Helena Joyce
Underwater noise pollution is a pressing issue that has gained prominence in recent years. It refers to the excessive and unnatural sounds caused by human activities such as shipping, industrial fishing, oil drilling, seismic surveys, and military sonar, which negatively impact marine life. Marine animals, such as whales, dolphins, and fish, rely on sound for communication, navigation, and survival. The introduction of human-made noise can interfere with these vital functions, leading to behavioural changes, hearing loss, and even death. Scientists from organizations like NOAA Fisheries, OceanCare, and IFAW are actively studying the effects of underwater noise pollution using passive acoustic techniques, autonomous technology, and tagging experiments. Their research aims to understand the impact of noise on specific species, set noise reduction targets, and guide policy interventions to protect marine ecosystems and mitigate the harmful consequences of human-induced noise pollution in our oceans.
| Characteristics | Values |
|---|---|
| How scientists study underwater noise pollution | By using passive acoustic techniques, autonomous technology, and underwater microphones or acoustic recorders to listen to and record ocean sounds |
| Noise sources | Shipping, industrial fishing, coastal construction, oil drilling, seismic surveys, warfare, sea-bed mining, sonar-based navigation, terrestrial traffic, dredging technology, naval sonar devices, seismic airguns, offshore wind turbine installation, dynamite fishing, controlled detonation of bombs, cargo ships, and climate-friendly activities |
| Impact on marine life | Interference with key life functions, temporary or permanent hearing loss, behavioural and physiological changes, masking, injury, and death |
| Affected marine life | Marine mammals, marine animals, cetaceans (whales, dolphins, and porpoises), fish, and invertebrates |
| Solutions | Reducing vessel speed, setting targets for noise reduction, preventing noise levels from reaching harmful thresholds, protecting diverse and biologically important marine regions, and following guidelines established by the International Maritime Organization (IMO) for noise reduction in ship design, construction, modification, and operation |
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What You'll Learn
Impact on marine life
Marine animals have evolved over millions of years to use underwater sound as a primary means of communication and assessing their environment. Sound plays an essential role in critical activities such as breeding, foraging, maintaining social structure, and avoiding predators. Therefore, noise pollution can have a significant impact on marine life.
Marine mammals and other aquatic animals, such as fish and invertebrates, are highly dependent on underwater sound for survival. They use sound to communicate, locate mates and prey, navigate, and avoid predators. Noise pollution can interfere with these key life functions and even cause death. For example, excessively loud sounds, like those produced by seismic blasts used for oil and gas exploration, can cause hearing loss in cetaceans (whales and dolphins). More continuous or chronic noises can mask communication and the ability of animals to hear and avoid danger, increasing the risk of ship strikes or separation from their calves or pod.
The sources of human-produced underwater noise pollution are diverse and numerous, including shipping, industrial fishing, coastal construction, oil drilling, seismic surveys, warfare, sea-bed mining, sonar-based navigation, and even climate-friendly activities such as offshore wind farms. Shipping alone has contributed an estimated 32-fold increase in low-frequency noise along major shipping routes in the past 50 years, driving marine animals away from vital breeding and feeding grounds.
The impact of noise pollution on marine life can be immediate and severe, or it may accumulate over time. For example, the controlled detonation of bombs dropped on the seafloor during World War II continues to be a major source of disruptive and destructive sound in the North Sea. Even terrestrial traffic, such as bridges or coastal airports, can produce low-level continuous noise that penetrates underwater.
Noise pollution can also affect marine life in more subtle ways, such as disrupting the natural behaviour of marine mammals and causing them to leave noisy areas, further shrinking their habitat and undermining conservation efforts. The good news is that, unlike other forms of pollution, the impact of noise pollution can be reversed relatively quickly. During the COVID-19 lockdown in 2020, ocean noise levels decreased by 20%, and marine life was observed returning to once-busy waterways, claiming back their ancestral territory.
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Human activities causing noise
Marine animals have evolved over millions of years to use underwater sound as a primary means of communicating and assessing their environment. Sound plays a crucial role in critical activities for marine species, such as breeding, foraging, maintaining social structure, and avoiding predators. However, human activities have increasingly become a source of noise pollution in the oceans, disrupting the natural soundscape and impacting marine life.
One significant contributor to underwater noise pollution is shipping and naval activities. The use of propellers and engines in ships and boats generates noise that penetrates deep into the ocean. This noise can interfere with the natural sounds used by marine animals for communication and navigation. In addition, naval vessels conducting sonar-based navigation and searches for oil and gas sources further contribute to the underwater noise levels.
Offshore construction and infrastructure development also generate significant noise pollution. The use of heavy machinery, drilling, and pile-driving can create loud and continuous noises that disrupt the natural acoustic environment of marine species. This includes the construction of wind farms, which, despite being considered climate-friendly, can substantially increase local sound levels.
Oil and gas exploration and extraction activities are another major source of underwater noise pollution. Seismic surveys, for example, utilize sonic cannons to pound the seafloor, creating vibrations that can travel miles deep. Additionally, underwater drilling operations generate noise that can interfere with the acoustic cues used by marine animals.
Other human activities that contribute to underwater noise pollution include recreational boating, dynamite fishing, and seabed mining. These activities introduce abrupt and intense sounds that can startle marine animals and disrupt their natural behaviours. Even terrestrial traffic, such as vehicles on bridges or coastal airports, can produce low-level continuous noise that penetrates underwater.
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Technologies for studying noise
NOAA Fisheries studies marine animals by using a range of technologies to record underwater ocean sounds. They also provide technical support and advice on the management and assessment of protected species and anthropogenic impacts.
Other technologies used to study underwater noise pollution include seismic airguns, which are used to search for oil and gas under the seabed and can generate up to 260 decibels of noise every 10 to 15 seconds. Cargo ships can emit noise levels of up to 190 decibels, which is much louder than a plane taking off. The speed of ships also plays a role, with faster and larger ships tending to be louder. Reducing the speed of the global shipping fleet by 10-20% can result in a noise emission reduction of 40-67%.
Underwater noise pollution has been found to interfere with the key life functions of marine mammals, including communication, breeding, foraging, and maintaining social structures. It can also cause temporary or permanent hearing loss, behavioural and physiological changes, masking of natural sounds, injury, and even death.
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Noise thresholds for marine animals
Marine animals have evolved over millions of years to rely on underwater sound as a primary means of communication and assessing their environment. Sound plays an essential role in critical activities such as breeding, foraging, maintaining social structure, and avoiding predators. For example, cetaceans (whales, dolphins, and porpoises) send and receive complex sounds to communicate with each other, navigate the water, and find food.
The impact of ocean noise on the efficiency of sound-travel underwater and the overall well-being of marine species is a growing concern. Human-caused sounds can affect animals in various ways, and the impacts can be immediate or accumulate over time. Excessively loud sounds, like those from seismic blasts used for oil and gas exploration, can cause temporary or permanent hearing loss in cetaceans. Continuous or chronic noises can mask communication and the ability of animals to sense their environment, avoid danger, and find food, potentially putting them at greater risk of ship strikes or separation from their calves or pod.
NOAA Fisheries studies marine animals by using a range of technologies to record underwater ocean sounds. They use passive acoustic techniques, autonomous technology, and other means to research the effects of human-made sounds on marine mammals' abilities to hear and navigate.
Scientists have been studying noise-induced hearing loss in marine mammals through temporary threshold shift (TTS) experiments. These experiments involve exposing marine mammals to increasing levels of noise to determine the exposure parameters necessary to cause TTS and observe any threshold shifts. The basic experimental approach is similar to that used for terrestrial mammals, starting with a pre-exposure hearing threshold measurement, followed by the fatiguing sound exposure. If the hearing threshold does not fully recover, the remaining noise-induced threshold shift (NITS) is called a permanent threshold shift (PTS). Extensive studies of NITS in humans and small terrestrial mammals have helped develop safe exposure guidelines for people working in noisy environments.
Noise levels in some parts of the ocean are more than a hundred times louder than they would be naturally due to human activities such as shipping, industrial fishing, coastal construction, oil drilling, seismic surveys, warfare, seabed mining, and sonar-based navigation. Even climate-friendly activities like offshore wind farms can substantially increase local sound levels. The effects of underwater noise pollution are visible in well-studied marine mammals and increasingly documented in fish, invertebrates, and other species.
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Strategies to reduce noise
Strategies to reduce underwater noise pollution include:
Reducing the speed of ships
Shipping is one of the most significant contributors to underwater noise pollution. Slower ships produce less noise, with a 10-20% reduction in speed leading to a 40-67% reduction in noise emissions. Adjusting ship schedules to allow for longer quiet intervals between ship noise events can also help.
Reducing the use of seismic airguns
Seismic surveys are used to map the seafloor and locate oil and gas fields, but they involve blasting loud noises into the ocean. Airguns used in these surveys emit noises of up to 260 decibels every 10-15 seconds. By reducing the use of seismic airguns, noise emissions can be significantly lowered.
Protecting and restoring natural soundscapes
Natural soundscapes, such as the sounds of waves, wind, and marine life, are being drowned out by human-made noise. In areas that are already dominated by human-made noise, setting targets for noise reduction is essential. Additionally, in regions that are experiencing rapid industrial development and marine transportation growth, preventing noise levels from reaching harmful thresholds is crucial.
Reducing the use of destructive fishing practices
Dynamite fishing, for example, is a major source of blasting noise in Southeast Asia and coastal Africa. Other destructive fishing practices, such as the use of certain types of gear, can also contribute to underwater noise pollution. By eliminating or reducing these practices, noise pollution can be mitigated.
Implementing noise reduction measures in marine protected areas
Designating and protecting biologically important marine regions from noise pollution is essential. For instance, the waters between the Balearic Islands and the Spanish mainland have been established as a marine protected area, safeguarding them from seismic surveys and the associated noise pollution.
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Frequently asked questions
Underwater noise pollution is a form of environmental pollution caused by human activities—like commercial shipping, oil exploration, seismic surveys, offshore wind turbine installation, and military sonar—that generate unnatural and excessive sound underwater.
Marine mammals like whales, dolphins, and porpoises are particularly affected by underwater noise pollution as they rely on sound to communicate, locate mates and prey, avoid predators, navigate, and even defend their territories. Noise pollution can interfere with these key life functions, causing behavioural and physiological changes, injury, and even death.
Scientists use passive acoustic techniques, autonomous technology, and other means to research the effects of sounds made by human activities on marine life. They also study marine animals by using a variety of technologies to record underwater ocean sounds.
