Noise, Light Pollution: Impact On Our Hydrosphere

The hydrosphere, encompassing all aquatic environments, is under threat from noise and light pollution. With over half of the world's population living near coastal or freshwater ecosystems, human activities are increasingly impacting the health of these environments. Noise and light pollution, caused by shipping, boating, construction, seismic surveys, and artificial lighting, are detrimental to the hydrosphere and the organisms that inhabit it. These forms of pollution interfere with the natural behaviours and survival strategies of aquatic life, threatening the delicate balance of aquatic ecosystems. Understanding the impact of noise and light pollution on the hydrosphere is crucial for developing effective conservation strategies and preserving the biodiversity that depends on these environments.

Light pollution affects the hormonal cycles of marine life

Light pollution has a detrimental impact on the hydrosphere, affecting marine life from whales to fish, coral, and plankton. A significant consequence of light pollution is its disruption of the hormonal cycles of marine organisms, which can have far-reaching effects on their behaviour and reproduction.

Marine life has evolved over millions of years to align with natural light intensity and patterns, including the glow of moonlight and starlight. However, with the increasing presence of artificial light from human development along coasts, the natural light cues that marine organisms rely on are being washed out. This disruption to their natural light environment has been shown to impact their hormonal cycles, which in turn affects their behaviour and reproductive strategies.

One illustrative example is the case of sea turtles. Artificial light negatively impacts female sea turtles seeking secluded, dark locations to lay their eggs. The presence of artificial light discourages them from coming ashore, which can ultimately lead to a decrease in reproduction rates. Additionally, hatchlings that would naturally orient themselves towards moonlight on the water are instead drawn towards inland lights, leading to dehydration and starvation.

The issue of light pollution is exacerbated by the growing use of LED lighting, which often emits more short-wavelength light than traditional lighting and can penetrate deeper into the water. This change in the nature of artificial light further confounds the ability of marine organisms to interpret their environment and maintain their natural hormonal cycles.

To mitigate the impact of light pollution on the hydrosphere, experts suggest several strategies. These include the use of red light, which does not penetrate as far into the water, and the erection of barriers to shield coastlines from artificial light. Additionally, there is a critical need for more comprehensive data collection and research on a broader geographic scale to fully understand the extent and specific consequences of light pollution on various marine organisms and ecosystems.

Artificial light disrupts the feeding, schooling and migration of fish

Artificial light has a significant impact on the behaviour and physiology of fish. It disrupts their internal clocks, affecting their growth, development, and spawning migration. This, in turn, has consequences for their feeding, schooling, and migration patterns.

Fish exhibit a behaviour known as phototaxis, an instinctive movement towards or away from light. This behaviour influences their navigation, hunting, and reproductive patterns. Artificial light can alter these patterns, causing erratic feeding and predatory behaviours. For example, bass begin food hunting at dawn and dusk, benefiting from lowered visibility. Artificial light can disrupt this natural cycle, making their feeding patterns more unpredictable.

The use of artificial light in fishing is a controversial technique. While it increases efficiency and productivity by attracting fish to the light source, it also disrupts the ecological balance by attracting non-target species and increasing by-catch mortality. This can have negative consequences for fish populations and the environment.

Additionally, artificial light can affect the schooling behaviour of fish. Baitfish, for instance, group together under the cover of light sources at night to confuse potential predators and increase their chances of survival. Artificial light can interfere with this defensive strategy, making them more vulnerable to predators.

Furthermore, artificial light can impact the migration patterns of fish. The spawning migration of diadromous (migratory) fish, for example, can be disrupted by artificial light. This can affect the reproductive physiology of these fish, potentially influencing the continued existence of the species.

In conclusion, artificial light has far-reaching effects on the behaviour and physiology of fish. It disrupts their internal clocks, growth, development, and reproductive patterns, which in turn can affect their feeding, schooling, and migration. This has implications for both the fish populations and the balance of aquatic ecosystems.

Noise pollution interferes with the communication of marine animals

Noise pollution in the ocean has increased dramatically over the last few decades. This is extremely damaging to marine wildlife, as most marine species are highly dependent on sound for their survival. Visibility is often low underwater, so sound is an important sensory signal for marine animals, especially for marine mammals such as whales, dolphins, and porpoises. They rely on sound to communicate, locate mates and prey, avoid predators, navigate, and defend their territories.

For example, increased ship noise has caused bottlenose dolphins to simplify their vocal calls. Higher dolphin whistle frequencies and a reduction in whistle complexity have been recorded, and this simplification may reduce the information content of their calls, thereby decreasing effective communication. Marine mammals may compensate for noise by making their signals longer, increasing the volume of their calls, shifting their sound frequency, or waiting to signal until the noise has passed. However, these changes can be costly.

Noise pollution can also cause stress in animals, increase the risk of mortality by unbalancing predator-prey interactions, and interfere with sound-based orientation, especially in reproductive contexts. It can further lead to auditory masking, which is when the perception of one sound is affected by the presence of another sound, and physiological damage to the hearing system, including cochlear damage and hair cell loss.

To reduce noise pollution in the marine environment, policies are needed to reduce propeller noise from ships and mitigate the sounds of sonar equipment, seismic air guns, pile driving, and construction. Quieter technologies must also be developed. These actions can improve the ocean soundscape and potentially enable the recovery of some marine life.

Ocean noise reduces the ability of animals to hear environmental cues

Ocean noise pollution is a form of environmental pollution caused by human activities that generate unnatural and excessive sound underwater. This includes commercial shipping, oil exploration, seismic surveys, offshore wind turbine installation, military sonar, recreational boating, and energy exploration. These activities can interfere with the ability of marine animals to hear and interpret natural sounds in the ocean, including environmental cues that are vital for survival.

Marine mammals, such as whales, dolphins, and porpoises, are highly dependent on sound for their survival. They rely on sound to communicate, locate mates and prey, navigate, and defend their territories. Ocean noise pollution can obscure and disrupt these natural behaviours, making it harder for them to survive. For example, noise can cause whales and dolphins to alter their migration routes, leading them into dangerous situations, such as encountering predators or getting trapped in sea ice.

Noise pollution can also affect the ability of marine animals to hear important environmental cues, such as cues related to finding food, navigating to preferred habitats, and avoiding predators. For instance, zooplankton, which are sensitive to light intensities, move vertically in the water column during the day to avoid surface predators. Light pollution from artificial lighting can disrupt this behaviour, causing a decrease in the number of individuals migrating and the amplitude of vertical migration, which can lead to a proliferation of microalgae on the water surface. This, in turn, can impact the balance of aquatic ecosystems, including prey-predator relationships and food chains.

Additionally, ocean noise pollution can cause hearing loss in marine animals, further impairing their ability to interpret environmental cues. Very loud sounds can cause panic and disorientation, leading to abnormal behaviour such as ascending too quickly to escape the noise, which can result in decompression sickness and tissue damage from gas bubble lesions. In some cases, loud sounds have been linked to mass stranding events, with the number of recorded strandings likely representing only a small percentage of what is actually happening, as severely injured animals rarely make it to shore.

Light pollution negatively impacts the reproduction of marine life

Light pollution has a detrimental impact on the reproduction of marine life, affecting everything from whales and fish to coral and plankton.

Impacts on Sea Turtles

One of the most well-known examples of the effects of light pollution on marine life is the disruption it causes to sea turtles. Artificial light negatively impacts sea turtles in two significant ways. Firstly, female sea turtles seeking a dark and quiet spot to lay their eggs may be deterred by bright lights and may ultimately decide not to come ashore. Secondly, hatchling sea turtles, which naturally move towards the moonlight reflecting on the water, are drawn towards inland lights instead, leading to dehydration or starvation.

Impacts on Coral Reef Ecosystems

Coral reef ecosystems, which are vital for the maintenance of coral reefs, are also affected by light pollution. Studies have shown that exposure to artificial light can cause oxidative stress and photosynthetic impairment in coral, impacting their metabolism and reproduction. The timing and synchronization of coral spawning, which is crucial for the maintenance of coral reefs, can be disrupted by light pollution, leading to asynchronous reproduction and potential reproductive isolation.

Impacts on Zooplankton and Food Chains

Zooplankton, which play a crucial role in marine food chains, exhibit daily vertical migration. During the day, they move to deeper waters to avoid surface predators and feed on phytoplankton at night. However, light pollution disrupts this natural cycle by keeping the environment illuminated at night. This disruption can lead to a decrease in zooplankton migration and a proliferation of microalgae on the water surface, potentially impacting prey-predator relationships and water quality.

Impacts on a Broader Scale

The effects of light pollution on marine life are not limited to specific species but can also have broader ecological consequences. The widespread use of LED lighting exacerbates the problem as LEDs produce light with shorter wavelengths that penetrate deeper into the water. This can affect the vision and behaviour of various marine organisms, including whales and fish, that have evolved to adapt to natural light intensity and patterns.

Mitigation Strategies

To mitigate the negative impacts of light pollution on marine life, it is recommended to use as much red light as possible, as it does not penetrate as far into the water. Implementing "Lights Out" campaigns, which aim to darken skies to help migrating birds drawn to artificial light, will also benefit marine systems near coastal cities. Additionally, physical barriers can be erected to shield coastlines from artificial light.

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