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Scientific research and technical advice
Find scientific research and technical reports on exotic caulerpa in New Zealand - its biology, impacts, surveillance results and management measures, plus minutes of meetings of the former Exotic Caulerpa National Advisory Group.
Find scientific research and technical reports
A strategic surveillance system for exotic caulerpa spp. in New Zealand (July 2026)
In this report, Earth Sciences New Zealand (ESNZ) outlines a surveillance strategy with a risk-based framework combining habitat suitability, spread pathways (ocean currents and vessel movements), site value, and surveillance history to prioritise where surveillance should occur.
A strategic surveillance system for exotic caulerpa spp. marine algae in New Zealand [PDF, 9.6 MB]
Vertigo3 as a surveillance tool for exotic caulerpa (June 2026)
Flying Fish Technologies examine the use of underwater piloted gliders and report that they can rapidly cover large areas, far exceeding what is done by divers working with remote operated vehicles. A machine learning based detection model achieved approximately 92% accuracy in simple habitats with high exotic caulerpa density or abundance, but weaker accuracy in coastal, turbid (stirred-up) or visually complex habitats.
Rapid targeted exotic caulerpa surveillance – Hauraki Gulf and Coromandel (January 2026)
This research report by Earth Sciences New Zealand presents the findings of a rapid, targeted surveillance survey for exotic caulerpa during November 2025 to improve understanding of the current distribution and extent, confirm presence or absence at prioritised locations, and identify any large or previously undiscovered infestations.
Rapid targeted exotic caulerpa surveillance [PDF, 8 MB]
Advanced surveillance of exotic caulerpa – Using computer vision for automated detection (April 2025)
A research report by NIWA (now Earth Sciences New Zealand) documents the development and application of remote operated camera systems and associated computer vision (i.e. Artificial Intelligence [AI]) algorithms for the detection of exotic caulerpa.
Advanced surveillance of exotic caulerpa [PDF, 5 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.
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]
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]
Understanding the impact of exotic caulerpa on commercial and recreational fisheries species (August 2026)
This report by Earth Sciences New Zealand (ESNZ) finds that there are no direct major impacts on scallops at current low caulerpa cover, but juvenile snapper nursery habitat could be at risk if caulerpa invades seagrass. Further research is recommended.
Progression, ecological context, and emerging impacts of exotic caulerpa on reefs of the outer Hauraki Gulf, Aotearoa New Zealand (June 2026)
This University of Auckland research finds active spread of exotic caulerpa on offshore reefs, but low density on hard substrates. Impacts are currently low but could increase if dense meadows form.
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, 2.8 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]
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 – 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]
Sexual reproduction of caulerpa parvifolia (August 2026)
This Cawthron Institute research finds that high light levels trigger sexual reproduction and die-offs in caulerpa parvifolia and that gametes develop into young algae within approximately 35 days.
Sexual reproduction of caulerpa parvifolia (Chlorophyta; Caulerpaceae) [PDF, 1.8 MB]
Understanding exotic caulerpa growth, biomass and population dynamics in Aotearoa New Zealand (September 2026)
Cawthron Institute finds that exotic caulerpa die-offs are temporary, populations are rebounding and this is generally occurring on stable substrates such as rock and reef. They also found that in areas of dense kelp exotic caulerpa growth is supressed. Fragments on anchors remain the key means of spread, and of the 2 exotic caulerpa species in New Zealand, C. parvifolia is more widespread than C. brachypus.
Genetic sequencing of exotic caulerpa in New Zealand (May 2026)
This Earth Sciences New Zealand (ESNZ) report documents the history and genetic sequencing of caulerpa brachypus and caulerpa parvifolia in New Zealand. They also provide a key to the features people can use to identify visually between the 2 species.
Caulerpa brachypus and Caulerpa parvifolia (Caulerpaceae, Ulvophyceae) in New Zealand [PDF, 5.9 MB]
Fragmentation in exotic caulerpa (June 2026)
Laboratory-based experiments on caulerpa parvifolia by University of Auckland find fragments are highly resilient to cold and darkness and regenerate quickly in warmer temperatures and light. In a simulation of boat anchor locker conditions, with no sediment, fragments remained viable for 12 to 24 hours.
Exotic caulerpa biomass reduction and large-scale removal scenarios – Post workshop report (April 2026)
To support the development of a strategy for local population control, and, where feasible, small-scale elimination, Biosecurity New Zealand convened a panel of national and international experts for a local elimination case-study workshop. This report summarises the outcomes of the workshop which included presentations and a case studies session where participants worked through a range of location-based scenarios.
Exotic caulerpa biomass reduction and large-scale removal scenarios [PDF, 876 KB]
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.
Effect of UV-C on native and invasive flora and development of a Marine Macroalgae Health Index (MMHI) (May 2026)
This Earth Sciences New Zealand (ESNZ) research reports that successive treatments with UV-C strongly stresses exotic caulerpa and causes biomass loss. However, it also affects red algae and native caulerpa.
Development and application of contained chlorination treatments for removal of exotic caulerpa (September 2026)
Research by Cawthron Institute finds chlorine treatment chambers reliably achieve and maintain target concentrations. Bleaching is observed in both Undaria pinnatifida (invasive kelp) and exotic caulerpa but complete death is uncertain and more time is needed to assess if there is any recovery after bleaching.
Applying emerging UV-C technology for the sustainable long-term, non-chemical control of invasive caulerpa (August 2025)
Advanced Aquarium Technologies developed and tested a small mobile rock and reef unit alongside their larger ROV driven V-C tool. They report that UV-C is a useful suppression tool for exotic caulerpa but resilience means multiple exposures are needed. Further work is needed to confirm minimise the impacts on non-target species and test the scalability of the technology.
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]
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.
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.
Find out more about the development of removal/management tools
Technical advice on caulerpa brachypus and C. parvifolia (exotic caulerpa) (April 2025)
This document was prepared by MPI’s Biosecurity Risk Advice team to present the known information about exotic caulerpa, drawing from available scientific research.
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.
- Prevent establishment outside the current infested region.
- Slow the spread within the existing infested areas.
- Protect and restore the mauri of high-value affected sites where it can’t be eliminated.
- Minimise impacts on the environment, communities, and customary practices.
- Increase understanding of the behaviour and impacts of exotic caulerpa.
- 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]
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]