By: Anushya Nedunuri
Photo by Quang Nguyen Vinh on Pexels
Boom! Boom! Boom! Sounds of destruction and fear only heard through the walls of the sea. Organisms underwater can’t figure out the problem and are stuck in a trap, waiting to be free again.
Underwater noise pollution refers to sounds created by human activity that interferes with marine life. There are several ways in which humans have altered the ocean sounds including shipping, on-land transport, oil drilling, naval exercises, and seismic surveys.
90% of human goods are transported by ship, which may sound great, but in reality, shipping causes severe consequences for marine life. Large vessel engines make a lot of low-frequency noise. The presence of low-frequency noise in the ocean has increased 32-fold in the last 50 years solely from shipping. The loudest ships omit sound blast at approximately 190 underwater decibels, to put that into perspective, that's the on-land equivalent of a jet taking off. Imagine living in an environment where it's impossible to escape those jarring noises day and night. Land traffic on bridges can also add to the problem by contributing to low-frequency noise through underwater penetration. Oil drilling is a significant contributor to underwater noise pollution. Underwater drilling into the seafloor with air guns and seismic blasts to get to oil, sends ripples of noise out into the water. Additional contributors to noise pollution include warfare activities, coastal construction projects, seismic surveys, and sonar-based navigation. This list is continually expanding as new sources of noise pollution emerge.
Climate change can also worsen noise pollution. The melting of ice allows for newly accessible areas that humans can overtake with activities like shipping and mining. Even activities that promote climate change prevention, such as building wind farms, produce noise that may harm aquatic organisms.
There is a reason why sound hurts and affects marine species differently than humans and terrestrial animals, much of which has to do with density. Water is denser so sound waves travel farther and faster in the ocean, low-frequencies in particular can travel vast distances. Aquatic organisms also hear a wider range of frequencies than terrestrial organisms. Sound wakes up the water molecules, which then expand and waves are spread in all directions. When sound waves travel vertically in the water, they go through the seafloor and then bounce back upward. In the presence of anthropogenic noise, the sensory link for marine species is gone, and mammals struggle to hear echolocation pulses necessary for daily activities and survival.
Many marine mammals use echolocation, a process that relies on reflected sounds to pinpoint objects, find food and mates to reproduce, communicate, and navigate the ocean. Noise pollution has made it difficult for marine mammals to distinguish the sounds of the environment and each other. Sometimes sounds from ships and machines can mimic that of a marine organism, causing further confusion and difficulty in behavioral adaptations. Just like humans, marine animals like to escape noisy areas and move to quieter areas. Unfortunately, as noise from human activity travels far and wide and is practically always present, it is difficult for organisms to escape. Their natural marine habitat starts to shrink forcing them to adapt to new environments with limited resources.
Unlike other environmental problems like climate change and ocean acidification, noise pollution can be easily fixed. Noise pollution is a direct result of our activities in and near the ocean, and can be ended in an instant if those activities are stopped. It is really important to reduce noise pollution as much as we can to reduce the stress from other environmental problems on these creatures. We can start by advocating for the manufacturing of quieter ships. Cavitation bubbles are the main source of propeller noise, through careful design and frequent repairing and polishing of propellers, noise can be reduced. Reducing ship speed by 10% to 20% has also been shown to diminish noise by up to half. Reducing sonar sound effects can be done by shifting navy exercises away from the known feeding grounds, tracking whales, and slowly increasing sonar sounds so that organisms can escape. Technologies can be applied to seismic surveys to quiet them down as well.
Of course reducing ship traffic, navy exercises, drilling, and surveys would yield the best result in lowering noise pollution underwater. While it isn't probable that these activities will be slowing down, there are things we can do to reduce their sounds. On an individual level, you can help by educating the community and advocating for change. A little peace and quiet and sympathy for marine mammals can be more beneficial than you think.
Baker, A. (2021, February 5). Underwater Noise Pollution Is Disrupting Ocean Life—But We Can Fix It. TIME. https://time.com/5936110/underwater-noise-pollution-report/
Bernstein, S. (2021, February 4). Noise pollution is harming sea life, needs to be prioritized, scientists say. Reuters. https://www.reuters.com/business/environment/noise-pollution-is-harming-sea-life-needs-be-prioritized-scientists-say-2021-02-04/
Haskell, D. G. (2022, April 12). An ocean of noise: How sonic pollution is hurting marine life. The Guardian. https://www.theguardian.com/environment/2022/apr/12/ocean-of-noise-sonic-pollution-hurting-marine-life
UNEP. (2022, April 25). Are humans drowning out the sounds of the seas?. UNEP. https://www.unep.org/news-and-stories/story/are-humans-drowning-out-sounds-seas
WWF Global Arctic Programme. (2023, January 4). Infographic: Underwater Noise. WWF. https://www.arcticwwf.org/the-circle/stories/infographic-underwater-noise/