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Sea weed attached to a rock underwater.
Photography: Supplied | Operation Crayweed | Olympus Digital Camera

GOOD NEWS: Operation Crayweed is restoring Sydney's underwater forests

This project is helping to restore a vital marine plant that went missing from Sydney's coastline in the '80s

Alice Ellis
Written by
Alice Ellis

Ever heard of crayweed? Probably not, since this type of seaweed – which used to play an important role in Sydney’s underwater eco-system – went MIA from our urban coastline decades ago. But fear not, this is a good news story: because Operation Crayweed is working to restore Sydney’s lost underwater forests.

First up, here’s a turbo tutorial on Sydney’s marine history… Sewage waste that polluted beaches in the 1980s meant the water quality of Sydney’s beaches was (literally) garbage, and crayweed populations carked it. Despite improvements in Sydney’s sewage systems by the ’90s, the damage had already been done – sampling done in 2008 revealed that crayweed had completely disappeared along a 70km stretch of Sydney’s coastline, all the way from Cronulla to Palm Beach. Pretty cray, considering seaweed is the habitat and food for hundreds of species of sea creatures, as well as capturing carbon and producing oxygen – much like trees on land.

So things were looking grim under water – until Operation Crayweed, a project by the Sydney Institute of Marine Science (SIMS), came about. In 2012, crayweed rejuvenation techniques were trialled in Long Bay, and there were almost immediate sea-changing results. 

The researchers basically facilitate seaweed sex – they take adult male and female crayweed, attach both to biodegradable mesh mats, then fix the mats on rocky reefs. They found the crayweed reproduces quickly, creating baby crayweed that attaches to the rock, creating the self-sustaining rebirth of crayweed forests. This results in other marine flora and fauna to repopulate, including golden kelp and creatures that live in weed. Winning. 

Breen Resources, a waste management and disposal centre, discovered Operation Crayweed through SIMS back in 2018, and decided to fund the project in Kurnell (the area at the southern headland of Kamay Botany Bay National Park, near Cronulla). The results of Operation Crayweed at Kurnell have been nothing short of cray-mazing. Today, researchers can see growth in crayweed up to hundreds of metres away from the Kurnell restoration site. 

Crayweed plantings have also taken place at other Sydney spots, including Bondi Beach and the Cabbage Tree Bay Aquatic Reserve in Manly, which was designated as a sanctuary zone in 2002 (i.e. no fishing allowed).

In the next three to five years, Operation Crayweed hopes to restore that whole 70km stretch of lost crayweed, helping to restore marine biodiversity along Sydney metro’s entire coastline.

To find out more about Operation Crayweed, and even ‘donate an underwater tree’, click here

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