Underwater sound reinforcement – How artificial fish sounds could save coral reefs – Knowledge

Underwater sound reinforcement – How artificial fish noises could save coral reefs – Knowledge – SRF

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“Blubb”: Artificially generated reef noises can increase the colonization of coral larvae.

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Coral reefs are massively endangered. Now researchers have found a way to get them to grow again – with sound.

Corals don’t like silence. At least when it comes to the background noise in reefs: In healthy coral reefs, it is produced by fish and other marine animals. But as coral die-off increases due to climate change, overfishing and water pollution, the sounds are fading more and more.


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Corals belong to the group of cnidarians and consist of many tiny, invertebrates: the coral polyps. The polyps live in symbiosis with single-celled algae. Through photosynthesis, the algae produce oxygen and sugar, which the coral polyps utilize. In return, the coral polyps provide algae with a protected habitat and nutrients – just like a quarter of all plant and animal species in the sea. A delicate ecosystem, then.

Now researchers from the USA have found a promising solution: underwater speakers. The larvae of the coral-forming species “Porites astreoides” were exposed to artificial sound, which resulted in them settling on average 1.7 times (and up to seven times) more in the sound reefs than in locations without it.

The larvae usually orientate themselves on the sounds of the local sea creatures and decide where to settle. The more noise, the more promising the environment.

Not the first sound experiment

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Researchers at the English University of Exeter carried out a similar experiment in 2016: After one of the worst coral bleaching events in the Great Barrier Reef (when a third of the 2,300 kilometer long reef off Australia died in just a few weeks), researchers set up loudspeakers in some dead areas typical sounds from healthy reefs.

The researchers played the recordings for 40 days. With the result that more and more fish found themselves in the dead reefs. Because, like the larvae, they expected the pulsating life because of the music. Compared to areas that did not receive sound, twice as many young fish came to the reef. And they stayed. The stocks recovered within a few weeks.

The results of the new study by researchers at the “Woods Hole Oceanographic Institution” in Cambridge show: Not only fish, but also larvae react to the sounds and remain in the initially barren reef. The population of the larvae remained high even at a distance of 30 meters from the loudspeaker – in the experiment in the Great Barrier Reef it was only half as much.

However, sonication can only be one component, according to the researchers: “In addition, corals should be bred and released under controlled conditions.”

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