Young people don't want to grow up in degraded neighborhoods devoid of the life and color that mark a healthy ecosystem. And surprise, surprise, the same goes for young coral. That's a problem because, without new life coming in, established but ailing coral reefs risk "becoming ocean graveyards," joining half of the world's coral reefs lost since the 1950s, the Guardian reports. Thankfully, coral may be easier to trick than humans—with the equivalent of a boombox blasting some good tunes.
Previous research showed coral larvae swim toward the sound of healthy reefs, potentially sensed through hair-like appendages called cilia, so scientists tested whether playing the sounds of a healthy coral reef on underwater speakers could attract coral larvae to damaged areas, per ABC News. They installed speakers at two degraded and one healthy reef off St. John, the smallest of the US Virgin Islands, but played sounds of snapping shrimp and fish scraping on coral over three nights only at the degraded Salt Pond reef. They then watched to see if mustard hill coral larvae, sealed in containers of filtered sea water with artificial rocks, would be tempted to put down roots, so to speak, at all three locations when placed one, five, 10, and 30 meters from the speakers.
Wherever coral settle, they're fixed in that spot, so it's a decision not to be taken lightly. According to the study published Wednesday in Royal Society Open Science, 1.7 times more larvae settled at the Salt Pond reef on average than at the other two sites. As the settlement rates fell with distance from the speaker, researchers believe the recordings were key. More research is needed. "You don't want to encourage [larvae] to settle where they will die," notes lead study author Nadège Aoki, a PhD candidate in biological oceanography at MIT currently employed at the Woods Hole Oceanographic Institution. Still, the recordings could become part of "a multi-pronged effort" to save coral reefs, Aoki says. (More coral reefs stories.)