| This week, my colleague Derek Hawkins reported on a fascinating experiment that took place on Australia's Great Barrier Reef. There, rising ocean temperatures have stressed coral — at bleached reefs, the coral animals have ejected the algae they need to survive. If the afflicted coral die, other animals vacate the area, leaving behind an emptier ecosystem. It's quieter, too. Fish make more noise than you might expect: They grunt, croak and sing. (The songs of the planet's loudest fish, who live near Mexico, rival the decibel levels of lawn mowers.) Shrimp, as scientists told Hawkins, pop their claws. In the new study, researchers lowered loudspeakers to the dead reefs and played recordings of healthy reefs. Drawn in by the sounds, the scientists report, local species diversity shot up by 50 percent. It's a clear, if unusual, example of the way sound influences wild animals. A large body of work shows that human noise is harmful to certain species: Noise pollution causes stress hormones to spike in birds. Mountain lions fled from the sounds of Glenn Beck, Rachel Maddow and other human voices tested in a 2017 study. (Croaking frogs bothered the big cats less.) The cacophony of civilization has reached the depths of U.S. national parks. But beneficial sounds flip the script. For years, researchers have explored "acoustic enrichment" for captive animals, like playing bird sounds for zoo leopards. Sounds played in the wild, this study suggests, may hold promise. The fish and crustaceans that followed the sounds stayed there, the scientists said. A richer soundscape can't save the coral by itself, but the presence of fish may help coral regrow. Toothy parrotfish, for instance, will snack on the microbial muck that sprouts on damaged reefs. |
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