The noise of the ocean has changed and entire ecosystems are threatened

The soundscape of the great seas in the times of the Anthropocene: thus the underwater noise produced by men threatens over 150 species

Ocean: man-made noise threatens entire ecosystems
The soundscape of the oceans is changing: over 1.500 marine species at risk (Photo: Envato)

In the water, the sound travels faster and reaches further than other sources of information. Thus, over the course of evolution, it became a point of reference for many organisms, which began to use it to interact and interpret the marine environment.

From whales to small invertebrates, inoceano there are many who depend on the clarity of the soundscape marine. However, the sound of the Anthropocene ocean is very different from that of the pre-industrial age: i sounds produced by human activities are now predominant, and have a heavy impact on marine life.

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The noise of the Anthropocene: impact on at least 150 marine species
The noise of the oceans has changed a lot: where previously there were the sounds of animals and underwater volcanoes, today there is an increasingly cacophonous din (Photo: Envato)

Noise, son of man: impact on at least 150 marine species

The ocean has never been silent, on the contrary. Before the industrial revolution, however, the marine soundscape it was essentially made up of sounds coming from geological and biological sources: earthquakes, storms, underwater eruptions, songs and impulses of large cetaceans and small marine organisms.

In the ocean of the Anthropocene, the biophony has dropped dramatically due to the gradual disappearance of many "noisy" marine animals, while the levels of noise of anthropogenic origin they have doubled from decade to decade, starting from the XNUMXs.

"There is a lot of evidence that underwater noise pollution is a problem for many marine species: to date, impacts on at least 150 species have been documented”, explains the doctor Lindy Weilgart, author of the latest report published by the UN Convention on the Conservation of Migratory Species of Wild Animals (CMS).

Animals exposed to loud noises emitted by human activities, the report states, can suffer direct injuries and permanent changes to their hearing threshold, which compromises their ability to orient themselves and communicate. The noises produced by man can push entire populations away from their habitat, and cover important natural sounds, such as the call of a mate.

Uno studio published in the journal “Science” in 2021 showed that over the last 50 years maritime transport has caused a 32-fold increase in low frequency noise along the main maritime routes.

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Storm over the ocean, an important sound source
Wind noise, rain on the sea surface and currents are an integral part of the underwater soundscape (Photo: Envato)

The ocean soundscape in the Anthropocene is very different

As stated in the study cited, in the deep sea Sound travels faster and farther than other sensory signals, such as light or chemicals. Marine animals have developed a wide range of receptors for detecting sound, and this goes far beyond the kingdom of fish and cetaceans: even invertebrates, such as jellyfish, they receive sounds. The sound spectrum that falls within the sensory horizon of marine creatures is impressive: if reptiles can perceive sounds with a frequency lower than 5 kHz, large cetaceans detect sounds up to 200 kHz.

Ma how the noises have changed of the ocean in the Anthropocene era? Sounds of geological origin remain an important source, as do those linked to the climate: the wind blowing, the rain on the surface of the sea, the seasonal process of ice melting they are fundamental elements of marine soundscapes in different regions of the world.

Then there is the biophony: “Marine animals intentionally produce sounds ranging from infrasonic (<20 Hz) to ultrasonic (>20 kHz), although most are emitted between 10 Hz and 20 kHz and are audible to a wide range of taxa”, we read in the study. These are sounds that are also emitted in regular sequences ortime patterns”, as occurs in the melodious songs of whales, which show a certain interaction with the other natural sounds of the sea.

This thousand-year-old oceanic symphony, once dominated by the songs and tremors of underwater volcanoes, is seriously threatened by a cacophonous din of anthropic origin: Navigation, seismic exploration, military and industrial activities have an increasingly violent impact on the marine soundscape.

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The sounds of the ocean have changed
Most noises made by marine animals are found between 10 Hz and 20 kHz and are audible to a wide range of species (Photo: Envato)

The threat of noise does not only concern dolphins and whales…

Marine soundscapes are at the center of research conducted by Lucia Di Iorio, professor at the University of Perpignan leading investigations into Soundscape Oceanography & Ecoacoustics. Her task, in the context of international projects TREC and BiOcean5D, is that of record underwater sounds along the European coasts to better understand marine biodiversity and the impact of anthropogenic noise on organisms.

"Ship traffic compromises animal communication”, explains Di Iorio interviewed by Euronews. “It's as if you lived near a highway, or a busy road, with cars constantly passing by“. The researcher is working on the possible influence of underwater sounds on phytoplankton: the problem of noise pollution has always been underestimated, from this point of view. It is only in the last ten years that it has become clear that the threat goes far beyond whales and dolphins.

Several investigations have confirmed that the jellyfish, the crustaceans and coral reefs they are suffering from the noise produced by man: the problem affects the entire ecosystem, and is a concrete threat to be addressed as soon as possible.

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Jellyfish also suffer from excessive ocean noise
Ocean sound pollution doesn't just affect whales and dolphins: jellyfish, crustaceans and even coral reefs are suffering from the cacophony of human activities (Photo: Envato)

How to reduce ocean noise? Some of the solutions

The report of the United Nations Convention on the Conservation of Migratory Species of Wild Animals (CMS) for the first time aims to offer concrete solutions and practical guidance on best available technologies (BAT) and on best environmental practices (BEP) to reduce noise resulting from human activities underwater.

The document takes into consideration three of the main sources of noise pollution: the maritime transport, seismic surveys with compressed air weapons (used in oil and gas exploration) and piling, construction technique used for offshore wind farms and other marine infrastructure.

The most effective method to reduce the negative impacts of underwater noise on wildlife, the report states, is the application of silencing technologies. In some cases, these “silencing” practices can also be a contribution to climate change mitigation. An example above all is the so-called slow steaming, i.e. the reduction of the speed of merchant ships and container ships: silence the 10-15 percent of the noisiest ships would already be an effective solution, we read in the report, since these "contribute disproportionately to the overall noise generated by navigation”. Furthermore, by reducing the navigation speed, less fuel is consumed and produced less CO2 emissions.

Le seismic investigations with compressed air weapons they should be replaced by quieter alternatives, and even where it is not possible to embrace new technologies there are some mitigation measures of the damage that should be applied, for example, avoid carrying out these surveys in marine areas with high population intensity and carry out precise screening of aquatic life at least one or two years before the operations.

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Ocean: among the most dangerous noise sources according to the UN report are maritime transport, seismic investigations with compressed air weapons and piling, a construction technique used for offshore wind farms
Among the most dangerous noise sources according to the UN report are maritime transport, seismic investigations with compressed air weapons and piling, a construction technique used for offshore wind farms (Photo: Envato)