What Is Underwater Noise Pollution?

When we think of noise pollution, we normally think of the clatter of construction sites, the rattle of a midnight train or perhaps even a boisterous party in the upstairs flat that shows no signs of slowing down even into the wee hours of the morning. We rarely think of the world beneath the waves.

However, the ever-increasing and apparently irrepressible creep of human activity is more and more of a fixture in today’s seas and oceans, as well. The thrum of motorboats and shipping vessels, the bleep of sonar signals and the almighty explosions from underwater detonations threaten to disrupt and endanger the lives of countless marine animals, according to experts on the topic.

Marine life at risk

Human activity poses a number of different threats to life in our seas and oceans. Most obviously, the over-fishing of our waters, rising temperatures due to manmade climate change and increasing concentrations of pollution (often exacerbated by the challenges of flood control) put marine life in jeopardy.

However, there is a growing body of evidence which suggests that underwater noise pollution might have a more subtle but still significant effect on water-dwelling animals. Drowning out the sounds (and even sights and smells) of predators, prey and potential mates, manmade noises can endanger the feeding and breeding habits of fish and mammals – as well as making them more susceptible to predators.

Communication breakdown

Mammals such as whales rely on sonar to communicate, while many species of fish use acoustic clicks, chirps and grunts to get their point across. If a loud source of manmade noise pollution is in the near vicinity of these animals, it may be impossible for them to “hear” one another, thus resulting in difficulties finding food, a mate or escape from a predator. Indeed, a recent study even found that noise pollution can cause heightened stress levels in whales.

It’s not just their sense of hearing which can be compromised by noise pollution, either. Cuttlefish, for example, change the colour of their scales to communicate important messages with each other. A collaborative study published in the journal The American Naturalist found that exposure to noise pollution had a marked effect on these visual signals, potentially impairing communication.

Can’t hear themselves think

Fish have also been found to struggle to learn or process information when in the vicinity of a loud source of noise pollution. One study from the Lizard Island Research Station on the Great Barrier Reef trained some damselfish to recognise the scent of a dottyback (a natural predator) in the presence of the noise from a motorboat, while others received their education with normal levels of oceanic noise.

It was found that those trained in the presence of the boat did not register the presence of the dottyback as a threat, while those in the open waters showed clear signs of distress. More conclusively, a mere 20% of those trained with the boat noise as a backdrop had survived three days of the study, opposed to over 70% of those who were not exposed to the pollution.

Time for a change

Clearly, underwater noise pollution can have a seriously debilitating effect on life under the waves, and it is our responsibility to reduce our impact as much as reasonably possible. This could possibly be achieved through the installation of muffling equipment or the use of low-volume engines, as well as the implementation of speed limits and quiet zones. The future of the marine world may depend upon it.