Caulerpa covers rocks in Okipu Bay, Greater Barrier Island.
Photo: Luka Forman
Scientists who monitor Caulerpa’s spread on the Greater Barrier Island say they are beginning to see the invasive herb depart from the bottom of the sandy sea.
It is the Caulerpa that grows in the rocky reefs that is now proving the biggest challenge on the island, but it is expected that new technologies will also help fight marijuana there.
The exotic seaweed was first discovered in New Zealand in 2021, leading to a concern for its rapid growth and potential to bring together native marine species.
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Glenn Edney is an oceanic ecologist who leads regular diving research in Great Barrier Island since 2022, monitoring the health of marine life, including the spread of exotic Caulerpa.
In their recent research, they noticed a reduction in the total amount of Caulerpa in some places and a change in which the exotic weed was growing mainly.
“Caulerpa has basically moved away from soft substrate sand areas, and this varies from one place to another. But in general, it has retreated from these areas and is more concentrated in the areas of Recife.”
There were also some signs of Caulerpa and the ecosystem adapting to each other.
Edney said that during recent research they observed a kind of fish, the two demonstration points, using weed as part of the mating process.
“So this is an adaptation of the demonstrations. Caulerpa may be covering the normal places of nests, such as coral territory … seems to be very well -sued … We were doing research and I was able to film a woman down and lying eggs, and the male fertilizing eggs.”
This made him cautiously optimistic, he said, but it was too early to draw conclusions about the long -term effects of Caulerpa in the ecosystem.
Meanwhile, in Northland, the exotic caulerpa was found at several new points in the islands bay outside the controlled area warning, where the anchor is not allowed.
Caulerpa growing in rocks in the islands bay.
Photo: Supplied / Rana Rewhha
Northland Regional Council President Geoff Crawford said it was disappointing that the herb spread to the controlled area, but not a big surprise.
“It’s not a large area. There are currents passing and tides.”
“It’s not uncontrollable, they are just in random areas, so we are quite confident that once we get our new technology we are currently creating, we will control it quickly.”
The fight was being supported by a US $ 10 million government concession to increase existing dredging and pumping methods, and developing ultra violet light treatments and a chlorine chamber to kill Caulerpa.
Dredging technology has already been proven to work at the bottom of the sandy sea, Crawford said.
“Now we’re just looking to put this technology on a machine that will be like a underwater tractor that can go GPS, 24 hours a day.”
Unlike the Great Barrier, exotic seaweed are still mainly at the bottom of the sea in the islands Bay area, Crawford said.
Finding out how to get rid of marijuana in rocky reefs would be important in the long run, he said.
Biosafety Pest Administration Director, New Zealand, John Walsh expected Dredging, UV and Chlorine Chamber to complete.
“We are very focused on understanding what are the widest impacts for us to have … a variety of tools that can be used in different locations in different conditions.”
The new technology would be developed over the next 6 weeks, Crawford said, and they expected to harvest Caulpera with her in early May.
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