Opening image: Simon Branigan dives the reef restoration project at Nine Foot Bank, inside Port Phillip Bay. The original shellfish reefs were decimated soon after European settlement. Photo Jarrod Boord


“Oh yeah! Check out these ones — they’re looking great!” Simon Branigan fishes a scallop shell out from a giant plastic tank and points to a cluster of tiny specks stuck on the fluted surface. To the untrained eye, they look like fossilised mud blobs. But Kim Weston leans in for a closeup look, gives them the big nod and an even bigger grin. The spat, baby oysters — that are being hatched right next to the slow ebbs and flows of Swan Bay in Victoria, down south on Wadawurrung Country — are doing just fine.


Over the past seven years, Simon, the Marine Restoration Lead for The Nature Conservancy Australia, and Kim, who manages the Victorian Shellfish Hatchery, have successfully produced more than 13 million native flat oysters — Ostrea angasi. But these little oysters aren’t destined for a fancy restaurant. Instead, they’ll be playing a critical role in the recovery of the great shellfish reefs of the south.


“Just picture a coral reef, a three-dimensional habitat growing in the ocean,” explains Simon. “But instead of coral, you've got oysters and mussels — the bivalve species — growing up from the seafloor. They cement together, they grow on top of each other and over time, increase in size. There’s other bivalves like scallops and abalone that also grow in great abundance, but they don’t form reef structures.”


Shellfish reefs do all kinds of lovely things for our oceans, estuaries and coastlines. Bivalves like oysters and mussels are filter feeders. They clean up dirty pollution and all kinds of contamination, including excessive nitrogen from agricultural runoff, which can cause algal blooms. They improve water clarity, which can encourage flowering plants like sea grasses to regrow, and they provide safe homes for a whole bunch of different fish species and invertebrates. They can also help to protect our coastlines from being damaged by erosion.


But the great tracts of shellfish reef that once covered the seabed right along the southern edge of the continent, have been lost or degraded to the point of collapse — they are now one of the most threatened marine ecosystems in Australia. Globally, more than 90 per cent of oyster reefs have been lost.


“For thousands of years traditional owners around the world have sustainably harvested shellfish,” says Simon. “When the European colonists first arrived here, the native oyster reefs in Port Phillip Bay, being subtidal [always covered in ocean water], were so expansive that they were a navigational hazard. They were that big and abundant.”


“But the Europeans decimated the shellfish reefs within a relatively short period of time. The first gold rush in Victoria was actually an oyster rush. People harvested them for food. A bunch of oyster bars opened up in Geelong and Melbourne. Whole oyster shells were also burnt in kilns to extract lime for building. This kind of thing was happening right across the country. A lot of the heritage buildings in Melbourne, Perth and Brisbane were built on the back of these shellfish reefs. They absolutely hammered them. And now we’ve got this intergenerational loss of knowledge — a lot of people don't realise that our bays and estuaries used to be full of oyster reefs.”


In 2015, Simon and his team set about changing that. The Nature Conservancy — which has been working on shellfish reef restoration projects in the United States for over 25 years — initiated a pilot reef building project, working in collaboration with fishers at the Albert Park Yachting and Angling Club, who had seen their local oyster reef slowly decline since the 1980s. It was the first time that anyone had a proper crack at restoring a shellfish reef in Australia.

Simon Branigan with a coconut fibre bag full of scallop shells recovered from local restaurants, which form the base of Port Phillip Bay’s new shellfish reefs. Photo Ula Majewski

“From the reconstruction process through to it being a living, breathing shellfish reef, it takes time — you’re looking at around five to eight years,” offers Simon. “This is very different to an artificial reef. What we’re doing is ecological restoration — we're aiming to recover the reef back to a natural state. In Port Phillip Bay, we don't have a remnant reef as such. The only remnant native flat oyster reefs that we know about are in Georges Bay [on the east coast of Lutruwita/Tasmania] and we’ve studied those to set some reasonable benchmarks for the recovery of reefs in Port Phillip Bay and elsewhere.

“We've been working hard to restore reefs back to their natural state, so being able to dive the old growth oyster reefs of Georges Bay and see shellfish reefs that have been there for thousands of years, to experience first-hand what we're aiming to achieve, was pretty special.”

Twelve hectares of reefs later in Port Phillip Bay, and there’s been a whole lot of success and a whole lot of learning — about spawning and hatching, transportation and marine construction. The unique sensitivities of local ecologies and the housing preferences of baby oysters. All the very practical (and critical) details of how to bring back a lost ecosystem — how to grow a thriving shellfish reef.

“We did some experimental trials with one of my good mates – Ben Cleveland – for his PhD at the University of Melbourne,” offers Simon. “As part of his research, he looked at the settlement preferences of Angasi oysters and basically found they love scallops. So that’s what we use.”

Kim Weston laughs and admits there’s been a few challenges along the way. “But we learn and we learn. At the start, we used plastic socks to house the scallop shells and spat while they were growing in the tanks. But we wanted to move away from plastic, for obvious reasons, so we sourced coir – coconut fibre – socks. But the first lot we trialled killed most of our oyster larvae. It was pretty bad. Then we figured out what had happened. The socks had been fumigated when they came through customs. So now we soak them for five weeks to make sure they’re really clean, and we’re getting some good results.”

Simon explains that there’s quite a few steps to restoring a shellfish reef. “The oysters spawn and the larvae swims around in the water column for a couple of weeks. They grow feet and they become what we call ‘sticky’. But to get to the next life stage, they need to settle on something to grow. That’s why you’ll see oysters and mussels on jetties. What we’ve lost is that oyster reef substrate — there’s nowhere for them to land on another oyster, to attach and to grow.

“So the first part of the restoration process is putting back the substrate. We contract a marine construction company with a big barge and a long reach excavator and we use two types of materials for the reef base — limestone rubble and recycled shells. At the same time we started restoring shellfish reefs, we also kicked off the ‘Shuck Don’t Chuck’ shell recycling project. Basically, we're reusing shells from seafood wholesalers, restaurants and craft beer bars. Our partners B-Alternative pick them up and deliver the shells to a curing site on the Bellarine Peninsula where they are weathered and quarantined for at least six months and then we use the shells and the limestone to create a new reef base, which vary in size but commonly are at least 150 square metres. We put those reef bases into the sea at the time of year when the wild oysters are spawning and we spread the juvenile oysters (or spat) onto scallop shells.”

Left: Scallop shells are seeded with oyster spat, which are grown out ready to be added to the new reefs. Photo Ula Majewski. Right: The golden kelp forests of Australia’s south have been hit hard by marine heatwaves and invasive predators, both threats driven by climate change.

Simon’s team will have restored 70 hectares of shellfish Australia-wide by mid-2023. It’s part of their national Reef Builder partnership with the Australian Government and through earlier work from the sub-tropical waters of the Noosa estuary on Kabi Kabi Country to the rugged southern oceans of Lutruwita/Tasmania and way out west across the Bight and over to Perth and Albany on Noongar Country.

“We’re working on Sea Country so engaging with First Nations communities and leaders has been critical at every step of the way. One of the great joyful moments of this project was being able to restore Sydney rock oyster reefs in Noosa estuary, which is one of the busiest in Australia. To be able to work with the local community and having the strong support of the Kabi Kabi people was really powerful.”

The Great Southern Reef zone – 8000km of coastline from Kalbarri in the west right across to northern NSW – has been a key geographical focus for much of this important restoration work, but the scope extends to other ecosystems beyond shellfish. The Nature Conservancy team are currently working with a brilliant bunch of individuals and organisations to restore golden kelp in Port Phillip Bay and compile a roadmap for the recovery of giant kelp forests across southern Australia.

The Great Southern Reef is an ecological wonderland still unknown to so many people. It’s home to an extraordinary array of marine species — leafy sea dragons, spotted wobbegongs, colourful nudibranchs and southern rock lobsters. This diverse saltwater community includes many endemic marine species, like the rare spotted hand fish, that are found nowhere else on earth. Whales, orcas and great white sharks make their great oceanic migrations through its deep blue waters and right along the reef, expansive forests of golden kelp sway gently in the swell. Legendary oceanographer, Dr Sylvia Earle recognised this unique marine ecosystem as a ‘Hope Spot’, one of those very special sites across the globe critical to the health of our oceans.

But the great golden kelp forests of the south are in trouble. “There are a lot of endemic species here and they all rely on a healthy kelp ecosystem functioning,” explains Dr Prue Francis, Senior Lecturer in Marine Science at Deakin University. “But right now, golden kelp is being lost right along the Great Southern Reef. We’ve seen the impacts of climate change that kelp is particularly susceptible to. We’ve seen heat waves off the coast of Western Australia, and here in Victoria we are seeing an influx of urchins that have overgrazed the kelp, especially in areas like Port Phillip Bay.”

“Without those healthy kelp forests along the Great Southern Reef zone, we’ll start to see a whole lot of knock-on effects that will impact the food chain and habitat,” says Prue. “We’ll see changes in the species richness and diversity that we currently have. This is clearly an ecological concern, but it will also have critical impacts for commercial fisheries targeting crayfish and other species, and for the tourism sector. Important commercial interests for local communities, as well as critical environmental and cultural values are at stake.”

Luckily, there’s a committed bunch of ocean lovers right across the country — big-hearted local communities, brilliant scientists, progressive seafood industry folk and all kinds of conservation practitioners — who are on the case.

Kaylah Gawne, a Marine Biology Honours student at Deakin University, is one of them. She’s working with Prue’s team at the Queenscliff Marine Science Centre to find better ways of cultivating golden kelp. Kaylah’s research is focused right on the start of the seaweed’s life cycle, growing sporophytes (tiny baby kelps) in a controlled lab experiment. Once they’re old enough, these minute specks of life — which show up on a microscope slide as something resembling a lurid green worm crossed with a miniature seahorse — will be transported to marine restoration sites in Port Phillip Bay and grow up into big frilly fronds of golden kelp.

It takes between five and eight years to bring a shellfish reef to life. Wilson Spit, Corio Bay. Photo Jarrod Boord

“I’m so excited about this project,” offers Kaylah. “It’s the first time this kind of research — in terms of kelp cultivation at the sporophyte level — has been done in Victoria. Hopefully, the results from my study can help with the future of seaweed cultivation and outplanting in Port Phillip Bay, and with marine restoration here and across the country.”

The ecological recovery of marine ecosystems across the Great Southern Reef zone is still, in many ways, in its infancy. But from little, tiny spats, big dreams of thriving oceans are already growing, at speed. “The big picture is full seascape restoration — looking at all the ecosystems used to be present and coming up with a plan,” says Simon Branigan.

“Right now, we’re working with our partners to kickstart restoration at scale for kelp, seagrass and other ecosystems. We’re also looking to restore shellfish reefs in 60 locations across Australia. We’ve put the case forward to government that shellfish reef restoration is very jobs intensive. If you really want to support regional communities, other than building hospitals or roads, you can invest in marine ecosystem restoration. We're in the business of restoring nature but if you can also create jobs at the same time, then it’s a win-win.”

Opening image: Simon Branigan dives the reef restoration project at Nine Foot Bank, inside Port Phillip Bay. The original shellfish reefs were decimated soon after European settlement. Photo Jarrod Boord


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