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Listen to the Sounds of a Dying Coral Reef

Healthy coral reefs produce a medley of sounds that ocean creatures use as homing beacons

A bleached coral reef (© Stephen Frink/CORBIS)
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Healthy coral reefs buzz with the gurgles, burps, swishes and groans of their marine residents. In fact, coral reefs are one of the noisiest ecosystems in the world, according to researchers from the University of Essex. Underwater microphones positioned miles away can pick up on their bustling cacophony. 

When a coral reef's health begins to declining, however, its noise also begins to fade. This is a problem for young fish and invertebrate larvae, which use the sound of the reef as navigational guidance after their birth in open water or their first tentative ventures further afield. When things go quiet, those young animals can lose their way—and their home. The University of Essex team found that young marine organisms' ability to detect the reefs declines by a factor of ten when the reefs aren't producing their usual level of noise. 

It's not just larvae that can hear the difference, however. Listen for yourself: 

See pictures of healthy and unhealthy reefs here:

A healthy reef system with soft corals and schooling anthias in the Maldives (© Michele Westmorland/Corbis)
A healthy reef with hard and soft corals in Taveui, Fiji (© Michele Westmorland/Corbis)
Bleached lettuce coral, killed by high ocean temperatures and other causes, in the Caribbean (© Norbert Wu/Minden Pictures/Corbis)
A staghorn coral colony with an extensive bleached area at its center in Kimbe Bay, Papua New Guinea (© Fred Bavendam/Minden Pictures/Corbis)
Bleached coral in the Maldives. The color in the coral is lost due to the expulsion of symbiotic unicellular algae called zooxanthellae that live within its tissues. Some of the coral here appears brown as it still contains the zooxanthellae, which is needed to provide the coral with nutrients and thus maintain its color. (© Georgette Douwma/ /Science Photo Library/Corbis)
A healthy Hawaiian reef colored by slate pencil sea urchins (© Dave Fleetham/ /Design Pics/Corbis)
A healthy, shallow hard coral reef off of Kadola Island in the Banda Sea, Indonesia (© Stuart Westmorland/Corbis)
Heat-stressed, bleached, branching corals in Misool, Raja Ampat, West Papua, Indonesia (© Jurgen Freund/Nature Picture Library/Corbis)
A healthy, Red Sea hard coral reef near Marsa Alam, Egypt (© Louise Murray/Robert Harding World Imagery/Corbis)
Shallow bleaching corals in New Ireland, Papua New Guinea (© Jurgen Freund/Nature Picture Library/Corbis)
A healthy coreal reef with soft corals and barrel sponges in Komodo National Park, Indonesia (© Jurgen Freund/Nature Picture Library/Corbis)
A healthy reef tiered with plate corals in Komodo National Park, Indonesia (© Jurgen Freund/Nature Picture Library/Corbis)
Hard corals show bleaching caused by heat stress in West Britain, Papua New Guinea (© Jurgen Freund/Nature Picture Library/Corbis)
Hard coral shows signs of bleaching due to increased water temperature in Misool, Raja Ampat, West Papua, Indonesia (© Jurgen Freund/Nature Picture Library/Corbis)
Hump coral—one healthy, at left, and the other badly bleached—in Lembeh Strait, Indonesia (© Fred Bavendam/Minden Pictures/Corbis)

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