Ocean Noise Pollution: Who Suffers?

Ocean noise pollution is a growing problem that affects a wide range of marine animals. Human activities such as commercial shipping, oil exploration, seismic surveys, offshore wind turbine installation, and military sonar have caused unnatural and excessive sound to be generated underwater. This noise pollution can interfere with marine animals' natural behaviours and their ability to communicate, navigate, locate prey and avoid predators. All marine life is impacted by ocean noise to some extent, with marine mammals like whales and dolphins being particularly affected. Noise pollution has also been linked to mass strandings of whales and, in some cases, even death.

Marine mammals

Noise pollution can cause marine mammals to panic, leading to decompression sickness and tissue damage from gas bubble lesions. It can also cause hearing loss and, in some cases, death. Noise from naval sonar devices, ships, seismic surveys, explosions, construction, and sonar devices have made the ocean a loud and chaotic environment for these animals.

Noise pollution can also interfere with the detection of acoustic signals, leading to changes in individual and social behaviour, altered metabolisms, and hampered population recruitment. It can decrease the communication range of marine mammals and cause them to change their vocal behaviour. For example, increased ship noise has caused bottlenose dolphins to simplify their vocal calls, which may reduce the effectiveness of their communication.

Some marine mammals may compensate for noise by making their signals longer, increasing their volume, shifting their sound frequency, or waiting until the noise has stopped to signal. However, these changes can be costly.

Overall, noise pollution has been shown to have negative effects on marine mammals, and it is vital that we reduce our impacts through policies and the development of quieter technologies.

Fish and invertebrates

Noise pollution can cause developmental issues in fish and invertebrates, including body malformations, higher egg or immature mortality, developmental delays, and slower growth rates. It can also affect their ability to reproduce and feed. For example, some commercial fish catches have dropped by up to 80% due to noise, as larger fish tend to leave the area.

Invertebrates, in particular, are sensitive to particle motion rather than sound pressure. They are often affected by substrate vibrations, which usually involve particle motion. Sources of marine underwater noise that generate vibration include shipping, oil and gas exploration, and construction.

Noise pollution can also affect the ecological services performed by invertebrates, such as water filtration, mixing sediment layers, and bioirrigation, which are key to nutrient cycling on the seabed.

Research has shown that noise pollution can cause physiological changes in fish and invertebrates, including increased levels of stress hormones, metabolic rate, oxygen uptake, cardiac output, and mortality rate. It can also lead to cellular damage and hearing loss.

Overall, noise pollution has been shown to have significant negative impacts on fish and invertebrates, affecting their behaviour, reproduction, and survival.

Echolocation

However, ocean noise pollution caused by human activities such as commercial shipping, oil exploration, seismic surveys, and military sonar is interfering with the natural sounds in the ocean. This pollution is causing excessive and unnatural sound levels that can obscure the natural sounds that marine animals rely on for communication and survival.

For animals that use echolocation, like dolphins and toothed whales, ocean noise pollution can disrupt their signals, causing them to become disoriented and unable to hunt successfully. The loud noises can also induce panic, causing them to ascend too quickly to escape the noise, which can lead to decompression sickness and even death.

The impact of ocean noise pollution on echolocation is not limited to dolphins and toothed whales. Other marine mammals, such as the North Atlantic right whale, also experience increased stress levels due to the constant noise generated by vessels. Additionally, seismic activities used to search for oil and gas deposits can emit deafening noise pulses that disrupt the natural behaviours of marine mammals, causing them to flee or even suffer fatal injuries.

To address the issue of ocean noise pollution affecting echolocation, there have been efforts to establish regulations and guidelines. The International Maritime Organization (IMO), for example, has developed guidelines for reducing underwater noise from shipping. These guidelines include strategies such as ship speed reduction and technical innovations in shipbuilding. Despite these efforts, there are still no international legal regulations specifically addressing ocean noise pollution.

Ocean ecosystems

Marine mammals, such as whales, dolphins, and porpoises, are highly dependent on sound for vital life functions, including communication, locating food and mates, navigating, and avoiding predators. Noise pollution interferes with their natural behaviours and ability to communicate, disorienting them and even causing hearing loss or death. For example, naval sonar, which works similarly to echolocation used by whales and dolphins, has been linked to mass strandings of beaked whales.

The impact of noise pollution on marine mammals can also have indirect effects on other species in the ecosystem. For instance, if a whale strands on a beach due to noise pollution and dies, the seafloor-dwelling animals that rely on its body as a food source are subsequently affected.

Fish, invertebrates, and even zooplankton are also impacted by noise pollution. It can trigger stress responses in fish, disrupt nesting habits, affect coordination and navigation, and damage hearing. Seismic surveys, for instance, can kill zooplankton within a 1.2-kilometre radius and severely damage the internal organs of giant squid.

Noise pollution in the ocean has increased dramatically in recent decades, with shipping being a major contributor. The bigger and faster a ship is, the louder it tends to be. Global shipping has increased significantly, with up to 90% of internationally traded goods now transported by sea, leading to a doubling of noise pollution in many marine areas every decade since the 1960s.

To protect ocean ecosystems, efforts are being made to reduce noise emissions. For example, the International Maritime Organization (IMO) is working on revising guidelines to reduce noise emissions from shipping, and organizations like IFAW and OceanCare are advocating for regulations and speed reductions for ships to lessen their acoustic impact on marine life.

Human activities

Commercial Shipping

Commercial shipping is a major contributor and the most common source of noise pollution in the oceans. Most of the underwater noise is caused by a ship's propeller cavitation—the bubbles that are generated and implode due to excessive propeller speed. Hull vibrations and vessel diesel engines also contribute significantly to the noise. Globally, just about 15% of the global fleet accounts for half of the noise emissions caused by shipping.

Sonars

Sonars are devices that emit sound waves to detect objects underwater. There are two types of sonars: passive and active. Passive sonars listen for underwater sounds, while active sonars emit sounds to detect objects using the returning echo. Active sonars are primarily used by the military but also by commercial ships, the fishing industry, and marine research organizations. The use of active sonars has been linked to whale strandings and changes in the feeding behaviour of blue whales.

Construction Activities

Construction activities such as dredging, platform installation, drilling, and pile driving during the construction of offshore wind farms generate massive amounts of noise emissions. The continuous use of machinery and transport that emit loud noise at low frequencies disrupts the ocean's flora and fauna.

Seismic Surveys

Seismic surveys are used to gather information about the characteristics and locations of geological structures under the ocean's surface, often to identify areas with oil and gas deposits. This process involves the use of seismic air guns that emit loud, continuous blasts of sound waves, which can last from seconds to months. These blasts can interfere with the communication of marine animals and have been linked to injuries and deaths.

Military Activities

Military activities, including the use of active sonars and detonations, are among the biggest contributors to ocean noise pollution. The use of active sonars by navies to detect submarines has been linked to whale strandings and changes in the behaviour of marine mammals. Detonations from weapon tests, the explosion of old ammunition, and other military activities generate extremely powerful noise across a wide range of frequencies.

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