Oceans are too noisy for marine life, study finds

Jon Deery weighs in on new research unveiling the darker side of acoustic disturbance in the ocean

Jon Deery
18th February 2021
Featured Image credit: Chris Pagan on Unsplash
In the ocean, sound plays a crucial role in “feeding, navigation, communication and social interaction” for all life, scientists say. But due to human activity, marine organisms now live in an unpredictable and cacophonous soundscape, where sound waves are as dangerous as fishing boats and the warming temperature.

In an article published in the journal Science, researchers noted that, “over the past 50 years, increased shipping has contributed an estimated 32-fold increase in the low-frequency noise present along major shipping routes.”

They also cite a number of other sources of noise pollution, including controlled bomb detonations, sonar, low-flying planes, construction of oil and gas infrastructure, and technology that scrapes the bottom of the ocean, like the kind used by fishing trawlers.

Image credit: Nicholas Doherty on Unsplash

Sound travels faster in a warmer ocean

This issue is further exacerbated by the emission of greenhouse gases that are warming our planet’s atmosphere. According to the study, “climate change directly affects the temperature, heat content, and stratification of the ocean, with sound traveling faster in a warmer ocean.”

This occurs “to the extent that long-range acoustic transmissions have been used to measure large-scale ocean temperature and heat content—a phenomenon that W. Munk termed “the sound of climate change.””

Marine life forms use sound for a multitude of essential functions, including navigation, foraging, displays to ward off predators, defense of their habitats, and the attraction of mates. All of these functions are potentially being compromised by the additional human background noise.

Image credit: Pascal Müller

“Anthropogenic noise can interfere with natural auditory signal processing by marine animals, an effect termed “masking”, which reduces their communication space,” the authors write.

Their analysis intends to draw political attention to changing ocean soundscapes, which the authors say have become “the neglected “elephant in the room” of global ocean change.”

The benefits of cutting off anthropogenic noise pollution will be apparent almost immediately

“A “business-as-usual” development of the ocean-based economy,” they write, “will inevitably lead to ever-increasing noise from more shipping, coastal development, seismic surveys, military operations, dredging, pile driving, and deep-sea mining, likely contributing to increasing impacts on marine biota.”

It is therefore necessary to implement new legislation on ocean noise as quickly as possible. Fortunately, noise has a distinct quality that other pollutants don’t - the benefits of cutting it off will be apparent almost immediately. Life will return to more natural behavioural patterns in a short space of time.

Image credit: NOAA on Unsplash

Solutions to this problem are extremely cost-effective, too. As an example given in the paper, “in 2015, Maersk underwent a retrofit of five large container ships and found that reducing propeller cavitation decreased low-frequency sound pressure levels by 6 to 8 [decibels] while improving fuel efficiency.”

In short, more energy-efficient propellers also mean quieter oceans; a win on all fronts. The authors also promote “regulating the speed and routes of ships,” perhaps diverting faster vessels away from “biologically sensitive areas” to minimise overall damage.

The authors note that their report’s release “is particularly timely, given that 2020—and now, because of COVID-19, 2021—is the International Year of Sound.”

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