Brian Barton
Sources of noise pollution in the ocean include human activities such as commercial shipping, sonars, seismic surveys, exploration, construction, and military activities. Marine dredging, oil and gas drilling, and seismic air guns used in the search for gas and oil deposits also contribute to the increasing noise levels in the ocean. These activities have been shown to negatively impact marine life, causing hearing loss, behavioural changes, injury, and even death. The noise interferes with the natural behaviour and communication of marine mammals, affecting their migration, navigation, feeding, and ability to detect predators. As global shipping and underwater noise pollution continue to increase, it is crucial to implement measures to reduce noise emissions, such as using quieter technologies and sound-absorbing ship designs, to protect marine ecosystems and the health of marine species.
| Characteristics | Values |
|---|---|
| Sources of noise pollution | Sonars, seismic surveys, commercial shipping, construction, seismic air guns, military activities, oil and gas exploration, marine dredging, propeller noise, pile driving |
| Impact on marine life | Hearing loss, behavioural and physiological changes, masking, injury, death, deviation from migration routes, reduced communication, stress, disrupted feeding, hindered mother-calf communication, fright |
| Marine species affected | Whales, dolphins, fish, invertebrates, mollusks, prawns, sea turtles, lobsters, crabs, shrimp, humpback whales, beaked whales, minke whales, killer whales, sea bass, snapper, goldfish, cod, haddock, bluefin tuna, squid, lobster |
| Solutions | Quieter technologies, sound-absorbing ship technologies, slower ship speeds, quieter shipping guidelines, ending seismic surveys, transition to renewable energy sources |
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What You'll Learn
Seismic surveys
The impact of seismic surveys on cetaceans, including whales and dolphins, has been well-studied. Research has shown a decrease in sightings of baleen whales and toothed whales during active seismic survey periods. Baleen whales are particularly vulnerable due to the overlap of airgun noise with their hearing sensitivities and communication frequencies. Seismic surveys have also been found to negatively affect humpback whale singing activity off northern Angola.
The noise 'footprint' of seismic surveys is large, especially in deep waters, and can cause temporary threshold shifts and behavioural responses in marine mammals. The noise from these surveys can propagate into the deep ocean and contribute to low-frequency noise, which can be detected by cetaceans over large distances. This can lead to behavioural changes in these animals, such as avoidance and increased anti-predatory behaviour.
In addition to the impact on cetaceans, seismic survey noise has also been shown to negatively affect zooplankton. Furthermore, the continuous nature of seismic blasts can mask the communications of marine species, making it difficult for them to hear and avoid danger. This may put whales at greater risk of ship strikes or separation from their calves or pod.
The use of seismic air guns for oil and gas exploration has come under scrutiny due to its direct impact on marine life. The sound produced by these air guns can interfere with the communications of underwater species and reduce fish catches. It is important to reduce noise pollution in the ocean to protect both marine life and human populations in coastal areas.
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Ships and shipping noise
The constant underwater noise generated by vessels has been described as an "acoustic fog" that disrupts the natural soundscape of the marine environment. This noise pollution is caused by the global shipping industry, which runs day and night, and has increased massively in recent decades—up to 90% of internationally traded goods are now transported by sea. As a result, ocean noise pollution in many marine areas has doubled every decade since the 1960s, with noise levels in European waters doubling between 2014 and 2019.
The noise created by ships comes from their propellers and engines, with cargo vessels producing very low-frequency sounds that can travel hundreds of kilometres underwater. This constant drone masks the natural sounds of the sea, such as the clicks, whistles, and songs used by marine mammals to communicate with their young, search for food, find mates, and avoid danger. For example, fin whales stop singing when noise levels from ships drown them out.
The impact of ship noise on marine mammals can be profound, causing behavioural and physiological changes. Studies have shown that the population of cetaceans (whales and dolphins) has declined in areas prone to noise pollution from ships. In addition, increased ship noise has caused bottlenose dolphins to simplify their vocal calls, potentially reducing the effectiveness of their communication. Other species, such as narwhals, modify their vocalizations and head toward shore when exposed to ship noise.
The good news is that there are ways to reduce ship noise and mitigate its impact on marine life. During the COVID-19 pandemic, there was a decrease in shipping traffic, and marine mammals returned to their original habitats, and some fish populations thrived due to decreased noise pollution. This period demonstrated the effectiveness of measures such as reducing ship speeds, which has been calculated to reduce noise emissions by up to 67%. Other solutions include the development and implementation of ship-quieting technologies, which can also increase fuel efficiency and decrease environmental impact.
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Military sonar
The use of military sonar has been linked to adverse effects on marine life. Even at lower sound levels, blue whales have been observed to alter their behaviour in response to active sonar, stopping feeding, increasing their swimming speed, and moving away from the sound source. This can have significant impacts on their fitness, foraging ecology, and population health. In some cases, whales have been known to swim hundreds of miles, change depth rapidly (sometimes leading to bleeding from the eyes and ears), and even beach themselves to escape sonar sounds.
The impact of military sonar on marine life was highlighted in a 2003 lawsuit against the Navy by the NRDC, which resulted in restrictions on the use of low-frequency sonar off the coast of California. Environmental groups continue to advocate for curtailed testing, especially during peacetime, to give marine wildlife a chance to flee affected areas.
The intense sound waves generated by military sonar can cause direct physical harm to marine mammals, with sounds exceeding 230 decibels, comparable to a rocket launch. Such noise levels can lead to internal injuries and, in extreme cases, even death. Studies have estimated that certain sonar testing could kill tens of thousands of marine mammals and cause permanent injuries to hundreds more.
To reduce the impact of military sonar on the marine environment, policies and regulations must be implemented to mitigate the sound levels of sonar equipment. Quieter technologies and gradual testing procedures can help reduce noise pollution and enable the recovery of marine life. The International Maritime Organization (IMO) has established guidelines encouraging quieter ship designs, including modifications to hulls and propellers, to minimize underwater noise pollution.
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Marine dredging
The noise emitted during marine dredging can have several impacts on marine life. While direct collisions with dredging vessels are considered unlikely due to their slow speed, the noise they produce can lead to masking and behavioural changes in marine mammals. Masking occurs when the noise from dredging overlaps or covers the biologically important sounds used by marine organisms for communication and navigation. This interference can result in reduced or distorted communication, transmission of misleading information, and even disorientation in marine species that rely on sound for migration and habitat location.
Additionally, the noise from marine dredging can cause indirect effects on marine ecosystems. It can affect the survival and recovery of seagrass beds, which play a crucial role in primary productivity, nutrient cycling, and sediment stabilization. The changes in sediment type and nutrient load caused by dredging can impact the food web dynamics and the ability of juvenile marine organisms to find shelter.
The impact of marine dredging noise on marine mammals and other species varies. Some species may be more affected than others due to differences in sound frequency sensitivity. While cetaceans like whales and dolphins might show a degree of resistance, soft-shelled species such as mollusks, prawns, and certain types of fish are more susceptible to the negative effects of noise pollution.
To mitigate the noise pollution caused by marine dredging, implementing sound-absorbing technologies and avoiding sensitive breeding grounds of marine species are essential. Developing quieter dredging techniques and reducing the use of noisy equipment can also help minimize the impact on the marine environment and the organisms that rely on sound for essential life functions.
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Seismic air guns
Studies have shown that the use of seismic air guns can interfere with or overlap with the underwater species' communications. It can also affect the regularity of sightings of these animals near the shores and reduce fish catches. In addition, the noise from seismic air guns can cause hearing loss in fish, as seen in a study where fishes were placed in cages and exposed to airgun shots. The species with the most sensitive hearing showed the most effect from the airgun exposure, with hearing loss observed.
The use of seismic air guns has also been shown to disrupt the behaviour of marine mammals. For example, humpback whales deviated from their predicted heading and decreased their swim speeds when exposed to air gun noise. Atlantic spotted dolphins showed a significant, short-term avoidance response to airguns within approximately 1 km of the source. These changes in behaviour can have significant impacts on the health and survival of these species.
To reduce the impact of seismic air guns on marine life, policies and regulations need to be implemented to mitigate the sounds produced by these devices. Quieter technologies should also be developed to make it easier to reduce noise pollution in the marine environment. By taking these actions, we can improve the ocean soundscape and potentially enable the recovery of some marine life.
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Frequently asked questions
Some of the sources of noise pollution in the seas are human activities such as commercial shipping, sonars, exploration, construction, and seismic surveys.
Sonars are devices that emit sounds to detect and locate objects using the returning echo. There are two types of sonars: passive and active. Active sonars are primarily used by the military and can cause hearing loss in fish and whales to lose their way.
With shipping increasing massively in recent decades, ocean noise pollution has doubled every decade since the 1960s. The constant noise generated by vessels can interfere with the communication of marine mammals and increase their stress levels.
Seismic surveys are used to map offshore oil and natural gas fields by blasting powerful air guns at 10-second intervals and measuring the echoes off the seafloor. These blasts can severely damage the internal organs of marine animals and kill zooplankton within a 1.2 km radius.
Marine mammals and other aquatic animals have evolved to use underwater sound as a primary means of communication and assessing their environment. Noise pollution can interfere with these critical activities, causing temporary or permanent hearing loss, behavioural and physiological changes, and even death.
