Oceans of noise

Feb 22, 2021

by Claudia Afeltra

cetaceans, climate change, conservation, conserve dolphins, dolphins, hearing, ocean, ocean noise, porpoises, protection, seas, sonar, sound, Whales

Noise pollution in the ocean is a major problem, and it’s getting louder. A study has recently been undertaken on the subject of human-caused noise in the marine environment – the first comprehensive assessment of this important issue. The study points out that acoustic pollution is as significant a threat to marine life as overfishing, climate change and other forms of pollution, but that it is being overlooked. In a review of studies assessing the effects of noise pollution in the ocean, 90% concluded that it caused significant harm to marine mammals and 80% found that there were also detrimental impacts on fish and invertebrates.

Hearing is crucial to cetaceans. It’s their most sensitive sense and is fundamental to every aspect of their lives. In fact, most marine species utilise sound as their principle sense. In the murky depths of the sea, vision can only get you so far, but sound can cover much larger areas. Whales and dolphins depend upon their excellent sense of hearing to communicate with each other, feed and navigate. Sound waves underwater are more powerful than in air, and they travel a considerable distance. This means that the unnatural noises invading the oceans can disrupt marine life over vast areas. The fact that ocean warming increases the acidity of the water makes it worse, as more acid water allows sound waves to travel even further.

*Dolphins depend on their hearing to survive. Photo credits: G Pesante*

Excessive noise severely affects the ability of whales and dolphins to effectively communicate with their pods, find their way and forage or hunt, which are necessary for them to lead normal, healthy, natural lives. It also causes stress, confusion and disorientation, and has been linked to mass strandings of whales, such as the beaked whales in Scotland last year. Excess noise can also mean increased movement of cetaceans as they attempt to avoid it, and can displace them from their natural feeding and breeding grounds. Very loud noises such as underwater blasts can irreparably damage their hearing and lead to death.

Causes of acoustic marine pollution are copious and include shipping, motor boats, oil rigs, wind farms, detonation of old WW2 bombs, ocean floor drilling, construction and the use of sonar by military and fishing boats. Military sonar is perhaps the most damaging. All of these things have increased in capacity over recent years, and oceans have been getting progressively noisier since the industrial revolution. Around the UK, ocean traffic is relentless. In the North Sea there are more than 400,000 ship movements per year. Seismic exploration for oil and gas is now taking place in waters west of Scotland which are very rich in cetacean life.

*Increased shipping is a threat to cetaceans. Photo credits: PGH Evans*

There are solutions out there to reduce marine noise that would be easy to implement. In terms of boats, new propeller designs, switching to electric motors and reductions in speed can all help hugely. Other activities need to be strictly monitored with strong regulations in place to reduce disturbance and protect marine life. Military sonar, being the most potent auditory threat, needs to be significantly limited.

“We need tenacious policies to monitor the activities causing marine noise, propose suitable solutions and enforce new rules”.

The strict lockdown that began in March 2020 due to the coronavirus outbreak must have been bliss for marine life, as the reduction in human activity across the globe would have all but silenced the ocean in terms of anthropogenic noise. The beneficial effects of a quieter ocean would be fairly immediate, as the negative impacts quickly decline when the source of the noise is removed.

We cannot keep seeing the ocean as something to be exploited. For our sake and that of the wonderful creatures that live there and depend upon it for their survival, it needs to be better protected. In addition to the many other threats to the ocean, such as plastic pollution, overfishing, warming and acidification, the detrimental effects that noise pollution has on marine life need to be acknowledged and accepted, and actions taken to mitigate them.

All life began in the ocean, and we owe it everything.

Kayleigh
Sea Watch Volunteer
Feature Blogger

Sources and further information