South Australians are being urged to feast on local oysters and then donate the shells to restore native reefs, which will filter ocean water and help fight harmful algae blooms.
The program will also feature submerged limestone reefs, with a soundtrack of shrimp blinking over underwater speakers to lure children’s shells.
Dr Dominic McAfee, a marine ecologist at the University of Adelaide, said there were about 1,500 km of oyster reefs along the SA coastline before colonisation, but dredging had left them “broken, forgotten and functionally extinct”.
A single oyster filters about 100 liters of water per day, so their rocks make a significant difference to water quality.
SA has been hit by a devastating toxic algae bloom that has left beaches littered with thousands of dead fish and marine animals, and has been compared to an underwater bushfire.
A Senate inquiry into Bloom recommended funding for “projects that provide large-scale, long-term marine ecosystem restoration and resilience, including meaningful reef restoration along the SA coastline”.
McAfee is working with the government on its reef restoration plans.
She said the seashell donation scheme is a way for the public – many of whom are suffering from environmental anxiety amid the ongoing devastation of algae blooms – to get involved and find agency and purpose.
“People can enjoy eating beautiful SA oysters and then recycle those shells to provide the biodegradable, natural substrate that oysters have historically used to build reefs,” he said.
“(The reefs) were all dislodged 200 years ago. We removed the rocks, the substrate, so now we collect the mussels, make sure they’re clean and sterile, and we put them on the sea floor and try to get the mussels to come and live on them.”
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The mussels will be kept in biodegradable cages. As baby oysters settle on them, they produce a substance that binds the rocks together.
McAfee said his team has shown that underwater speakers playing the sound of a healthy reef dramatically increase the number of oysters per meter.
Female oysters can release microscopic spits up to 3 meters long – baby oysters – which then migrate out in search of a place to live.
A healthy reef habitat has “lots of nooks and crannies” where small animals like snapping shrimp live, he said. His team built an eight-meter “oyster raceway” and played that raucous sound, and it attracted controversy.
State Minister for Climate, Environment and Water Lucy Hood said the government is funding the construction of 25 community reefs that will use donated shells and four massive limestone reefs.
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Creating wild and native oyster reefs filters water, creates healthy habitats, restores seagrass and promotes biodiversity and increases fish stocks, he said.
“You can’t stop these algal blooms from happening, but communities want to know how they can help,” he said.
“They feel a deep sense of sadness and sadness over the enormous loss of marine life and the impact on (their) pristine oceans as we navigate these difficult and unprecedented times.
“So we’ve launched a volunteer portal and people can see all the ways they can give back – so they can eat lots of oysters, mussels and scallops from SA, then we sunbathe them (to dry them and dehydrate them) and use them for community oyster reefs.”
Another project running with fishing conservation charity OzFish will involve volunteers collecting seagrass seeds, which are then sewn into hessian bags and dropped onto the seabed to restore seagrass beds.
The projects are part of a joint state and federal summer plan to help the community and industry recover from prosperity and for research and monitoring.
While it was initially thought that flowers were composed mostly of Karenia mikimotoi Species that prefer warm waters, testing has shown are the dominant species karenia cristataWhich prefers relatively cold water.
This has given some hope that the flowers will not deteriorate in the hotter months.
Hood said testing showed that levels of chlorophyll-a (which indicates the concentration of algae) had decreased, and said she was “cautiously optimistic”.
People who want to get involved in restoration projects or donate shells can visit the government’s algae bloom response website.
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