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Exotic Caulerpa: Threat to our coastal ecosystems

Exotic Caulerpa has made its way to our shores and the Ngāti Manuhiri Settlement Trust are putting the wero out to our whānau, communities, and partners to take action so we can eradicate this invasive species from our beautiful coastline.

Experience overseas with Caulerpa (Caulerpa taxifolia) in the Mediterranean (Thibaut and Meinesz), USA (Williams and Grosholz), and Australia (Creese et al.) is that Caulerpa can rapidly spread, dominating broad areas of the intertidal and subtidal marine coastal ecosystem down to depths of 50m, displacing indigenous biodiversity as it spreads. Caulerpa spreads fast over vast areas and colonises a range of environments from soft sediment to rocky reef. It spreads both from dislodged fragments and sexual reproduction.

Exotic Caulerpa (Caulerpa brachypus and Caulerpa parvifolia ) was discovered at Aotea / Great Barrier Island and Ahuahu / Great Mercury Island. The estimated footprint of the outbreak in Okupu / Blind Bay (Aotea) from the first survey performed in August 2021 was 88 ha. It has since spread to other western harbours on the island. The outbreak at Ahuahu was estimated to extend to 3.2 ha at that point in time.

Webinar Next Week : California Invasive Species Action Week Lunchtime Talks

Our Californian friends have managed to eradicate caulerpa and are sharing their lessons learned in an online webinar from 7:00 am - 8:00 am on Tuesday, June 6, 2023, for us in Aotearoa.

This presentation will provide an overview of infestations of marine algae in the genus Caulerpa, with a focus on introductions discovered in California. The highly invasive strain of Caulerpa taxifolia was discovered in two lagoons in Southern California in 2000. Based on its aggressive nature and the displacement of native marine resources observed upon its discovery, it was recognized that the infestations potentially posed a major threat to coastal ecosystems, and recreational and commercial uses dependent upon coastal resources. A rapid response plan was quickly developed, funding promptly secured, and C. taxifolia was successfully eradicated at a cost of over $7 million and 7 years. In 2021, Caulerpa prolifera was confirmed growing near the mouth of Newport Bay. Attempts to mount a similarly prompt and comprehensive response have been hampered by limited funding, as well as less government and public engagement. The presentation will discuss lessons learned and the importance of an immediate and sustained response when invasive species are detected early on.

Presented by Rachel Woodfield.


Exotic Caulerpa at Aotea. Photo: Dr. Irene Middleton, NIWA

To date Biosecurity NZ have established Controlled Area Notices (CANs); assembled an independent expert Technical Advisory Group (TAG); commissioned NIWA to do survey work; conducted trials on eradication methods; and engaged with iwi (Ngāti Rehua and Ngāti Hei) on establishing rāhui and a Caulerpa Ambassador programme, monitoring for beach cast and driving local awareness.

The TAG determined that the Okupu / Blind Bay infestation was well established and at a scale where it was already beyond eradication. Eradication was deemed impossible with the size of the populations and the tools available (Biosecurity New Zealand).

From Biosecurity NZ / Tiakitanga Pūtaiao Aotearoa, Exotic Caulerpa seaweed at Aotea Great Barrier Island and Ahuahu Great Mercury Island - Presentation, May 2022

More information about exotic caulerpa:

WMP Caulerpa Presentation April 23 (1)
Download PDF • 6.01MB

Letters to the Minister
Letter to Ministers O'Connor and Prime - Exotic Caulerpa Ramifications for marine active h
Download • 614KB
2023 0518 Letter to Minister O'Connor re Caulerpa elimination
Download PDF • 1.58MB

Contact us

Ngāti Manuhiri Settlement Trust

Attention to: Te Wero



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