Last updated April 30, 2018 at 4:11 pm
The symphony of the sea is being silenced.
A coral reef is a surprisingly loud place. From pistol shrimp that stun their prey with an extremely loud pop, to the territorial chirping of damselfish, to the pops and clicks of chattering clownfish, a healthy, thriving reef community is noisy. Baby fish looking for somewhere to live and breed use reef noise as a guide.
The Great Barrier Reef has suffered immense stresses in recent years, with massive coral bleaching events and damage from tropical cyclones.
Researchers wanted to see how this has changed the underwater soundscape. By analysing reef sounds on areas of the reef that have have been recently degraded, the research team found overall the reef was quieter and much less acoustically diverse when compared to measurements made five years earlier.
“It’s heartbreaking to hear,” says Tim Gordon, marine biologist at the University of Exeter.
“The usual pops, chirps, snaps and chatters of countless fish and invertebrates have disappeared. The symphony of the sea is being silenced,” he says.
The research team then set up artificial reefs and set up underwater loudspeakers to see which soundscapes young fish were attracted to. Would fish choose the healthy noisy reef sounds of the past, or the muted sounds found now on degraded parts of the reef?
They found that the degraded reef sounds attracted 40% fewer juvenile fish compared to previously healthy reefs.
“If fish aren’t hearing their way home anymore, that could be bad news for the recovery prospects of reefs,” says co-author Harry Harding from the University of Bristol
“Fish play critical roles on coral reefs, grazing away harmful algae and allowing coral to grow. A reef without fish is a reef that’s in trouble.”
The Great Barrier Reef is in all sorts of trouble, including large scale damage from coral bleaching events in 2016 and 2017 and ocean acidification. The resulting quieter environment attracting fewer fish makes it even more dififcult for reefs to recover quickly.
“If the reefs have gone quiet, then chances of the next generation of fish recolonizing the reefs are much reduced. Without fish, the reefs can’t recover,” says senior author Steve Simpson at the University of Exeter.
“Being able to hear the difference really drives home the fact that our coral reefs are being decimated. Some of the most beautiful places on Earth are dying due to human activity, and it is up to us to fix it” says Gordon.