Underwater Noise Pollution: Which Animals Are Affected?

Underwater noise pollution is a growing issue that threatens marine wildlife and the health of the ocean. It is caused by human activities such as shipping, seismic surveys, oil exploration, military sonar, and construction, which have increased dramatically over the past few decades. This noise pollution interferes with the key life functions of marine animals, such as communication, navigation, locating prey, avoiding predators, and finding mates. It can cause behavioural and physiological changes, hearing loss, injury, and even death. All marine species are affected by underwater noise pollution, from the smallest plankton to the largest whale, and it is important to raise awareness and take action to reduce this type of pollution and mitigate its impacts on marine life and ecosystems.

Ocean noise from ships

The oceans are predominantly an acoustic world, as light only penetrates to a depth of 200 meters, and there is no light beyond 1,000 meters. Marine animals, from plankton to whales, depend on sound for vital functions such as mating, finding prey, avoiding predators, sensing their environment, orientation, and communication.

Noise from ships can disrupt these functions, causing marine animals to leave their preferred habitats and change important behaviours. For example, ship noise has been observed to affect the singing of mates, foraging for food, and nursing of babies. It has also been linked to elevated stress levels in marine mammals, reducing their resilience to other challenges such as water pollution and climate change.

Hundreds of studies have demonstrated the adverse impacts of ship noise on marine species. For instance, increased stress hormones have been observed in critically endangered North Atlantic right whales, affecting their reproduction and immunity. Southern Resident orcas, who already face scarce prey resources, have shown reduced foraging behaviour due to ship noise. Narwhals become motionless, sink, and fall silent at relatively low noise levels.

To address this issue, measures such as ship design changes, ship maintenance, and policy solutions have been proposed. Quieter propellers, engine insulation, and slower shipping speeds can help reduce underwater noise. While voluntary guidelines for noise reduction have been created by the International Maritime Organization, mandatory measures are needed to ensure industry-wide action to protect ocean wildlife.

Ocean noise from oil exploration

Marine animals, such as whales and dolphins, rely heavily on sound for vital functions such as mating, finding prey, and navigation. The loud noises from oil exploration can interfere with these functions, causing stress and driving animals out of their habitats. It can also lead to hearing loss, behavioural changes, and even death.

In recent years, there has been an increase in the number of dolphin strandings, which has been linked to offshore oil exploration. Oil companies often use sonar or acoustic soundings to detect oil deposits beneath the seafloor, and the loud noises produced by these technologies can disorient dolphins and whales, causing them to become stranded on shores.

Toothed whales, including dolphins and porpoises, have evolved to use echolocation for navigation and hunting. The loud noises from oil exploration can disrupt their echolocation abilities, making it difficult for them to navigate and find food.

Regulations and policies are needed to reduce the impact of ocean noise from oil exploration on marine life. This includes taking into account not just the loudness of the noise but also the distance it travels. Additionally, more research is required to fully understand how ocean mining noise affects the migration routes of whales and other marine species.

Ocean noise from military sonar

Sonar systems were first developed by the U.S. Navy to detect enemy submarines and can generate sound waves of up to 235 decibels, which is much louder than the world's loudest rock bands, which top out at 130 decibels. These sound waves can travel for hundreds of miles under water and retain an intensity of 140 decibels as far as 300 miles from their source.

The loud and far-reaching noise from military sonar can cause serious harm to marine wildlife. Whales, dolphins, and other marine species have been observed to exhibit abnormal behaviour in response to sonar, such as rapidly changing their depth, swimming away from the noise source, or even beaching themselves. In some cases, exposure to sonar has led to physical injuries and death among marine animals.

The use of military sonar has been linked to mass strandings of beaked whales and other species. In one incident, 34 whales of three different species died along North Carolina's Outer Banks during Navy sonar training nearby. Environmental groups have campaigned to ban or restrict the use of sonar in waters rich in marine wildlife, citing the potential for serious harm to marine mammals.

The impact of military sonar on marine life is a complex issue. While it is important for national security, efforts should be made to minimize its impact on marine wildlife. This includes implementing policies to reduce propeller noise from ships, using quieter technologies, and gradually ramping up testing to give marine animals a chance to flee affected areas.

Ocean noise impacts on whales

Ocean noise has a variety of impacts on whales, from behavioural changes to hearing loss and even death.

Whales rely on sound to communicate, locate mates and prey, avoid predators, navigate, and defend their territories. As such, noise pollution can interfere with their key life functions. For example, noise can cause whales to alter their feeding behaviour, as seen in an experiment where blue whales stopped feeding, increased their swimming speed, and moved away from the sound source. It can also cause whales to change their vocal behaviour, with bottlenose dolphins simplifying their vocal calls in response to increased ship noise.

Noise pollution can also cause hearing loss in whales, with loud man-made noises linked to mass breaching events around the world. Naval sonar devices are particularly harmful, with their loud, mid-frequency sounds linked to mass strandings of beaked whales. These strandings can lead to decompression sickness and even death.

Noise can also cause behavioural changes in whales, such as moving away from the noise source, adjusting their activities to avoid noisy times, or increasing their anti-predatory behaviour. It can also cause stress in whales, with the build-up of stress-related chemicals linked to growth suppression, lower fertility, and poor immune system function.

In addition, noise can delay whale migration, causing them to become entrapped in ice and die. It can also disrupt their ability to communicate, navigate, and hear critical sounds from predators and prey, a phenomenon known as "masking". This is especially notable in areas with heavy human use, such as commercial shipping lanes and busy ports.

The impacts of ocean noise on whales are complex and far-reaching, affecting their health, reproductive success, and survival.

Ocean noise impacts on fish

Ocean noise pollution, caused by human activities such as commercial shipping, seismic surveys, oil exploration, and military sonar, has severe impacts on marine life, including fish. Sound is the primary means of communication for many marine species, and ocean noise disrupts their key life functions, affecting their ability to communicate, navigate, locate prey, avoid predators, and reproduce.

Impact on Fish Development and Anatomy

Ocean noise has been found to cause developmental issues in fish, including body malformations, higher egg or immature mortality, developmental delays, delays in metamorphosing and settling, and slower growth rates. It also causes massive internal injuries, cellular damage to statocysts and neurons, resulting in disorientation and even death. Hearing loss is another consequence, and the damage to hearing structures can worsen over time, even after the noise exposure has ceased.

Stress and Behavioural Changes

Noise pollution induces stress in fish, leading to increased levels of stress hormones, greater metabolic rates, oxygen uptake, cardiac output, parasites, irritation, distress, and mortality rate. It can also trigger alarm responses, increased aggression, hiding, and flight reactions. Their anti-predator defence mechanisms, nest digging, and nest care behaviours are reduced. Noise causes distraction, leading to food-handling errors, decreased foraging efficiency, and greater vulnerability to predation. Schooling fish become uncoordinated and unstructured due to noise, affecting their communication and coordination.

Impact on Reproduction and Feeding

Noise pollution disrupts the reproductive behaviours of fish, including reduced courtship calls, spawning, and egg clutches. It also affects their feeding behaviours, with decreased foraging efficiency and increased vulnerability to predation. These impacts on reproduction and feeding compromise the overall health and viability of fish populations.

Impact on Commercial Fishing

The presence of noise can cause commercial catch rates to drop by up to 80%, as larger fish tend to leave the noisy areas. Bycatch rates may also increase, and abundance generally decreases. These impacts not only affect the fisheries but also have socioeconomic consequences for local fishermen.

Impact on Ecological Services

Invertebrates play a crucial role in providing ecological services such as water filtration, mixing sediment layers, and bioirrigation, which are essential for nutrient cycling on the seabed. Noise pollution negatively affects their ability to perform these functions, compromising the health and productivity of the ecosystem.

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