of exotic Caulerpa biomass reduction [PDF, 9 MB]

Summaries of known exotic caulerpa locations and Biosecurity New Zealand-funded removal trials or missions (October 2024)

These 2 reports were compiled by Biosecurity New Zealand as advice to the National Exotic Caulerpa Advisory Group.

Summaries of known exotic caulerpa locations and Biosecurity New Zealand-funded removal trials or missions (October 2024) [PDF, 352 KB]

Delimiting surveillance at Ahuahu Great Mercury Island (May 2024)

A report from the Bay of Plenty Regional Council on surveillance to understand the extent of the exotic caulerpa population at Ahuahu Great Mercury Island.

Delimiting surveillance at Ahuahu Great Mercury Island (May 2024) [PDF, 783 KB]

Perimeter management of exotic caulerpa in Port Fitzroy, Aotea (May 2024)

Contracted by Auckland Council, Bay Underwater Services NZ Ltd carried out an operation to manage exotic caulerpa in the Port Fitzroy area of Aotea Great Barrier Island. This report details the work and findings.

Perimeter management of exotic caulerpa in Port Fitzroy, Aotea (May 2024) [PDF, 899 KB]

Northland Regional Council wider surveillance for exotic caulerpa (April - May 2024)

A report that details surveillance for exotic caulerpa in the Northland region at known anchorages. This surveillance recognises that exotic caulerpa is most likely spread entangled in or attached to anchors and equipment.

Northland Regional Council wider surveillance for exotic caulerpa (April - May 2024) [PDF, 1.6 MB]

Perimeter management of caulerpa infestation in Te Rāwhiti, Northland (May 2023 – April 2024)

This Northland Regional Council report documents work to understand the spatial extent of exotic caulerpa in Te Rāwhiti and efforts to reduce that extent by removing infestations found at the outer edges of the Controlled Area zone there.

Perimeter management of caulerpa infestation in Te Rāwhiti, Northland (May 2023 – April 2024) [PDF, 2.4 MB]

Technical advice on a long-term management strategy for exotic caulerpa (February 2024)

A further group of technical advisors met in July 2023 to advise on a long-term strategy for exotic caulerpa management. While recognising strong community desires to eradicate exotic caulerpa, the group reports that this is not currently a realistic objective. It set 6 objectives for future management.

  1. Prevent establishment outside the current infested region.
  2. Slow the spread within the existing infested areas.
  3. Protect and restore the mauri of high-value affected sites where it can’t be eliminated.
  4. Minimise impacts on the environment, communities, and customary practices.
  5. Increase understanding of the behaviour and impacts of exotic caulerpa.
  6. Ensure investment in exotic caulerpa management and marine biosecurity enables the development of better tools and capability for more effective marine responses.

Exotic caulerpa strategic Technical Advisory Group report [PDF, 12 MB]

Impact of exotic caulerpa on native species – Phase 2 report (December 2023)

NIWA returned to the 18 permanent sites in June 2023 and found that exotic caulerpa cover had increased significantly at shallow sites in Okupe/Blind Bay but was variable at deeper sites. As in Phase 1, taonga species kina and tipa (scallops) appeared to have been negatively affected in areas with dense exotic caulerpa.

However, this research is part of an ongoing programme, and as such, this is an interim report. It finds that continued monitoring is required to allow robust conclusions on the role exotic caulerpa is having on the functioning and population dynamics of target species and habitats.

Impact of exotic caulerpa on native species at Aotea Great Barrier Island field report (trip 2) [PDF, 3.8 MB]

Impact of exotic caulerpa on native species – Phase 1 interim report (April 2023)

Biosecurity New Zealand commissioned NIWA to assess the impacts of exotic caulerpa on the ecosystem and taonga species at Aotea Great Barrier Island.

In a multi-year study, NIWA monitored 18 permanent sites in the 3 affected bays at the island – Blind Bay, Tryphena Harbour, and Whangaparapara Harbour.

They looked at any effects on native species, as well as how the caulerpa itself was affected by wave energy and light availability, including storms.

In the interim report, observations suggested that exotic caulerpa might be having a negative impact on the condition and population dynamics of taonga species. However, the report states that further sampling and analysis are required before the extent of any impacts on most of the habitats would be known.

Impact of exotic Caulerpa on native species at Aotea/Great Barrier Island – Phase 1 [PDF, 1.9 MB]

Technical advice on the response to the discovery of exotic caulerpa (February 2022)

Response actions and decisions are informed by scientific advice. Since the discovery of exotic caulerpa in New Zealand in 2021, groups of international technical and scientific advisors with expertise in marine algae, control methods, and Mātauranga Māori have convened to advise on the situation and recommended actions.

The first Technical Advisory Group (TAG) met in December 2021 to provide advice on the incursion in New Zealand and the most appropriate response to its discovery.

The group concluded that:

  • the scale of the New Zealand incursion is beyond that at which successful eradication has ever been achieved internationally
  • eradication within each infected area is not possible with the current set of tools available
  • the most appropriate course would be to aim for suppression and containment, with a long-term management plan required to limit further spread.

Technical advisory report: Caulerpa Great Barrier Island 2021 response [PDF, 951 KB]

Exotic Caulerpa National Advisory Group

This 13-member group was formed in June 2024 and included people from mana whenua, government agencies, fisheries, environmental organisations, and community backgrounds.

The group, which was disbanded in July 2025, was created to provide independent advice to guide the ongoing management of exotic caulerpa and oversee the development of a national strategy.

Minutes of meetings held by the advisory group

Find out about exotic caulerpa and what we're doing about it

Exotic caulerpa seaweeds in New Zealand

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