Noise pollution is regular exposure to elevated sound levels that may lead to adverse effects in humans or other living organisms.
We have noise pollution on land and it has been shown to cause hearing loss, stress, sleep disturbances, and other issues in humans. Similarly, terrestrial noise pollution affects wildlife by reducing habitat quality, increasing stress and masking other sounds that may be necessary for hunting, communication, predator avoidance, and other essentials.
Sound travels 4x faster in water than on land and can travel for kilometers. Therefore, disturbing or unwanted noise in the ocean can travel very far and affect many different animals.
Naturally, the ocean is not at all silent; sounds come from breaking waves, rain, storms, underwater volcanoes, hydrothermal vents, cracking ice, earthquakes, and, of course, marine life. The ocean is naturally so noisy that sonar operators in the Second World War confused the sounds made by whales with noises from German U-boats.
As humans are using the ocean more and as technology advances, human contributions to marine sounds are drastically increasing. Human-created ocean noise sources include ships, seismic surveys, oil exploration, sonar, air guns, dynamite fishing, speedboats, and the list goes on. The most pervasive contributor to ocean noise is shipping noise, 85% of which comes from propellers. All of this makes the ocean an incredibly noisy place for marine life.
In the ocean, visual cues can disappear after a few dozen meters, and chemical cues can dissipate after a few hundred meters. Sound can travel thousands of kilometers and connect animals across huge regions, even in darkness. Many marine species are adapted to detect and communicate with sound.
Sound is for whales and dolphins (cetaceans) what sight is for humans. Marine mammals communicate underwater using: short pulses and whistles, clicks for navigation and social interaction, different vocal dialects, low frequencies for long distances, they even have special structures in their jawbone to assist in hearing all of these sound vibrations.
But it’s not just marine mammals that use sounds underwater, nearly every ocean animal relies on sound in some way. Ocean noise impacts seals, fish, squid, crustaceans, sea turtles, and invertebrates. They all have adapted to use sound to hunt, find mates, reproduce, navigate and migrate, communicate and avoid predators. Therefore, all of this non-natural underwater noise can threaten marine life.
The most striking example is the stranding of whales and dolphins. Noise pollution can cause stress and panic; extreme noise pollution (such as sonar maneuvers) can cause vascular damage to the brain, lungs and other organs, which leads to embolism and even death.
As with humans, extremely loud or prolonged loud noises can permanently damage hearing, with dire consequences since many marine creatures depend on hearing for communicating, sensing danger, finding a partner and hunting prey. In some areas, the sediment stirred up and the noise generated by sand boats can interfere with porpoises’ vision and sonar so drastically that they cannot find fish and shrimp to feed on.
Fish can lose their ability to school, stress can cause impaired growth in shrimp, even lobsters have been found to have cellular changes. Similarly cellular damage has been found in invertebrates like jellyfish and anemones, which are vital food sources for tuna, sharks, sea turtles and other creatures. And, as in all living creatures, stress weakens the immune system making animals more susceptible to other illnesses. If noise pollution in an area persists, it can cause marine animals to flee their natural habitat, either to escape the noise, or to follow their food source which is escaping the noise.
All of this points to additional stressors on already stressed marine animal populations.
As an example, baby clownfish (Nemo!), after hatching, are adrift in open seas in their larval stage. When they are big enough to swim against the tide, they listen for the sounds of the reef: snapping, grunting, gurgling, popping and croaking. These noises tell them which direction to swim to make their home. If noise pollution is creating too many conflicting sounds these fish cannot hear the reef and may be adrift forever.
Underwater noise pollution is an immense problem for marine animals. Noise exposure can cause hearing damage, impair the sense of direction and, in the worst case, lead to stranding or death. How are humans causing so much noise in the ocean to do this much damage to marine life?
Shipping is the most common source of manmade noise in the ocean. Ships and other motorized vessels produce a range of sound frequencies which overlap with the frequencies produced by whales and other marine mammals. Vessel noise is particularly chronic and loud in coastal areas near active shipping lanes, ferry routes and ports.
Although shipping noise has a variety of sources (diesel engines radiate vibrations through a ship’s hull), about 85 percent comes from propellers. The low pressure generated by the propeller causes thousands of tiny bubbles to form which create noise when they collapse. This is called “cavitation” and the good news is that cavitation can be fixed, with an incentive to do so.
Active sonar is used by military vessels during exercises and routine activities to search for objects such as enemy submarines. These mid- and low-frequency sonar systems emit sound pulses of more than 100 seconds at a time for hours on end thus interfering with hearing for up to a 3,000km radius.
Seismic airguns are primarily used for oil and gas exploration below the seabed and for geophysical surveys of the seafloor. Air is driven into the water at high pressure, sending intense and explosive sound pulses towards the seabed. These sounds can permeate thousands of metres of ocean before penetrating hundreds of kilometres into the ocean floor. Up to 40 airguns are fired in a tight sequence, each of them emitting sound every ten to fifteen seconds, often for 24 hours a day and for several weeks in the same area.
Watch this video for more information on seismic surveys
Construction works in harbors and pile driving generate intense noise pollution. Pile driving is the practice of pounding long hollow steel pipes (called piles) into the ocean floor, to support underwater structures. It is frequently used to build turbines for the purpose of tapping into natural energy sources such as oil, gas, and wind.
Not surprisingly, when explosives are detonated in the ocean they cause an incredible amount of noise over a large area and across wide frequencies. They are used by the military, for demolition purposes, for fishing, or for testing equipment.
Deep Sea Mining
Researchers have suggested that deep sea mining, an industry in its infancy, could become a major source of underwater noise pollution. This gives corporations and governments a chance to proactively design technology to minimize noise pollution before commercial deep sea mining is authorized.
Unfortunately, the many threats facing our ocean can have a cumulative effect. Worldwide overfishing and loss of important ecosystems such as mangroves, seagrass, and coral reefs, have decreased the natural sounds generated by marine life. Global warming has also been shown to alter ocean sounds from geophysical sources such as sea ice and increasingly forceful storms.
Although ocean noise pollution is a serious problem, the good news is that noise pollution, unlike plastic pollution or temperature changes, can be stopped immediately. Even better, we have the technology to reduce much of the marine noise pollution we create. One of the biggest obstacles to making these changes is the public’s lack of awareness of the problem.
Of course, some of the changes needed are much bigger than one individual, but one individual can spread the message and raise awareness of this important ocean threat! Tell others about the impact of ocean noise pollution, encourage ocean users (individuals, corporations, governments) to make necessary changes and support those who do! With public awareness and public pressure, corporations and governments will make changes.
You have the power to create impactful change through your consumer habits. Think about where your purchases come from and try to buy locally. Buy fruits or vegetables in seasons and from your own country; not those shipped from the other side of the world. Shop for products at local stores. Do your part to reduce ships on our ocean.
Support Organizations Working Toward Solutions
There are some great organizations working with national governments and international groups to address the impact of ocean noise pollution. Get on their mailing lists to remain informed. Donate time, money, or your services to help in their cause. And spread the word.
Be a Responsible Boat Owner
Slow down; reducing speeds already reduces ocean noise. Be sure to operate below the cavitation speed and avoid rapid acceleration. Maintain clean hulls and propellers to reduce cavitation noise pollution.
Support Local, National, and International Regulations
There are no international regulations on ocean noise. Ocean noise should be explicitly recognized as a serious form of international ocean pollution to be addressed. On the national level, some countries are doing more than others.
On all levels, stronger legislation and regulation is needed to minimize ocean noise pollution. Get involved in the process or lend your support to those who are involved.
Port of Vancouver, Canada
Canada was the first country in the world to provide incentives for quieter ships. The Port of Vancouver introduced incentives to reduce ocean noise pollution. Ships that have reduced their noise pollution get reductions in port fees of up to 47 per cent.
The worldwide pandemic offered a rare glimpse of what can happen (and how quickly) if we reduce noise pollution. Shipping activity slowed down, the oceans fell relatively silent, and marine mammals and sharks returned to previously noisy waterways where they were rarely seen; and this recovery happened almost immediately. Research is on the way to determine the exact reduction of marine noise during this period. It is suggested that the noise levels during 2020 was close to what the oceans would have sounded like 150 years ago. And while it’s strange to call a worldwide pandemic a “success story,” the success is the certainty that noise reductions can have almost immediate positive effects.
Maersk, Propeller Cavitation
Proving that propeller cavitation can be fixed and subsequently can have a substantial impact, Danish shipping company Maersk spent more than $100 million in 2017 to save fuel by retrofitting hulls and installing more efficient propellers. After acoustical testing on five of these ships, they were found to have a 75 percent reduction in acoustic energy!
Whale Report Alert System
The Whale Report Alert System was launched in 2018. It is a mobile and desktop-based program to alert commercial mariners to the presence of whales. This allows ships to slow down or divert their course when in the presence of whales in hopes of mitigating ocean noise damage and possible ship strikes.