NZ Geographic spotlights Caulerpa — and Rehabitat

New Zealand Geographic has published a major feature on exotic Caulerpa, and Rehabitat — our contained chlorination system — is part of the story.

Grappling with the shapeshifter, written by Bill Morris with photography by Richard Robinson, follows the people working on the problem: divers, scientists, iwi and community groups, and the teams developing new tools. We're proud to sit alongside them.

A hard opponent

Two exotic species, Caulerpa brachypus and Caulerpa parvifolia, were first found at Aotea/Great Barrier Island in 2021. They have since spread through the Hauraki Gulf and into the Bay of Islands, where one infestation at Omakiwi Cove covered 16 hectares.

The article makes clear why Caulerpa is so difficult to deal with. It can regrow from fragments too small to see, survive weeks without light, and live for hours out of water in a damp anchor locker. Biosecurity New Zealand's focus has been on clearing heavily infested areas and stopping further spread. MPI has invested $34 million so far in surveillance and control tools to support that work.

Where Rehabitat fits

Rehabitat began when Kaeden Leonard and Derek Richards at Northland Regional Council asked CDS director Brook McRae for innovative solutions to the Caulerpa crisis.

| As Brook told NZ Geographic: “Systems are my passion.”

The result is an inflatable mat that covers a rectangle of seafloor and draws down to create a sealed, negative-pressure chamber. The space underneath is then flooded with a chlorine solution, treating the Caulerpa inside while keeping the treatment contained. The system is built to scale up to larger areas.

The article covers the investment behind it. Brook and Sarah McRae put $200,000 of their own money into developing the system, and MPI granted around $1.9 million to refine it. Rehabitat is one of three tools in MPI's latest funding round, alongside UV light and suction dredging.

The feature also reports an independent Cawthron Institute finding: within two to four months of treatment, life on the seabed returns to normal. As Brook puts it, chlorine is used for marine biosecurity around the world, and “the sea is very used to handling chlorides.”

Building the toolbox

Our position is simple, and Brook summed it up in the article: “We want to build the tools for eradication, and then let people decide if they want to use them.” Whether the goal is protecting a marine reserve, clearing a marina, or catching a new incursion early, decision-makers need proven options ready to go. As University of Auckland marine scientist Andrew Jeffs notes in the piece, very few countries have this kind of technology available.

Rehabitat was also recognised this year with the NZ Marina Operators Association Outstanding Initiative Award (Associate Member).

Thank you very much to Bill Morris and Richard Robinson for including us. We recommend reading the full story at New Zealand Geographic.

Want to know more about Rehabitat or talk to us about a biosecurity project? Get in touch with the CDS team.