The Hidden Menace: Ocean Noise And Marine Life

Marine life is heavily impacted by noise pollution, which has increased dramatically in recent decades. As sound travels faster in water than in air, human activities such as shipping, boating, and energy exploration have led to rising noise levels that interfere with marine animals' ability to hear and communicate. This disruption can affect their vital functions, including mating, finding prey, and avoiding predators, ultimately threatening their survival and causing behavioural changes and even death. The problem is especially acute for whales and dolphins, which are highly sensitive to naval sonar and suffer fatal strandings as a result. With noise pollution causing far-reaching consequences for marine ecosystems, it is crucial that we address this issue to enable the recovery of marine life.

Communication difficulties

Marine life relies heavily on sound for communication, and noise pollution can severely disrupt this. The problem is not the sound itself, but when sound becomes "noise". The impact of noise depends on the species' sensitivity threshold and the type of impact generated, such as disturbances, avoidance, or damage.

Noise pollution can interfere with the detection of acoustic signals, masking the sounds produced by marine wildlife. This leads to changes in individual and social behaviour, altered metabolisms, and hampered population recruitment, which can affect the health and function of marine ecosystems. For example, increased ship noise has caused bottlenose dolphins to simplify their vocal calls, potentially reducing the information content of their calls and decreasing effective communication.

Noise can also cause marine mammals to change their vocal behaviour. They may compensate for noise by making their signals longer, increasing the volume of their calls, shifting their sound frequency, or waiting until the noise has stopped to signal. However, these changes can be costly.

Noise pollution can also reduce the communication range of marine mammals. This can have a negative impact on reproduction, as acoustic communication often plays a crucial role in the reproductive interactions of marine life. A 2017 study found that male fish exposed to continuous additional noise engaged in less acoustic courtship, and were less likely to spawn successfully.

Underwater noise can lead to reduced communication in whales and dolphins, which can negatively impact their reproduction. It can also delay their migration, causing them to become trapped in ice and die.

Hearing loss

Marine animals depend on their hearing for survival. Sound is critical for communication, navigation, locating prey, avoiding predators, and finding mates. Hearing is also essential for sensing their environment and orientation. However, noise pollution from human activities such as shipping, boating, and energy exploration has led to increased noise levels in coastal and offshore habitats, negatively impacting marine life.

The rising noise levels in the oceans have severe implications for the hearing capabilities of marine animals. Noise pollution can induce both temporary and permanent hearing loss in marine mammals and other species. The degree of hearing loss depends on the intensity and duration of the noise exposure. Explosive sounds from activities like hydrocarbon exploration can cause marine animals to avoid certain areas, even if they were previously important for calving or feeding.

Research has shown that temporary or permanent hearing impairment in marine mammals leads to a decrease in their overall well-being. Their foraging efficiency, reproductive potential, social interactions, and ability to detect predators are all negatively impacted. For example, a seismic airgun was observed to damage fish ears, and recovery took more than 58 days. In another instance, naval sonar led to fatal strandings of whales and dolphins, likely due to decompression sickness.

The impact of hearing loss in marine life goes beyond the individual level. Noise pollution can cause changes in the behaviour of entire populations, affecting their breeding habits and migration patterns. For instance, noise from ferries caused tuna schools to become uncoordinated, which could impact the accuracy of their migrations. Additionally, embryo development in sea hares was impaired, and larvae suffered increased mortality when subjected to boat noise.

Stress and behavioural changes

Noise pollution in the ocean has increased dramatically over the past few decades, threatening the natural soundscape of marine environments. This has various effects on marine life, including stress and behavioural changes.

Marine animals are highly dependent on sound for survival. They use sound to communicate, locate mates and prey, avoid predators, navigate, and defend their territories. Noise pollution interferes with these key life functions, causing stress and behavioural changes.

Anthropogenic noise can cause a stress response in marine animals, increasing their risk of mortality and interfering with sound-based orientation and communication. It can also lead to physiological changes, such as increased metabolism and reduced immunity.

Noise pollution can also alter the behaviour of marine animals. They may move away from the noise source, adjust their activities to avoid noisy times, or increase their anti-predatory behaviour. For example, seismic tests in the North Atlantic caused local fish catch rates to drop by up to 70%.

Noise can also disrupt feeding, breeding, nursing, and communication behaviours. For instance, sonar has been recorded to alter the feeding behaviour of endangered blue whales, causing them to stop feeding, increase their swimming speed, and move away from the sound source. This can have significant impacts on their individual fitness, foraging ecology, and population health.

Additionally, noise pollution can cause auditory masking, where biologically important sounds are drowned out or distorted by the polluting noise. This can result in reduced or ineffective communication and the transmission of misleading information.

Reproduction and breeding issues

Noise pollution in the ocean has increased dramatically over the last few decades, threatening the natural soundscape of the marine environment. As most marine species are highly dependent on sound for their survival, this type of pollution is extremely damaging to marine wildlife.

Anthropogenic noise can interfere with the detection of acoustic signals in the marine environment, which can lead to changes in individual and social behaviour, altered metabolisms, and hampered population recruitment. This, in turn, can affect the health and service functions of marine ecosystems.

Noise pollution can also decrease the communication range of marine mammals and cause them to change their vocal behaviour. For example, increased ship noise caused bottlenose dolphins to simplify their vocal calls. Higher dolphin whistle frequencies and a reduction in whistle complexity were recorded, and it’s possible that this simplification may reduce the information content of their calls and therefore decrease effective communication.

Marine mammals may also compensate for noise by making their signals longer, increasing the volume of their own calls, shifting their sound frequency, or waiting to signal until the noise has gone. However, these changes can be costly.

Noise can also affect the reproduction of other marine species. For example, cod broodstock exposed to noise resulted in higher cortisol in the resulting eggs, which lowered the fertilization rate by 40% and viable egg productivity by 50%, translating to a loss of about 300,000 weaned juvenile cod.

Migration disruption

Marine life relies on sound to navigate, communicate, and hunt. Noise pollution interferes with these activities, causing migration disruption, behavioural changes, and even mortality.

Marine mammals, such as whales, depend on their ability to communicate across vast distances to navigate during migration. For example, whale vocalizations allow them to find food, travel along coastlines safely, and stay connected with their pods. Noise pollution can mask these vocalizations, causing whales to become disoriented and disrupting their migration routes. This disorientation can lead to strandings, where whales become stranded on beaches, resulting in injury, stress, and even death.

The increase in ship traffic has led to a "doubling [of] noise intensity" in the ocean every ten years. This rise in noise pollution has been shown to disorient schools of bluefin tuna during their migration. It is not just shipping that causes this problem; seismic air gun surveys, often used by the oil and gas industry to map the seafloor, can also displace fin whales and kill zooplankton.

Marine life is also impacted by pile driving, the act of pounding structures into the seabed to support constructions like offshore wind farms. This activity has been known to stress out blue mussels and sea bream and disturb the swimming and schooling behaviour of cod and sole, further contributing to migration disruption in marine life.

Overall, noise pollution has far-reaching consequences for marine life, and measures must be taken to reduce and mitigate its impacts to protect the fragile ecosystems of our oceans.

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