South Australians are encouraged to eat local oysters and donate the shells to help restore native reefs. These reefs can filter ocean water and fight harmful algal blooms. The program also involves sinking limestone lumps in the ocean with underwater speakers playing snapping shrimp sounds to attract baby oysters. Dr Dominic McAfee, marine ecologist at the University of Adelaide, said there used to be about 1,500 km of oyster reefs along South Australia's coast before colonisation. However, dredging made them “broken, forgotten, and functionally extinct.” A single oyster filters about 100 litres of water every day, so reefs greatly improve water quality. South Australia faced a severe toxic algal bloom that killed thousands of fish and marine animals. This event has been described as an underwater bushfire. A Senate inquiry recommended funding large-scale marine ecosystem restoration projects, including reef restoration along the SA coast. Dr McAfee explained the shell donation program lets the public take action amid eco-anxiety caused by the algal bloom. "People can enjoy eating beautiful SA oysters then recycle those shells to provide this biodegradable, natural substrate, which is what oysters historically used to build reefs," he said. The donated shells are cleaned, sterilised, and placed on the sea floor inside biodegradable cages. Baby oysters settle on these shells and produce a substance that cements the reef together. Using underwater speakers playing healthy reef sounds has shown to increase oyster numbers dramatically. Female oysters can release up to 3 million microscopic spats that float and look for places to live. Healthy reefs offer many nooks and crannies for small animals like snapping shrimp. Dr McAfee’s team created an 8-meter “oyster raceway” where playing crackling reef sounds attracted baby oysters. Lucy Hood, SA’s climate, environment, and water minister, said the government funds 25 community reefs using donated shells and four large limestone reefs. Building native oyster reefs improves water quality, restores sea grass, boosts biodiversity, and raises fish stocks. “Communities wanted to know how they can help,” Hood said. She called on people to eat SA oysters, mussels, and scallops, then dry and donate the shells for reefs. Another project partners with conservation group OzFish, where volunteers collect seagrass seeds to restore sea grass fields by planting them on the ocean floor. These efforts are part of a joint state and federal plan to help communities and industries recover from the bloom and continue research. The bloom's dominant algae species is Karenia cristata, which prefers cooler waters, raising hope it may not worsen in summer. Chlorophyll-a levels, which signal algae concentration, have dropped. Hood said she is “cautiously optimistic.” Those interested can join restoration projects or donate shells via the government’s algal bloom response website.