Human Impact: Ocean Noise Pollution Sources

Marine animals have evolved over millions of years to use underwater sound as a primary means of communication and survival. However, human activities such as commercial shipping, military sonar, oil exploration, seismic surveys, and construction have led to a significant increase in ocean noise pollution, causing detrimental effects on marine life. This noise pollution can interfere with marine animals' natural behaviours and communication, leading to disorientation, stress, and even injury or death. With ocean traffic and human presence in the oceans increasing, addressing noise pollution and its impact on marine ecosystems has become crucial.

Commercial shipping

The international commercial fleet numbers more than 100,000 ships. A cargo vessel emits around 190 decibels of noise, which is louder than a jet engine at takeoff and about the same noise level as a rock concert. Noise travels fast in water—four times faster than in air—meaning that noise from a ship can carry exceedingly far, impacting a broad swath of the ocean as it travels.

Most of the underwater noise emitted by ships comes from propeller cavitation, which is a complex phenomenon that can be boiled down to a design issue that causes a breakdown in water flow over the propeller blades, resulting in significant noise (and a loss in fuel efficiency). Solutions to cavitation include design changes to the propeller and the hull of the ship, or the use of new devices that smooth water flow into the propeller. In 2017, the shipping company Maersk modified several of its ships by installing efficient propellers and reconfiguring hulls, and found these improvements resulted in a 75% reduction in noise energy emitted from the ship.

The International Maritime Organization (IMO) is working on the revision of the guidelines for the reduction of noise emissions from shipping. Technical innovations and adaptations in shipbuilding are also being taken into account. The revised guidelines are expected to be issued in the summer of 2023. Russell Leaper, an IFAW consultant and noise expert, has calculated that reducing the speed of the global shipping fleet by 10 or 20% would reduce noise emissions by 40 or 67% respectively.

Military activities

The use of sonar and seismic air guns by the military is of particular concern. These devices emit high-intensity and excessively loud sounds that can cause panic in marine animals, leading to erratic behaviour and even injury. For example, animals may ascend too quickly to escape the noise, resulting in decompression sickness and skin damage from gas bubble lesions.

Noise pollution from military activities can also interfere with the natural behaviours and communication of marine mammals. It can obscure their ability to hear natural sounds in the ocean, disrupting their ability to navigate, forage, and maintain social structures. This is especially problematic for animals that rely on echolocation, such as dolphins and toothed whales, as excessive noise can disorient them and impact their hunting abilities.

Furthermore, military activities can contribute to the overall increase in background noise in the ocean, which has doubled in many marine areas since the 1960s. This "acoustic fog" can mask the communication of marine mammals, such as whales, and lead to increased stress levels. Research has shown that vessel traffic in Glacier Bay National Park has caused substantial communication losses for singing and calling whales, as well as roaring seals.

Noise pollution from military activities has severe and deadly impacts on marine life. It can cause hearing loss, alter breathing rates, and even lead to strandings and death. The complex and interconnected nature of ocean ecosystems means that the effects of noise pollution on one species can have indirect consequences on others. For example, the stranding and death of a whale on a beach due to sudden, intense noise can deprive seafloor-dwelling animals of a key food source.

Oil and gas exploration

The noise created by air guns can travel thousands of kilometres and has been detected as far as 4,000 kilometres away. Humpback whales, in particular, are affected by these noises, with research indicating behavioural changes and deterrence from their migration routes. The noise can interfere with their communication, which relies on loud sounds that can travel over long distances underwater.

The impact of air gun usage is not limited to whales. It can also cause severe damage to the internal organs of giant squid and even lead to the death of juvenile krill and zooplankton. This disruption in the ecosystem can have far-reaching consequences, affecting various species that depend on these organisms for food and sustenance.

Noise from oil and gas exploration is considered a form of marine pollution and is recognised as an invisible threat to marine life. It can result in hearing loss, stress, and physical injury to marine animals. The constant loud noises can also lead to habitat loss, reduced reproduction rates, and impairment of the immune system in affected species.

To address this issue, there have been calls for regulations to reduce the impact of noise on marine life. The International Maritime Organization (IMO) is working on revising guidelines for noise emission reduction, including considering technical innovations and adaptations in shipbuilding. These efforts aim to minimise the harmful effects of oil and gas exploration activities on the delicate marine ecosystem and the animals that depend on it.

Construction

Port construction work, in particular, has been identified as a significant source of noise pollution. The building and expansion of ports often involve extensive construction activities, including dredging, drilling, and pile driving, which produce high levels of noise that propagate through the water. These noises can mask the vocalizations of marine animals, making it difficult for them to communicate, find food, and navigate their environment.

Additionally, the construction and operation of offshore oil and gas drilling platforms contribute to noise pollution. The use of heavy machinery, such as seismic air guns and pile drivers, creates intense noise emissions that can disrupt the natural behaviours of marine mammals and even cause hearing loss. The noise generated by these activities can spread over vast distances in the water, affecting a wide range of marine species.

To mitigate the impact of construction-related noise pollution on marine life, several measures can be implemented. These include adopting quieter technologies, such as "bubble curtains" to muffle construction noise, and implementing policies that mandate acoustic mitigation in marine environments. The International Maritime Organization (IMO) has established guidelines for reducing underwater noise from shipping, which include strategies for noise reduction in design, construction, and operation, such as reducing ship speeds.

It is important to recognize that construction-related noise pollution is a human-induced issue. By taking proactive steps to reduce noise emissions during construction projects, especially those near or within marine environments, we can help minimize the negative impacts on marine life and enable their recovery.

Seismic surveys

The noise from seismic surveys can have detrimental effects on marine life. Studies have shown that seismic survey noise can cause a decrease in cetacean sightings, with some species being more affected than others. For example, baleen whales are more vulnerable to disturbance from seismic airgun noise than toothed whales due to the overlap with the frequency ranges of their communication signals and hearing sensitivities.

The impact of seismic surveys on other marine life has also been studied. One study found that zooplankton populations dropped by 64% within an hour of an airgun blast, and there were also more dead zooplankton recorded as far away as 0.7 miles. Another study found that seismic surveys negatively affected humpback whale singing activity off the coast of northern Angola.

In addition to the direct impacts on marine life, seismic surveys can also have indirect effects. For example, if a whale strands on a beach in response to a sudden loud noise from a seismic survey, it dies on land instead of at sea. This means that sea-floor-dwelling animals that rely on the whale's body for food will lose a key food source.

Due to the potential impacts on marine life, there have been increasing concerns and calls for action to address the noise pollution caused by seismic surveys. Some countries have started to take a harder look at airgun noise, with Mexico and Brazil implementing restrictions on survey permits and locations. However, worldwide awareness of the long-range acoustic effects of these surveys is still developing, and there are currently no international standards for the regulation of ocean noise pollution.

Frequently asked questions