Exotic Caulerpa - FAQ

Where is it at Waiheke?

Kei hea ētahi wāhi ki Waiheke?

Exotic Caulerpa is known to be at three main zones on Waiheke’s Northern coast. These areas are both sides of Thompson’s Point and in Woodlands Bay, Onetangi. There have been smaller examples detected across Onetangi bay and recently a small discovery was made near Nani Island, Mawhitipana Bay. In total, the incursion area measures about 400 hectares of varying density and spacing. We have mapped all known surveys on our website here.

What is it & what does it look like?

He aha tēnā mea? He aha te āhua nei?

EC is a non-native invasive green seaweed from the caulerpa family which has stolons (running roots) spread under the loose sea floor then paddle-shaped vertical blades which pierce the substrate or attach to rock as it forms dense smothering mats.

What is it & what does it look like?

He aha tēnā mea? He aha te āhua nei?

EC is a non-native invasive green seaweed from the caulerpa family which has stolons (running roots) spread under the loose sea floor then paddle-shaped vertical blades which pierce the substrate or attach to rock as it forms dense smothering mats.

Where does it come from and which one do we have?

Nō hea ēnā mea? Nō tēhea i roto i te moana?

It is native to the Indo-Pacific region, and can be found from Africa to Australia, the Pacific Islands and southern Japan. A sample tested from Waiheke was found to be Caulerpa Parvifolia.

When was it first found on Waiheke?

Nōnāhea te wāhi tuatahi o Waiheke?

On 29th July 2023, a WMP project crew including Ngāti Paoa ki Waiheke first detected EC with a Remote Operated Underwater camera (ROV) contractor. This was during the third of six initially planned days of checks and was the result of considering the more likely depths and substrates based on knowledge of Waiheke’s coast and learning from detections in other areas such as at Kawau Island.

Have we looked at other locations?

E hia ētahi wahi ke ō Waiheke?

Yes, we have checked other locations such as Owhanake Bay, Oneroa Bay, Palm Beach, Owhiti, and further East including Te Matuku Bay on the Southern coast.

Are you still looking?

Ka titiro tonu koe?

In May 2024 the current funding commitment for 5 additional series of ROV underwater surveys to continue surveillance on the edges of the known incursion sites was exhausted. We are seeking assistance to expand this programme. MPI has contracted NIWA to test surveillance techniques and new technology at Waiheke as part of the Governments Accelerated programme which runs until June 2024.

Who else has looked?

Ma wai e rapu ana?

Ngāti Paoa divers were active during August 2023 viewing and conducting treatment experiments on the incursion zone of West-Thompsons point. NIWA divers verified the WMP discovery and returned later in 2023 to work towards understanding the limit of the functional edges of the sites during additional surveys. NIWA has since checked some locations on the Eastern & Southern coasts as part of their mahi.

How did it get here?

Me pehea i tae ai ki reira?

It is considered likely that it was carried to New Zealand after contact with the seafloor in another incursion area. Theories including attachment to fishing gear, ropes, anchors, chains, aquarium, fishing or diving equipment have been considered as well as being carried on waves or ocean currents. There hasn’t been a conclusive explanation whether it arrived in Aotearoa via human or other environmental pathways.

Is it just Waiheke Island?

Ko Waiheke noa iho?

No, Aotea Great Barrier (2021), Ahuahu Great Mercury (2022), Bay of Islands (2023) and Kawau Island (2023), Rakino (2024), Coromandel (2024) and the Mokohīnau Islands (2024) are dealing with this as well. In June this year, a patch of less than sqsquare metre was found and removed in Leigh harbour.

Why is it bad?

He kino? He aha ai?

EC takes over wherever it appears. Stimulated by light and warm seas outside of its natural home it smothers other life forms as grows a dense carpet across the seafloor. Creatures that were trying to regenerate or thrive are displaced leading to a monoculture of unwanted weed. In New Zealand waters it is known to grow rapidly as much as 30mm per day and only a 10mm tiny fragment broken away can survive to live and expand at a new location. Without intervention this introduced species will change the enjoyment and resource of the moana as we know it. The bays of Waiheke are taonga and important for the recreational and economic well-being of the community. This incursion is a major threat to all the creatures for whom Waiheke is home.

Can we get rid of it?

Ka taea e tātou te whakakore atu?

There is an example of a successful removal programme in California. Despite theirs being in a smaller and more contained area, the Waiheke Marine Project is working on the basis that it is possible here too. The Northern Regional Council is also taking this removal approach. Removal so far has used a combination of suction equipment and diver hand removal. Treating the seaweed in place is also being trialed. Ngāti Paoa Iwi Trust are developing and testing woollen benthic mats and other forms of tarpulins with salt and chlorine granules have been used. Another treatment method being researched and showing promise is exposure to Ultraviolet (UV-C) light. It is likely to take several years and require well-resourced coordinated systematic and determined action.

Does anything eat it?

Ma wai e kai ai?

In our region, nothing eats Exotic Caulerpa in any known significant way – trials are underway with kina (sea urchins), however early results are not encouraging.

Are there other uses?

Ētahi atu whakamahinga?

Consideration of this is ongoing including the potential for turning the weed into liquid fertilizer or in the production of biofuel. Some preliminary trials have been conducted on Aotea Great Barrier to compost it once it has been removed from the ocean. However, because it is classified by agencies as noxious and as an ‘unwanted species’, there are restrictions on moving & using it.

What if we find some on our coastal walks?

Mehemea i kitea, he aha te mahi?

Take a photo, then place it in a secure bag and bin it. Then, remember where you saw it, and report it here.

Where on Waiheke can I take it?

Heoi anō, mēnā kei a koe, whiua kī hea?

Please place it in a secure bag in any secure residential bin, commercial bin at wharves, or take it to the Waiheke Community Resource Recovery Park on Ostend Rd.

Can it be composted?

Onepōpopo pea?

Yes, trials at Aotea Great Barrier are showing encouraging results. Please ask us if you would like additional information.

What lab testing is underway?

He aha ētahi mahi pai?

A UV-C light test on samples from Waiheke & Aotea is one of the ideas being explored to see if it stunts growth or kills it completely. MPI are understood to have been conducting tests since 2021 as well however the scope and outcomes of these are unknown.

Who is the responsible Government agency overall?

Tēhea te roopu kawanatanga i mahi pai?

The Ministry of Primary Industries (Biosecurity NZ) and Auckland Council. Who is actively working on this at Waiheke? Mā wai e mahi ana ki tēnei kaupapa? Ngāti Paoa have placed a rāhui around the outbreak areas. This restricts anchoring and other activities that may disturb the seabed within the rāhui zone. Waiheke Marine Project volunteers are supporting Ngāti Paoa in their efforts in combating Exotic Caulerpa and have formed a Marine Monitoring panel which includes Ngāti Paoa Ki Waiheke, Waiheke Local Board and members of the community. The panel meets every three weeks and actively participates in ongoing discussions on Hauraki Gulf-wide treatment and eradication programmes.

What does it dislike?

Kāore e rite?

Exotic Caulerpa dislikes the cold. Being deprived of salt water, and darkness are its enemies & of course being removed from the sea, bagged & binned or composted.

What’s the future plan?

He aha te māhere ki mua?

Ngāti Paoa Iwi Trust received support and permissions from agencies for a limited removal and treatment programme in February 2024. This was a trial combination of diver directed suction dredge removal, covering with natural fibre sheets and diver hand removal. The removed biomass was treated at the Old Blackpool School site before being disposed of on land. The Waiheke Marine Project has a Waiheke focused communications initiative and is continuing to collaborate with agencies such as MPI and Auckland Council plus groups across the regions such as Revive Our Gulf and the Aotea Great Barrier Environmental Trust and the Hauraki Gulf Forum. The outcomes of the Government’s Accelerated Programme tests will be key to understanding the support available to communities beyond June 2024.

How can we help?

Me pēhea i awhina ai tātou?

As individuals we can report any sightings from land or sea and follow MPI’s guidance. Waiheke Marine Project are currently seeking funding support to increase surveillance, the frequency of treatment and to explore engaging commercial and volunteer diving squads.

Please contact us if you can contribute

Updated August 2024