How noise pollution threatens ocean life | The Economist

published on July 2, 2020

The ocean is often thought of as a silent wilderness

But under the surface is a symphony of sound

Sound that marine creatures rely on for their survival

to find food, to communicate, to navigate

The light vanishes metres below the surface

so the sound is really what supports life in water

But humans are increasingly polluting the ocean with noise

which is posing a threat to creatures, from the smallest to the most majestic

Now we are facing a global issue that affects thousands of species

This man is at the forefront of the science of ocean sound

He is working to dial down the volume

in a bid to protect marine life around the world

You can actually put it into the water

In his lab in Barcelona, Michel André is conducting an experiment

with an artificial ear

So this is our hydrophone, which is the artificial ear

that is able to capture all the sounds that will send them to our

artificial brain of electronics that is inside this housing

The underwater microphone is being put through its paces

before it is dropped into the Mediterranean Sea

The device is part of an ambitious experiment to better understand

how human sound is affecting marine life

Our perception of sound in the ocean is biased

Our ear is not made to listen underwater, our ear is made to listen in air

So for years and years and years, we really thought that

the sea was a world of silence

Michel’s team is carrying out

the biggest ever sound survey of the world’s ocean

Dropping hydrophones in multiple locations and at various depths

This combination of artificial ear, artificial brain plus transmission

is something that has given us, as human beings

a sixth sense that we didn’t have and now we can listen in to the ocean

as if we were dolphins, but also we can be anywhere

Sound is essential to marine life

because light doesn’t travel further than a few hundred metres underwater

Thousands of species use it to communicate, to find their way around

to spot their next meal or ensure they’re not someone else’s

It is a harmony of sounds that lived there for millions of years

Then, as human beings, we started to introduce

different sound, artificial sounds, through our activities only 100 years ago

So this is really recent that we have started to invade with our sound

Noise pollution is now recognised as a major threat to ocean life

Everything that we do in the ocean introduces sound

that may have an effect on the environment

There are more than 50,000 container ships

that sail everyday around the world

Unlike many other threats to the ocean, noise pollution is invisible

which means it’s often overlooked

But in 2002 the world started to take notice

14 beaked whales stranded on the holiday beaches

of Lanzarote and Fuerteventura

It was later discovered that multiple ships and submarines

were operating in the area using sonar

pulses of sound used to detect objects underwater

This is the first time that we could associate as

the cause-to-effect relationship that a noise introduced by the

navy sonar was leading to the stranding of these whales

Whales talk to each other through a complex language of clicks and whistles

These sounds help them to navigate and communicate

Man-made noises like sonar can disrupt this communication

and disorientate them

We know how sensitive people are to whales and dolphins, totem animals

and we’re seeing them washed on shore

by this human activity for the first time

This really helped understanding that this noise could have a detrimental effect

Since this incident, the use of sonar has been associated

with a large number of whale strandings around the world

But while beached whales continue to grab the headlines

Michel was keen to understand if other creatures

were experiencing the same fate

A group of giant squids were found stranded on the beach

The post-mortem analysis didn’t show any cause of the death

What he was about to discover would change scientists’ understanding

of the effects of ocean noise-pollution

This group of experts realised that a geophysics experiment

using high-energy sounds was performed a few days before this event

Oil-prospecting ships had unknowingly disturbed the ecosystem below them

We decided in our laboratory to recreate this situation

And we found this massive acoustic trauma

when we exposed this animal to sound

Although squid don’t have ears

their bodies contain small organs called statocysts

which are lined with noise-sensitive hairs

In his lab, Michel and his team discovered

that even low-intensity sounds destroy these hairs

and knock out the squids’ balance

We went through the idea that it was only affecting a few species

the whales and the dolphins, to invertebrates and fish

and we are speaking about thousands of species

So we cannot anymore consider the effect of noise as species-specific

but consider it as a global effect to the whole marine environment

This revelation has been the driving force behind Michel’s plan

to map the soundscape of the entire ocean

So this [click, click, click] they are shrimps

This is the sound of a ship passing by

So far he has built and installed 150 listening platforms around the world

What we do is we want to identify all the sounds, right

We don’t want to leave anyone out of this

so we want to know everything

To do that we need to train the system to recognise the features

that belong to one or another source

Every sound is being labelled and stored

in what is now the world’s biggest database of ocean sound

Using artificial intelligence, the sounds in the acoustic library

can be identified as natural or man-made

and the effects they’re having on marine life can be assessed

We aim at building trends that reflect the biodiversity of an area

If we detect an external event that could be a ship noise

or other human activity that will influence the area in a negative way

we will see how this trend changes because of this external factor

Researchers are trying to pin down the damage

that human activity is having on the ocean

and they’re revealing some concerning trends

Noise pollution is most prominent in the northern hemisphere

Every decade noise from shipping has doubled in intensity

which has been seen to have an effect on certain species of whale

reducing their ability to communicate with each other by about 60%

Air guns are the most common method

used to map the ocean floor for oil and gas exploration

Their impacts have been detected 4,000km from the source

and have been linked to multiple mass strandings

The South Pacific is the part of the ocean with the least human noise

The good news is that unlike other forms of pollution

the impact from noise is short-lived

If we compare sounds to other source of pollution

as soon as you switch off the sound, the effect is gone

But not all noise is bad and Michel and his team are trying to ascertain

how humans can best carry out important work

while limiting its effect on the ocean

Michel is now working with marine-based industries

to help them reduce ocean-noise pollution

In our laboratory we try to understand these effects

on the marine environment so we can provide the industry

that operates at sea with these tools that will allow them

to operate in the same way with a limited effect on the environment

Solutions include noise-reduction technologies

to lessen the sound of deep-sea drilling in the renewables sector

and potential alternatives to sonar

Michel André’s research is shifting science’s understanding of noise pollution

It’s just the beginning but his work could fundamentally change

the way in which humans operate on the ocean

and co-exist with marine creatures in the future

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