Imagine you’re in a food court and spoilt for choice. How will you choose where to eat? It might be the look of the food, the smell, or even the chatter of satisfied customers. Marine animals do the same thing when choosing a good place to live. Once we understand these cues, we can use them to help nature recover faster than it would on its own. It worked as a charm for baby oyster reefs which were lured by amplified sound cues.
Natural restoration Of Reefs
Oyster reef restoration is gaining momentum in Australia and globally as a way to restore healthy ecosystems. Reefs of shellfish filter and clean vast volumes of water as they feed, while their shell piles provide habitat for fish. Oysters are also food for many marine species. When we try to restore these reefs, however, we hit a problem. Free-swimming baby oysters need to find the boulders dropped onto sandy seafloors at the restoration sites.
That’s where the siren songs come in. Many marine animals use sound like we use sight on land. Think of whalesong, which lets whales communicate over long distances. Sound is more useful than sight or smell underwater because it can carry information a long way and without getting pushed about by ocean currents.
As you float over the reef, you hear a cacophony of sound: crackles and pops from fish as they feed and invertebrates like snapping shrimp. If this soundscape is present, it tells oyster larvae it’s a healthy habitat. And because sound travels so well, the soundscapes are broadcast a decent distance. The songs attracted up to 17,000 more oysters per square meter to the restoration sites. Not only that, but over the next five months, close to four times more large oysters grew in the test areas, which accelerated habitat growth.
Can Oysters Even Hear?
The way we hear is based on the pressure of soundwaves hitting our eardrums. Marine mammals like seals and dolphins hear this way too. But fish and marine invertebrates such as oysters are different. Oyster larvae are brainless and earless, but they are certainly not clueless. Like fish, they hear by detecting and interpreting the movement of water particles stirred up by soundwaves as they pass. Soundwaves alternately squish and stretch water particles, sending vibrations in the direction the soundwave is moving.
Despite being only the width of a human hair themselves, larval oysters use these organs to follow these vibrations back towards the healthy reef producing the sound.
Novel Method
Researchers and community groups around the world are launching restoration efforts to repair some of the damage. In Queensland, for instance, fishing communities in Moreton Bay offshore from Brisbane plan to restore 100 hectares of oyster reef over the next decade.
This technique – and others like it – could help improve how many baby oysters or other keystone species actually make it to their new homes and start the great task of reef-building. In science, there’s no such thing as a silver bullet and there are potential downsides. But if we do this carefully, these techniques could help re-establish the invisible acoustic highways of the sea.
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Source: TheConversation
