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Exotic Caulerpa

Caulerpa is a highly invasive seaweed that was discovered on the Great Barrier Island in 2021, and is now found in the western bays of the Mercury Islands and the Bay of Islands. It is potentially very damaging to the New Zealand North Island east coast marine ecosystems.

Caulerpa weed under water
Exotic Caulerpa. Photo: MPI

Biosecurity New Zealand likens Caulerpa to a marine version of foot and mouth; this is perhaps alarmist, however without a doubt it has proven to have had a devastating impact wherever it gets established. This potentially could affect everyone's way of life; cultural, social, environmental, and economic and should be a huge wake-up call for the government and all New Zealanders who live, work, or play in our coastal waters.

Caulerpa is native to the Indo-Pacific region, ranging from Africa to Australia, the Pacific Islands, and southern Japan. Caulerpa is also considered an invasive pest in Florida, California, and Martinique in the Caribbean - somehow it has hitched a ride into the New Zealand waters.

As confirmed by Scott Godwin, Senior Marine Biosecurity Advisor at Auckland Council, "Caulerpa has the potential to carpet the sea floor habitat where it is established, smothering anything in its path. In favourable conditions, it can spread rapidly, forming vast, dense beds or meadows. Caulerpa can grow from a small piece, to cover an area the size of a rugby field in a year’s time."

MPI is currently pursuing a management programme rather than trying to eradicate Caulerpa, however this is currently under review and an announcement is due in few months. For all you need to know, including the maps of controlled area notices (CANs), go to the Ministry for Primary Industries web page.

Caulerpa seaweed washed up on a beach at Great Barrier Island
Metres-long caterpillar-like swathes of bright green invasive Caulerpa seaweed washed ashore on the exquisite Okupu Beach in Blind Bay, Great Barrier Island. Photo: MPI

A diver inspecting some bunches of Caulerpa weed
It's crucial for boaties to identify Exotic Caulerpa and keep a watchful eye out, particularly when retrieving an anchor from the sea floor: "See weed, chuck it straight back." Photo: MPI

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