The oceans are often thought of as a silent expanse, but under the surface there is a symphony of sound: a secret soundscape of songs, whistles, chirps and clicks, which humans rarely get to hear. These essential sounds are what marine creatures rely on to gather and understand information about their environment.
Humans are increasingly polluting the oceans with noise. From ship traffic and recreational boats, to oil and gas extraction, wind turbine developments and military sonar; we expose marine life to a plethora of unnatural sounds which has a detrimental effect on their health. From the smallest species to the largest- it is now a global issue.
Unlike other forms of pollution, noise pollution is completely invisible, meaning it is often overlooked. Therefore, it is important to educate people on the impacts it has on marine species and the best ways to mitigate the stressors to prevent further damage to vulnerable ecosystems.
Why is Noise Pollution a Problem?
The sun disappears just a few hundred meters below the water surface, so sound is an effective means of communication which supports life in the oceans. Most species can’t see far underwater, but sound can travel for kilometres.
It is also much more than just a way to converse, animals use sound to find mates, locate prey, avoid predators and guide their navigation. A noisy ecosystem is a sign of a healthy ecosystem.
But, artificial sounds from humans end up disrupting the underwater world. Sadly, when a marine specie’s acoustics are impaired, so are their vital life functions. Research has found that it not only temporarily impacts their hearing, but in some cases, also has long term consequences for their development, reproduction, feeding, and physiology (Kight and Swaddle, 2011). More research has been done on marine mammals, but there are studies which also show how detrimental noise pollution is for smaller fish too.
The harsh reality of noise pollution in our oceans was first brough to the public’s attention back in 2002. Fourteen beaked whales washed ashore in the Canary Islands, bleeding from their ears. It was linked to high intensity sonar used during naval exercises (Fernandez et al., 2013). These shocking events led to the European Parliament stopping the deployment of high-intensity sonar until a proper assessment had been carried out on the cumulative effects it has on marine life. Sadly, events like this have been recorded many times since then and there are still no solid regulations in place to protect the marine animals that are most impacted.
Scientific research has highlighted how dangerous noise pollution is for marine species, so now it is time to take action. We need to dial down the volume of our oceans in order to protect marine life.
Commercial shipping is the most widespread and constant source of noise pollution in the ocean (Merchant, 2019). With global trade increasing, levels of underwater noise are only projected to increase further. It is necessary to take appropriate actions to control and mitigate the negative impacts. Ship quieting technologies are one such option which are gaining interest as the most effective way to address noise pollution from ships and smaller vessels.
The most significant source of noise from vessels is propeller cavitation (Merchant, 2019). This is the creation of small bubbles which are formed by the propeller rotating, which then make a loud noise when they collapse. Cavitation can be reduced substantially by modifying the blade shape and hull design. Good maintenance of the vessels can also be very beneficial. It is important to keep the hull in good condition because extra drag leads to an increased load on the propeller which makes it louder. Similarly, if the propeller is dented or covered in fouling it will increase cavitation and noise.
Machinery on board ships is another source of noise pollution which should be addressed. Engines and generators can be isolated and optimally positioned to produce less underwater noise. Electric engines are another possibility when it comes to reducing noise pollution (Jones, 2019). They run much more smoothly than diesel engines, resulting in a quieter vessel with fewer vibrations. Scientist found that these green technologies emitted only minor noise to the environment and saw a hundred-fold reduction in noise emissions. Alongside that, electric engines reduce CO2 emissions and air pollution to zero (Litwin et al., 2019).
Looking at these quieting technologies during the design stage rather than the retrofitting stage would help companies to reduce their costs (Spencer and Fischer, 2017).
Offshore Wind Farms
Offshore wind farms aren’t a problem during the majority of their lifespan, but the construction phase generates high amplitude pulses when the steel cylinders are driven into the seabed. The activity been shown to distress and displace resident marine species.
This temporary source of noise pollution could be addressed by finding alternative base solutions such as floating foundations. These would be much quieter to install, therefore disturbing the surrounding species less. Alternatively, acoustic barriers could be used during construction to dim the noise, or incentives could be introduced for the installation of fewer, larger turbines, to lessen the frequency of construction.
Another possibility to help with noise pollution is the introduction of “quiet sanctuaries” for sensitive and biologically important areas (William et al., 2015). It would be a relatively easy conservation method as it would require only small changes to current shipping routes. The focus would be on zones where marine mammals spend a lot of time; feeding areas, mating grounds and migration routes. This mitigation measure would also have the added benefit of reducing ship strikes.
What Does the Future Look Like?
There is no doubt that the current level of noise pollution in our oceans threatens marine life, but there are solutions available which can be implemented. The most noise polluting industries have options that they can transition towards in order to take the strain off already vulnerable marine ecosystems. With a combination of policy and incentive-based measures, effective noise reduction measure can be imposed while avoiding unnecessary disruption to industries.
The positive thing about noise pollution is that once it is stopped, it has gone. You are not left with any remaining pollutants that continue to harm marine life.
Fernandez,A., Arbelo, M, Martin, V. 2013. No Mass Strandings Since Sonar Ban. Nature 497.
Jones, N. 2019. Ocean uproar: saving marine life from a barrage of noise. Nature 568, 158-161.
Kight, C., and Swaddle, J. 2011. How and why environmental noise impacts animals: an integrative, mechanistic review. Ecol. Lett. 14, 1052–1061.
Litwin, W., Lesniewski, W., Piatek, D., Niklas, K. 2019. Experimental Research on the Energy Efficiency of a Parallel Hybrid Drive for an Inland Ship. Energies 12, 1675.
Merchant, N. D. 2019. Underwater noise abatement: Economic factors and policy options. Environmental Science & Policy, 92, 116-123.
Williams, R., Erbe, C., Ashe, E., Clarke, C. 2015. Quiet(er) marine protected areas. Marine Pollution Bulletin 100, 154-161.