|Australian flat oysters. 📸: Cayne Layton.|
The extent and health of Australia’s native oyster reefs today are only at a fraction of what they were historically. Dredging, overharvesting, water pollution and disease decimated their populations, and with no substrate left on the seafloor for them to attach to, they never recovered (See here for more). As we enter the ‘Decade on Ecosystem Restoration’ we are making large commitments, yet marine restoration practice lags behind our ambition.
Oyster reef restoration projects are occurring worldwide to bring back lost reefs and return their health and function. In South Australia, Australia’s native flat oyster (Ostrea angasi) is being restored to coastal waters. But the current practice of relying upon the natural recruitment of oysters to boulder reefs carries a high risk of recruitment and project failure. At the University of Adelaide, a team of post graduate students are working with Professor Sean Connell and Dr Dominic McAfee to find ways to boost the recruitment of baby oysters to reefs and help safeguard restoration outcomes. My research focus is on how we may be able to build ‘highways of sound’ that artificially enhance marine soundscapes so that baby oysters settle onto our restoration reefs.
What is a soundscape?The underwater world has its own orchestra made up of a myriad of sources. Mammals like the manatee can chirp, squeak and squeal, whales and dolphins can click, whistle, moan and groan, whilst seals announce a broad vocabulary of barks, grunts, buzzes and trills. Snapping shrimp snap, sea urchins rasp, and fish can make many sounds from grunts, growls, barks and honks, to croaks, whistles, drums and pops. These sounds, alongside those from things like wind, waves, rain and shipping, are what we collectively call a ‘soundscape’. Habitats that have loud, healthy soundscapes filled with this biological orchestra are likely to attract marine life, because they are more complex, healthy places that can make good homes for organisms.
My Research:My research involves investigating whether we can use underwater soundscapes to boost restoration of Australia’s native flat oyster. Focussing on South Australian restoration reefs, I have been conducting lab-based and field-based experiments where I play sound to oyster babies using underwater loudspeakers. I want to see whether the babies prefer certain ‘soundscapes’ over others, how they react to the sounds (i.e. swimming patterns) and how they actually detect these sounds (is it the statocyst organ, fine hairs, something else?). The sounds we have been focussing on are those produced by the snapping shrimp, which is a loud crackling sound. We have been playing these sounds at a low cost across a wide spatial scale using speaker technology (‘SCUSU’: self-contained underwater speaker unit) developed by AusOcean. Currently, we are working at Windara Reef, Glenelg Reef and the Inner harbour of Port River to explore the role that sound plays during oyster settlement.
We have many questions to answer on how oysters, sound and restoration go together, but we hope our research can help boost the restoration of Australia’s oyster reefs.
By PhD student Brittany Williams from the University of Adelaide. For more updates follow her on twitter @0ysterWhisperer
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