Anyone who is discovering scuba diving for the first time comes away with this incredible feeling of having been weightless in the heart of a world apart.
Far from the din of the surface, here only the oxygen bubbles and your breathing rustle in your ears.
Welcome to the famous "world of silence" dear to Commander Cousteau.
But for dolphins, whales and their cousins in the family of marine mammals that inhabit the oceans, it's a whole different story.
They and their counterparts in the abyss suffer more and more from noise caused by human activities.
A real cacophony that can prove fatal and that even affects mollusks, spider crabs and other crabs.
This is what bioacoustician Michel André reveals on the occasion of World Whale Day this Friday.
“Underwater, noise propagates five times faster than in air, at a rate of 1.5 km per second, but cetaceans are not the only ones to suffer from noise pollution caused by maritime transport, offshore wind turbines or oil research, explains the director of the laboratory of applied bioacoustics at the Polytechnic University of Catalonia.
Marine invertebrates that have no ears like crustaceans, corals or jellyfish perceive vibrations and this causes massive acoustic trauma in them ”.
Mass stranding linked to military sonar ...
When the noise is too loud, Michel André affirms that some of these invertebrates “no longer have the ability to eat or orient themselves and that they can die in a few days”.
The phenomenon was already known to whales.
As early as 2002, scientists had for the first time recognized a causal link between the mass stranding of cuvier's beaked whales in the Bahamas, the Canaries, Greece, Italy or Spain and the use of military sonar in the sector. where the animals were.
“In the past, two blue whales were able to communicate when they were located in two different oceans,” explains Céline Sissler-Bienvenu, director of the protection association Ifaw France.
Today, the area in which they can get along has been reduced by 90% due to the noise generated by human activities ”.
"In 2001 and 2003, there were massive strandings of giant squids in Spain but no pathology explained their death" continues Michel André, who revealed that the phenomenon also affects invertebrates.
He ended up making the link with seismic campaigns to search for gas and oil carried out in the sector: "They used compressed air cannons to produce an acoustic load capable of crossing a water column of 3000 or 4000 m" .
Deafening maneuvers for the squid.
A cacophony of artificial sounds underwater
Today, almost all the oceans are affected by this noise pollution.
"The industrialization of the sea has continued to grow for more than half a century but it has been 80 years since we have ignored this cacophony of artificial sounds under water" sighs the scientist who pleads for the establishment in sea of ecological corridors "without noise".
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Winner of the Rolex Awards, Michel André created the first passive tracking system to avoid collisions with cetaceans.
He has since been at the origin of another project, called
Listen to the deep ocean Environment
.
In order to obtain the first global mapping of marine noise and its consequences, 22 underwater observation sites were distributed in all the oceans.
It emerges that the Channel is one of the most acoustically polluted regions of Europe, but also the Strait of Gibraltar and certain areas of Southeast Asia.
In this concert of decibels, France can be proud of having in the South Pacific an area where pollution is close to zero: French Polynesia which is not impacted by industrial activities.
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But even some "white" areas are on probation.
“The Arctic and Antarctica are the last two relatively unspoiled regions in the world,” underlines Michel André.
But as global warming melts the ice floes, oil exploration companies see new prospects for drilling and therefore installing off-shore platforms.
"New maritime routes could also open up to the circulation of cruise ships in Antarctica," warns Michel André.
However, these activities are a great threat to the biodiversity of the poles because of the noise they generate ”