The government has announced three new projects to refine control methods for the invasive caulerpa seaweed in the upper North Island, including Great Barrier Island. Biosecurity Minister Andrew Hoggard says the initiatives build on previous efforts.
“These new projects focus on methods that showed progress in an earlier phase of work,” said Minister Hoggard.
Previous attempts to control caulerpa have had mixed success. Dredging has worked in sandy areas but struggled in rocky reef environments like Great Barrier. Ultraviolet (UV) light treatments have only been effective against a species in the inner Hauraki Gulf, while chlorine-based treatments have shown the most success overseas.
The largest contract, worth $6.2 million, has been awarded to the Northland Regional Council to develop an advanced mechanical suction dredging system.
“We know from the first phase of the accelerated programme that this method can remove exotic caulerpa from sandy areas of the seafloor, and now we’re looking to increase its effectiveness.
“The project team is developing a new tool called a ‘submersible dredge planer’ which will operate remotely on the seafloor, rather than from a barge, and will remove caulerpa in a single pass.
“The new system will include a dredge head, pumping arrangement, GPS positioning system, dredge spoil processing plant, and disposal system,” Hoggard said.
A second project, receiving $2 million in funding, focuses on the development of an ultra-violet light (UV-C) irradiation tool to kill caulerpa.
“This contract has been awarded to Advanced Aquarium Tech who aim to create a cost-effective option to treat exotic invasive caulerpa without needing to deploy SCUBA divers.
“It will require minimal labour, operate off a small vessel, and be able to be used at any depth of water from intertidal zones to 40m depth,” Hoggard explained.
The third project, receiving $1.9 million, involves the creation of an underwater treatment chamber that utilizes chlorine.
“This chlorine treatment chamber, being developed by Commercial Dive Specialists, will be able to hover over the seabed and pass over rocks and other obstacles without getting stuck,” Hoggard stated.
Exotic caulerpa has been detected in nine different locations across the upper North Island over the past three years. Since its initial discovery at Aotea/Great Barrier Island, authorities have been working to understand and contain its spread while developing long-term management solutions.
“No other country has come up with a feasible solution to this pest, but we’re determined to explore every option for future control,” said Hoggard.
