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Sydney, Australia
CNN
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Clayweed, a large golden brown seaweed discovered along Australia’s southeast coast, plays an important role in ocean health. Its underwater forests capture carbon, create shelters for marine species, and serve as a nursery for creatures such as Avalons and Rock Lobsters.
According to Operation Clayweed, it became widely popular along Sydney’s coastline, disappearing from a 70-kilometer stretch around the 1980s when sewage was discharged into the ocean. The conservation initiative, run primarily by scientists from universities and research institutes, aims to restore 60 hectares of forest in shallow, rocky reef habitat.
“Dr. Adriana Verge, professor of marine ecology at the University of Sydney, New South Wales and co-founder of Operation Clayweed, said:
The group says improved sewage disposal means that the water around Sydney is clean enough to support clayweed, but for it to return, it must be successfully replicated after being planted first.
At designated repair sites, scientists and volunteers attach healthy male and female clayweeds collected from wild populations to biodegradable mats fixed to the coral reef.
Clayweed is reproduced when a male plant releases sperm into the water. This causes the eggs to fertilize from female plants. These fertilized eggs grow into young clayweeds known as “crabees,” anchored to the seabed and grown into new forests.
Once established, the mat is removed and the forest continues to grow and spread on its own.
Since its inception more than a decade ago, Operation Clayweed has targeted 16 sites along Sydney’s coral reefs, seven of which have established independent clayweed populations. The restored forest is covered with two hectares, and according to Vergés, microscope animals have already returned.
Three new sites, Lurline Bay, Dee Why, and South Maroubra, were added in 2024. Dee jumped from just 10 clayweed plants to 466 boy clayweeds in one year, by early 2025, with over 1,500 clayweeds established in South Marl Bra.
“I get a real kick from seeing it, and now it’s so expanded that you can even see it on the water,” says Vergés. “When the tide is low, you can see the clayweed shaking as the water is pulled away from the shore.”
The team plans to restore 10 more sites over the next two and a half years.
Dr. Prue Francis, a senior lecturer in marine science at Deakin University who is not part of Operation Clayweed, says the project could have a greater impact in the region.
“People often focus on dramatic bleaching of coral reefs, but in kelp forests, decay is quiet until it’s too late. These underwater forests support the entire ecosystem.
“Repair efforts like Operation Clayweed are not only about retrieving seaweed, but also saving the entire net of life that depends on it,” she added.
In addition to planting clayweeds, the team is using advanced technology to survive in a world where climate change warms the ocean and makes environmental conditions even more extreme.
that Genetic populations fed from the north and south of Sydney allow the restored population to reflect the natural genetic diversity and structure (the “critical innovation”) of healthy existing populations, testing whether clayweed genetics and their microorganisms (the small living creatures that live on the surface) play a role in withstanding elevated ocean temperatures.
The team is also considering accidentally building a “biobank” of clayweed population in case it’s wiped out by a heat wave.
“In Western Australia, such marine heat waves have erased an entire clayweed population. To prevent similar losses, we are turning to cryopreservation,” says Vergés. “We collect sperm and eggs from different populations and freeze them at ultra-cold temperatures.”
Other kelp species are frozen in laboratories around the world, but no one has successfully applied it to clayweed, Catalina Lopez Bermudes, who is working on a freeze effort as part of a PhD at the University of Sydney.
“There are no genotypes or biobanks for these species,” she explained. “So, when we lose our population, it disappears forever.”
Beyond technology Challenge, this work has deeper meaning to Lopez Bermudes. “It can be difficult as a young scientist to not feel hopeless, but this feels like something realistic, something that can make a difference,” she says. “It gives you hope.”
The effort Operation Clayweed is part of a wider global effort to restore lost kelp habitat. Kelp Forest Challenge aims to recover 4 By 2040, million hectares of kelp from around the world.
For Vergés, the success of the project is both scientific and personal. “I’m swimming in the ocean over the weekend, and wherever I go now, I can see Clayweed again,” she says.
