“It can have significant impacts”: at sea, pollution is also noisy and it is because of human activity

The famous documentary film “The World of Silence”, which popularized the explorer Jacques-Yves Cousteau in 1956, has long led people to believe that the underwater universe is a planet without noise. Wrongly. Although the human ear cannot perceive everything once submerged, various studies have demonstrated that water represents an excellent medium for sound propagation.“They also emphasize (and above all) the importance of the sound factor for a multitude of marine species“, described Thomas Uboldi, from the European University Institute of the Sea.

In particular, he described, in various scientific articles, the buzzing sounds produced by male lobsters. “thanks to the vibration of their carcass“ to impress their opponent; species of molluscs that perceive the acoustic landscape around them “in order to synchronize their seasonal spawning and thus increase the chances of fertilization“ ; la communication “more than 2,000 km away“ cetaceans. This biophony, which brings together the sounds emitted by living beings, is very important for mobile marine species whose vision is limited due to low visibility.

But this beautiful ecosystem today seems disrupted.“When we talk about the pressures on marine biodiversity, we readily cite global warming, trawling, plastic pollution, etc. But noise pollution, much less known, adds to these pressures and can in certain cases have significant impacts.“, confirms Simon Popy, president of France Nature Environnement Occitanie-Mediterranean (FNE Ocmed).

Anthropophonie

So, in the wake of the United Nations Ocean Conference 2025 which officially launched, in Nice, the “high ambition coalition for a silent ocean“, the association decided to publish his mini-guide on underwater noise pollutionto act as an pedagogy. With a little humor, but a lot of seriousness, “because the uses of the sea, a source of noise, are all growing, notably maritime traffic, energy production, or military uses“, explains Simon Popy.

The guide thus describes all anthropophony, that is to say the sound generated by man in the marine environment through his activities. Thus, large and small vessels, like any other motorized water vehicle, produce sound by “Propeller cavitation, engine noise and water flow on the hull“. Oil or gas exploration disrupts the sound environment by “compressed air cannons used to measure the echo returned by the seabed“. Such as pile driving, turbine operation or ore extraction for industrial construction activities. Military activities also, through shooting exercises or sonars, can be harmful to wildlife.

“Rare are the places in the sea where anthropophony is absent, including in places with little human activity, maritime traffic generating low frequencies traveling over very long distances.“specifies the FNE Ocmed study. Which identifies four types of impacts on underwater fauna: “acoustic masking, i.e. sound interferes with communication between individuals and prevents the location of prey; behavioral change, which results in the adoption of a new migratory route, the abandonment of a habitat or the cessation of social and dietary interactions; physiological effects, with increased stress, slowed growth or increased respiratory rate; physical injuries, such as decreased hearing or organ damage that could lead to the death of the animal“.

Stranding of cetaceans, disturbed groupers…

A recent study has thus proven a very strong statistical correlation between massive strandings of cetaceans in the Mediterranean and the repetition of sonar exercises by the military. Another established that within the Cerbère-Banyuls marine reserve, the vocal behavior of the brown grouper and the corb differs in areas subject to high noise pollution, with a virtual disappearance of vocalizations attributed to reproduction. Still on our coast, blue and white dolphins approach the coastal shallows at night and move away during the day, “when human activities are most important“.

Ways to act

This noise pollution is all the more significant in the Mediterranean as the basin is closed, which reverberates sounds, and as it accommodates 25% of global maritime traffic. There are also numerous projects to build offshore wind turbines. “With, however, several methods of reducing the noise impact. The pilot farms have even set up observers to warn of the presence of cetaceans near the construction sites in order, if necessary, to temporarily stop the work.“.

Simon Popy and FNE Ocmed see this as the expression of awareness. But they insist that it is imperative to act, proposing to modify the shape of the propellers to limit cavitation, to isolate the noise of the machines, to lower the speed of ships by 10% – “ which would reduce noise pollution by 40% and, at the same time, greenhouse gas emissions by 13%.“ – or to implement reduced port taxes for the quietest boats. A win-win for everyone. On and under water.