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The conservation effort returning lost seaweed to Sydney’s shores

After initial experiments showed crayweed was once again viable on the Sydney coast, transplants were established at sites including Malabar, Coogee, Little Bay, Freshwater and Bondi. Others are planned for Newport and Dee Why this year.

Crayweed at Cabbage Tree Bay on January 15.

Crayweed at Cabbage Tree Bay on January 15.Credit:Derrick Cruz

Adult plants are harvested from Wollongong and the Central Coast before they’re attached to underwater mats using special equipment to ensure the plants aren’t harmed.

The transplant isn’t like a tree, which can be moved from one yard to another, because the plants can’t establish new roots, also known as holdfasts. But the crayweed can reproduce.

Mr Cruz said: “It’s the next generation of crayweed plants we’re looking for.

Researcher Madelaine Langley measures a crayweed.

Researcher Madelaine Langley measures a crayweed.Credit:Derrick Cruz

The researchers were joined by the Herald this week as they checked and measured the baby crayweed about 30 metres north-west of the rock pools at Fairy Bower Beach, in an area frequented by swimmers and snorkellers.

The transplant was carried out in April 2019, and already some crayweed babies are up to 17 centimetres tall. Some of the distinctive green plants could be seen from the surface.

To reproduce, male and female crayweed have “underwater sex”, requiring sperm and eggs. Reproduction can be triggered by their removal and relocation by researchers.

The crayweed is about 30 metres from rock pools at Fairy Bower Beach.

The crayweed is about 30 metres from rock pools at Fairy Bower Beach.Credit:Kate Geraghty

“When we put them back in the water, they think death is imminent and they immediately reproduce,” Mr Cruz said.

“The day after we plant we notice the fish are frolicking in the crayweed, using it as habitat, [and] other species are eating it. The evidence is immediate really.”

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Once the population is established and self-sustaining, all infrastructure is removed and there’s no sign researchers were there. With every transplant, they are finessing their methods, including the best time of year to harvest the adult plants.

Ms Langley said one rewarding aspect of the project was getting the community engaged, including speaking to local swimmers, collaborating with a primary school and enlisting the help of volunteers when the crayweed was transplanted.

“We want people to engage with it and actually go and see it as well,” Ms Langley said. “The heart can’t love what it doesn’t know.”

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