The not-so silent world: noise in the underwater environment

Sarah Ward

Living Seas Officer

It’s quite poetic to think of the underwater world as being a peaceful, quiet place, just like as suggested by the title of Jacques Cousteau’s book and later documentary-film, The Silent World. Although when you venture underwater, it can feel like a relief from the relentless noises we are used to above the surface, there is actually an abundance of both natural and anthropogenic sources of noise under the sea. In fact, sound travels around 4.5 times faster and 60 times further through water than air!

Many marine creatures create all sorts of weird and wonderful sounds; if you ever snorkel or dive on a coral reef, you’d be unlikely to miss the sound of parrotfish, which use their beak-like mouths to scrape algae off rocks. Or perhaps even a snapping shrimp, which makes a ‘pop’ sound with its claw, one of the loudest sounds in the ocean! Closer to home, marine mammals use a variety of clicks and whistles to communicate, navigate and understand the world around them.

Anthropogenic sources of noise are becoming an increasing issue in the underwater environment. As we make more and more use of the sea for development, this inevitably comes with associated noise. Sources of noise may include shipping and other vessels, pile driving and construction, wind farms, and even military activity. As a scuba diver, I’ve always found it quite alarming when the loud rumbling of a boat engine passes overhead – it must be incredibly disturbing for marine life. In fact, it is widely understood that anthropogenic noise can affect many kinds of behaviour in marine creatures, including the ability to navigate, find food or mates, and evade predators. In extreme cases, animals have even completely abandoned habitats to escape noise.

With this in mind, it’s really important to consider the potential effects of underwater noise when development is happening at sea. For example, construction may need to mitigate the noise created by using particular techniques or avoidance measures in order to minimise disturbance to marine life.