Underwater symphony: how human noise is disturbing the ocean’s soundtrack

3 March 2021

While 2021 is the International Year of Sound, a global community of scientists are asking us to tune into the drowning sounds of the ocean.

There is an acoustic symphony playing under the sea – a hidden soundtrack composed by marine life – echoing even in the darkest depths of the ocean, travelling faster and louder than ever possible in the air.

This unique ‘soundscape’ is orchestrated by complex marine ecosystems and marine life have successfully depended on it for their survival for thousands of years – that is, until humans came along.  

A recent global study has found human activities are interfering with this soundscape, with anthropogenic noises disrupting the ocean’s natural rhythm, stressing marine life and causing a decline in the health of ocean ecosystems.

The study, published in Science, is the largest collaboration of evidence on the effects of the human-driven noise in the ocean, and is co-authored by Dr Mark Meekan and Dr Miles Parsons who lead Australian Institute of Marine Science’s research on marine noise, both human-made and natural.

 

The natural soundscape: why all the noise?

For marine animals, sound is a composition of communication – a crashing wave is heard by an oyster, signalling incoming food; a whale’s mating song can travel thousands of kilometres; a dolphin navigates murky waters by clicking, creating sound waves that bounce back off objects; a squid uses sound pressure to detect and catch prey; and even fish, swimming out at sea, are listening carefully to the wind, the waves, the rain, and the currents to understand their environment.

Coral reefs have signature melodies, too – with fishes and invertebrates creating pops, grunts and croaks while they forage, hunt, feed, groom and mate. Every reef has a signature sound, of low and high frequencies, signalling the health of the reef and the type of predators that may inhabit it. Even fish larvae, once thought to be drifting aimlessly, can hear and identify such reef signatures, and choose whether it’s a good place to call home.

AIMS’ scientist Dr Mark Meekan said a healthy ocean is not quiet, with sound being key to communication underwater and critical for the survival of marine life.

“Marine life exists in an environment where many sensory cues are restricted in their use, making sound profoundly important,” he said.

“Noise is used and created to find prey, attract mates, escape predators and navigate their habitat.

“Whether it be a crab, a clam, a dolphin or a fish – almost all fauna use sound one way or another for vital life functions.”

Composition from the Soundscape of the Anthropocene Ocean (© Jana Winderen)

How does human driven noises interfere with the ocean’s soundscape?

The international team of researchers found human-driven noise – including vessel noise, coastal development, exploration, naval operations, dredging, pile driving, and deep-sea mining – is changing the natural soundtrack, and further disrupting the behaviour, reproduction and physiology of marine life.

Dr Miles Parsons said this intrusion has been linked to hearing disabilities in marine life, displacement from preferred habitats, decreased health and reduced communication.

“When human-driven noise drowns out the natural sounds, it can potentially result in marine life missing vital sound cues for capturing prey or failing to avoid a predator,” he said.

“On-going, chronic noise, like the constant sound of passing vessels, can disrupt traveling, foraging, socialising, communicating, resting, and other behaviours in marine mammals. 

“We often think of the ocean as an untouched soundscape – deep and dark – but sounds from the surface and in the water travels much faster and louder compared to the air.

“Even the pattering sounds of rain echoes beneath the water’s surface, so it’s easy to imagine how noises made by humans can interfere with the natural seascape.”

How can we turn down the volume?

Human activities are impacting the ocean’s soundscape – but there are also tangible solutions, with some of these solutions already in motion. 

Dr Miles Parsons said human noise in the ocean can be responsibly managed through improved and collaborative efforts.

Whaleshark

“This could include improving regulations to manage sound within exclusive economic zones,”    he said.

 “The speed and routes of ships can help reduce noise or divert the effects of marine noise away from biologically sensitive areas.

“We’re already seeing marine construction, particularly for offshore wind farms, using noise-dampening technology which is making rapid changes to reducing noise.”

Australia is a marine nation, with the marine industry doubling in the past 10 years and injecting billions into the Australian economy. 

“AIMS’ scientific research provides knowledge that contributes to the sustainable productivity of many of our marine industries that we rely on,” Dr Miles Parsons said.

 “Our research helps ensure this occurs in a way that preserves and protects our unique marine ecosystems now and in the future.”

“We are seeing marine industries improving their practices, so it is about continued efforts to ensure marine life can still rely on the natural ocean soundtrack.”

The research paper The soundscape of the Anthropocene ocean was published in the journal Science on 5 February 2021.

AIMS research on sound