Click, clack and pop: sounds indicate health of coral reefs, study finds

Monitoring the planet’s ailing coral is costly and arduous. Now new research shows that scientists can do it by listening in

The popping sound, like milk hitting puffed rice cereal, that you hear when putting your head underwater is not your ear adjusting to a different atmosphere – it is the sound of the submarine world. Fish chat to each other, or move water with their fins; hard-shelled creatures scrape against the surfaces; molluscs drag themselves to their nooks.

There’s more to these clicks, clacks and pops than just the tuneful wonder of it all. Oceanographers now say that monitoring the sounds of coral reefs can serve as a non-intrusive, inexpensive and efficient method for tracking the state of their health – and for planning better conservation interventions in the long run.

Scuba diver with a large school of yellow fish over a reef
A diver with a large school of bluestripe snappers over a healthy reef. Photograph: Design Pics/Alamy

New research shows that degraded coral communities do not sound as crackling and vibrant as healthy ones because thereduced biodiversity means less activity, so you can in effect judge the health of a reef by its decibel level.

“Soundscaping gives us this really nice heartbeat of what’s going on on the reef,” said Lauren Freeman, senior oceanographer at the Naval Undersea Warfare Center while presenting these findings to the Acoustical Society of America. “And our coral reefs are under quite a bit of duress from overfishing, from pollution [and] from climate change.”

Freeman and her team monitored acoustics in reefs off Hawaii between 2019 and 2020, comparing them to soundscapes from the ocean near Bermuda and New England. They immersed underwater microphones for up to six months and recorded soundscapes at intervals.

Coral growing on a fishing line
Coral growing on abandoned fishing line off Hawaii. Reefs are under pressure from overfishing as well as pollution and climate change. Photograph: David Fleetham/Alamy

By breaking down the resulting sounds and analysing it by the microsecond, they attempted to reconstruct what was happening underwater: different fish species feeding, whales passing by, boat engines roaring in the distance.

Most reefs are full of noise when it is warmer, and immediately before the sun sets and rises. Hotter weather tends to correlate with moments of greater activity among ecosystems –– many species give birth in spring, for example –– while dusk and dawn represent a sort of underwater “rush hour” between diurnal and nocturnal creatures, said Freeman.

Unhealthy coral communities sound less vibrant and also emit more high-frequency sounds, the researchers found. While healthy reefs give readings 0f 2-8 kilohertz, less diverse reefs tend to be above 12kHz, as they become overpopulated with macroalgae, which create bubbles of oxygen that float to the surface and pop, making a specific high-frequency sound.

The findings will help more researchers use soundscapes to study reefs, –and to monitor the progress of restoration projects already under way. Traditional surveying of reefs presents many challenges: expenses for boats and crews, time limitations for divers underwater, the small areas of reef that can be covered, and the fact that there are simply too many reefs to monitor. Sound surveys could change all that.

Katey Lesneski, director of restoration science at Coral Vita, a land-based coral farm for reef restoration, was not involved in the study but said more research would be needed to characterise what a healthy reef sounds like in different regions of the world.

It did, however, show promise. “This type of data collection has the potential to be highly cost-effective, cover a large area and be a constant source of information, as opposed to intermittent diving surveys,” she said.


Sofia Quaglia

The GuardianTramp

Related Content

Article image
Nobel-winning stock market theory used to help save coral reefs
Portfolio selection rules on evaluating risk used to pick 50 reefs as ‘arks’ best able to survive climate crisis and revive coral elsewhere

Karen McVeigh

28, Nov, 2021 @3:00 PM

Article image
Coral reefs crucial to origin of new marine species, finds study
New research provides a new incentive to protect reefs, overturning ideas that coral sealife originated elsewhere

David Adam, environment correspondent

07, Jan, 2010 @7:00 PM

Article image
Highly contagious marine epidemic rips through Caribbean’s coral reefs
Frustration among scientists as many islands, hard hit by Covid and hurricanes, struggle to fight stony coral tissue loss disease

CJ Clouse

23, Apr, 2022 @9:00 AM

Article image
Deadly coral disease sweeping Caribbean linked to water from ships
Researchers find ‘significant relationship’ between stony coral tissue loss disease and nearby shipping

Jewel Fraser in Port-of-Spain, Trinidad

22, Jul, 2021 @6:00 AM

Article image
Scientists discover ‘world’s largest’ seagrass forest – by strapping cameras to sharks
New study, carried out using tiger sharks in the Bahamas, extends total known global seagrass coverage by more than 40%

Laura Paddison

05, Nov, 2022 @8:00 AM

Article image
Reef ball burials: the new trend for becoming ‘coral’ when you die
Do underwater cremation memorials help people regenerate marine habitats in death or are they a ‘greenwashing’ gimmick?

Abby Young-Powell

21, Feb, 2022 @7:45 AM

Article image
Discovered in the deep: the rainbow fish that’s born female and becomes male
Scientists in the Maldives were only able to reach the rose-veiled fairy wrasse by using specialised diving gear

Helen Scales

19, Oct, 2022 @5:00 AM

Article image
Conservationists unveil plans to save coral from extinction

The Edge Coral Reefs project, led by ZSL scientists, has identified 10 of the most at-risk coral species for protection

Alok Jha, science correspondent

11, Jan, 2011 @6:01 AM

Article image
A starfish is born: hope for key species hit by gruesome disease
US team succeeds in captive breeding of sunflower sea stars and aims to reintroduce them to the wild

Laura Paddison

15, May, 2021 @7:00 AM

Article image
Biorock giving new life to coral reefs | Johnny Langenheim
Johnny Langenheim explains how an innovative method is sustaining corals and why on World Oceans Day we need to pledge for more such projects

Johnny Langenheim

08, Jun, 2012 @7:00 AM