Playing recordings of a healthy ocean can help restore marine ecosystems | Innovation

In 2016, Stephen Simpson, a marine biologist at the University of Bristol in England, returned to a study site off Australia’s Lizard Island, part of the Great Barrier Reef. Back-to-back cyclones that broke reefs and upset corals hit in 2014 and 2015, followed by a massive bleaching event in 2016, which devastated the coral ecosystem. After all that, “It was like swimming in a graveyard,” Simpson says.

Feeling “absolutely devastated,” Simpson and graduate student Timothy Gordon decided to channel their grief into action. In 2017, they piled up coral rubble to build dozens of new miniature reefs. They placed loudspeakers nearby to play recordings made when the reefs were healthy. Twice as many young fish settled on the reefs near these enclosures. “We found that we could actually start to rebuild the reef community,” Simpson says.

Simpson and Gordon’s project is just one of many research efforts showing that sound can be an essential tool in securing the future of the ocean. In a new article, Brittany Williams, a graduate student at the University of Adelaide in Australia, reviewed projects that used sound to help restore ecosystems, both in the ocean and on land, or that studied how sound attracts animals. “We wanted to try to spread the word that sound has great potential,” she says.

This potential stems from the fact that a healthy ocean is noisy: fish hiss and grunt, sea urchins scrape food off the seabed, dolphins screech and lobsters play their antennae like violins. Animals love all that noise. Like the hustle and bustle of a big city, the familiar din of a healthy habitat attracts young creatures in search of a forever home.

In some of these earlier experiments, scientists broadcast bird calls to attract seabirds, including arctic terns and marbled murres, to new nesting sites. In the ocean, researchers have found that sound is one of the cues baby fish use to find and settle on a coral reef after spending their first few weeks swimming in the open ocean. maybe the fish was hearing the way back,” Simpson says.

“The underwater acoustic world is essential to the survival of most animals,” Simpson says. “We’re starting to see the world from their perspective in a way that we don’t, really, see when we’re just swimming with our eyes open.”

Williams’ own research demonstrates the power of sound. In experiments started during her postgraduate degree in Australia, she investigated how sound can help oyster larvae choose where to settle. The tiny animals, barely big enough to spot without a microscope, have a little foot that “kind of wiggles” to help them reach their chosen spot, Williams says. “Then they stick to it and become the adult oyster, and they stay there forever.”

In the lab, Williams put oyster larvae in jars and played some of them a recording of an arid site where an oyster reef once stood. Other oysters played nothing, while a third group heard the sound of a restored reef crackling and jumping along with snapping shrimp. Larvae that heard the restored reef were about twice as likely as others to settle and settle on the bottom of the jar.

Seeing the difference, “I was like, wow, I almost can’t believe it!” said Williams. “I ran away and told my supervisors.” The results helped motivate Williams to pursue a doctorate and continue her research, she says. “It’s exciting to have a small role in uncovering all of this.”

Simpson is now experimenting in the Caribbean to see how sounds attract fish there. Williams began his own field experiments, playing reef sounds to attract oyster larvae. She hopes to find out which elements of the soundscape oysters prefer and whether it’s possible to attract oyster larvae without also drawing the fish that will eat them.

Simpson says audio playback is an exciting tool that could soon improve reef restoration projects in the wild. People are already rebuilding reefs and waiting for ocean life to populate them. Sound could speed up this process.

This article is taken from Hakai Magazine, an online publication on science and society in coastal ecosystems. Read more stories like this at hakaimagazine.com.

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