Once Lost, Now Returned
Sydney of the early ‘80s had a lot going for it. Tom Carroll taking back-to-back surf titles, Reg Mombassa juggling guitars and canvases, a newly pedestrainised civic heart… Yet the city’s sewerage was spewing out onto its iconic beaches.
Rank drainage outlets had been emptying stormwater and, in some locations, the excrement of a burgeoning population into the shallows. By ’89 Sydneysiders, themselves, had been tipped over the edge. A quarter-of-a-million locals, travellers and one characteristically curt Angry Anderson rallied at Bondi Beach for the ‘Turn Back The Tide’ concert. The protest was heeded by the local government, with several outfall pipes being diverted to secondary treatment plants and extended further offshore. But, in one respect, the damage had already been done. From Kurnell to Avalon, once sprawling underwater forests of crayweed had been decimated.
A lone, detached crayweed plant has little chance of reproducing. Photo: John Turnbull.
It took decades to make the alarming discovery, with scientists establishing that crayweed (Phyllospora comosa) had gone extinct along Metropolitan Sydney’s subtidal rocky reefs sometime in the early 70s to 80s. This species of seaweed is a vitally important habitat former, especially if you like eastern rock lobster and abalone. It also contributes to detritus, a staple underpinning the food webs of fish like mulloway and bream.
Though public outcry had led to improved waste-water management, and as a result water quality, the crayweed did not return. That is, until 2011, when a group of leading marine scientists at the Sydney Institute of Marine Science sprung to action. They launched Operation Crayweed to restore the lost underwater landscape.
Lead marine ecologist Dr. Adriana Vergés measuring transplanted crayweed, which has flourished. Photo: John Turnbull.
The Operation’s early experiments showed that crayweed transplanted from thriving populations both north and south of the city onto temporary underwater mats, could not only survive, but also reproduce. “This particular species has a very similar life cycle to us humans; there are separate male and female individuals, and they need to release their eggs and sperm at the same time for reproduction to occur, which is impossible when the population has died out so significantly,” explains lead marine ecologist Dr. Adriana Vergés.
“The process of transplanting, it actually stresses the crayweed enough to the point where the first thing the crayweed individuals do when they are submerged in their new habitat is release reproductive gametes, a ‘let’s see if the next generation can get through this!’ approach”. With the first temporary mats fitted in 2011, her team started to see crayweed babies (craybies) beside their parent plants around six months later. For all chaperones involved, it was an “unbeatable” sight.
Affixing the temporary matting to reef, which is typically done at three metres depth. Photo: John Turnbull.
Lead scientist Dr. Ziggy Marzinelli anchors in male and female crayweed plants, with the hope of them spawning ‘craybies’ in around six months. Photo credit: John Turnbull.
From Malabar to Little Bay, Coogee, Bondi, Freshwater and Newport, the Operation Crayweed crew have tackled one stretch of coastline at a time. Though they never would have thought it possible in the early days, with these locations flourishing, their plan now is to re-establish healthy forests of crayweed along the entire Sydney Metropolitan area. “The goal here is for crayweed to return as a self-sustaining population, with multiple generations growing and extending outward,” tells Dr. Vergés. “We only need to provide that first push, give nature a helping hand”.
The Operation Crayweed team with Patagonia Manly's Emily Scroope. Photo: Adriana Vergés.
The Operation finds its strength among beach-loving locals, with volunteers pitching in to help plant and monitor restored forests as well as raise awareness. The core team has also recently been able to expand with a second project, rehabilitating endangered seagrass Posidonia in Port Stephens, thanks to keen citizen scientists.
“When they cut down our trees for tram lines, people in Sydney became really vocal, but with the underwater reefs, these remain sadly ‘out of sight, out of mind' to many,” says Dr. Vergés. She stresses the crucial connection between the underwater world and our terrestrial way of life. Sydneysiders and all humans depend upon healthy fisheries for food, thriving coastlines for protection as well as play, and underwater forests to draw down carbon amid accelerating global warming.
Restoring marine ecosystems and farming seaweed have been floated as potential mitigations to the climate crisis, with innovative projects underway. Fortunately, crayweed is not currently at the edge of its temperature tolerance in Sydney, unlike the vanishing giant kelp forests down south in Tasmania. Still, Operation Crayweed want their work to live on. They have started to look at the crayweed’s genetic makeup for signs of warmer-water-adapted genotypes, so these may begin to be introduced if need be.
Crayweed, far right, is crucial to coastal ecosystems, as a habitat for crayfish as well as abalone and several fish species. Photo: John Turnbull.
While the demise of metropolitan Sydney’s crayweed may have gone by unnoticed at first, its present-day regeneration is plain for all to see – even on Google Earth. “A really powerful aspect of our project is that it’s about helping the environment recover, and we would haven’t been able to succeed if the government hadn’t been pushed to tackle the water-pollution issue,” Dr. Vergés adds. “People can get really despondent or overwhelmed by the magnitude of environmental issues, I think that if we can share the stories of the solutions we’ve been able to achieve, it will inspire people to tackle more problems. Yes, there are lots of them. But in many instances, things are beginning to change.”
Banner image – Healthy re-generated crayweed forests at low-tide. Photo: Justin Gilligan.