Avoiding Ocean Noise Pollution: Strategies For Marine Conservation

Marine life is under threat from a new kind of pollution: noise. Caused by human activities such as commercial shipping, oil exploration, seismic surveys, offshore wind turbine installation, and military sonar, ocean noise pollution is a growing problem.

Noise travels faster and further in water than in air, and with upwards of 250,000 vessels travelling across the global ocean at any one time, the background noise in the ocean has increased significantly. This is particularly harmful to marine mammals like whales and dolphins, who rely on echolocation and vocalisations to communicate, navigate, hunt, and reproduce.

Noise pollution can cause hearing loss, stress, changes in behaviour, and even death. It can also lead to decompression sickness as animals ascend too quickly to escape the noise, causing gas bubble lesions and, in some cases, fatal tissue damage.

While there are currently no international standards for the regulation of ocean noise pollution, there are ways to reduce it. Slowing ships down by 10% could reduce ocean noise pollution by 40%, and some organisations are campaigning for this to be implemented. Quieter technologies can also be used, and some ports are offering incentives for vessels that comply with environmental guidelines.

Reduce vessel speed

Slowing down vessels is an effective way to reduce noise pollution in the ocean. This is because the noise emitted by vessels is directly related to their speed. In other words, the faster a vessel goes, the louder the noise it produces.

Reducing vessel speed is an effective noise mitigation measure, especially over deep water. Slowing down vessels can reduce underwater noise by up to 67% and this effect is most stable in deep areas where vessels are evenly distributed rather than restricted to single shipping lanes.

In shallow-water environments, the stability of noise reduction is more difficult to achieve because traffic is often restricted to shipping lanes. However, rerouting shipping traffic in these areas can help to avoid exposing sensitive regions to noise.

By reducing vessel speed, the area exposed to ship noise is markedly decreased. This leads to a reduction in the number of animals affected by underwater noise. Additionally, slower vessels take longer to pass an animal, which reduces the overall exposure time during which an animal may be affected by noise.

Reducing vessel speed also has positive effects beyond noise reduction. It can lower the risk of ships colliding with whales and reduce greenhouse gas emissions from shipping.

One challenge of reducing vessel speed is the possible need for more ships to maintain the same cargo throughput. However, this can be offset by the fact that slower ships call into port less often.

Another challenge is that slower vessels may be less effective at reducing noise levels in shallow waters, as the attenuation of sound with distance is more complex in these environments.

Implement quieting technology on ships

Implementing quieting technology on ships is one of the most effective ways to reduce noise pollution in the ocean. Here are some ways this can be achieved:

• Reducing cavitation: Cavitation is the formation and rapid collapse of bubbles produced by a rotating propeller, and it is the main source of underwater sound produced by ships. By minimising cavitation through better maintenance and optimising the propeller design, underwater noise can be significantly reduced.
• High-skew propeller blades: Propellers with a "high skew" can reduce the vibration of a vessel's body and propeller noise.
• Hull and propeller design: The shape of a ship's hull and the resulting wake affect propeller performance and noise production. By designing hulls and propellers together, a more uniform wake can be achieved, reducing noise.
• Low-noise machinery: Selecting equipment with inherently low noise and vibration levels is crucial. Machinery that is directly bolted to the hull usually produces the highest levels of underwater sound, so using vibration isolators and/or isolation mounts can help reduce noise transmission.
• Reducing ship speed: Slowing down vessels not only reduces underwater noise but also lowers the risk of whales being rammed by ships. It also reduces fuel consumption and emissions of greenhouse gases and air pollutants.
• Regular maintenance: Regular propeller cleaning and maintenance of a smooth underwater hull surface can help reduce surface roughness, cavitation, and resistance, leading to lower noise production and increased energy efficiency.

These methods of implementing quieting technology on ships are essential to mitigate the harmful effects of ocean noise pollution on marine life.

End seismic surveys for oil and gas

Seismic surveys are used to locate and estimate the size of offshore oil and gas reserves. To do this, ships tow multiple air gun arrays that emit thousands of high-decibel explosive impulses to map the seafloor. The sound produced by these air guns can be heard at great distances, and the noise levels in some ocean regions have doubled every decade since the 1950s.

The auditory assault from seismic surveys has been found to damage or kill fish eggs and larvae and to impair the hearing and health of fish and marine mammals, making them vulnerable to predators and leaving them unable to locate prey or mates or communicate with each other. These disturbances can disrupt and displace important migratory patterns, pushing marine life away from suitable habitats like nurseries and foraging, mating, spawning, and migratory corridors. This is especially dangerous for critically endangered species like the North Atlantic right whale, of which there are only 411 individuals left in the world, where just one death can have population-wide impacts. In addition, seismic surveys have been implicated in whale beaching and stranding incidents.

Seismic air guns are among the loudest sources of noise in the ocean, emitting highly intense noise blasts of up to 260 decibels every 10 to 15 seconds. The sound travels through the water and into the seabed, bouncing off various layers of rock, oil or gas. The faint echoes are then picked up by sensors towed by the same vessel. During surveys, the air guns are fired every 10-15 seconds to develop a detailed geological picture of the ocean floor in the area.

The impact of seismic surveys on marine life is becoming an increasingly prevalent consideration for the offshore oil and gas industry. There is no off-the-shelf treatment to reduce underwater sound, but there are several approaches that could be taken to reduce unwanted sound during seismic exploration. One approach is to limit the output of seismic signals to the useful frequency range, as many sea animals have hearing that is focused primarily in the higher frequency range. Another approach is to use Marine Vibroseis, an "underwater speaker" that creates sound only in the useful frequency range below 100 Hz. The potential for sound reduction is large, particularly at higher frequencies.

To avoid noise pollution in the ocean, it is necessary to end seismic surveys for oil and gas.

Transition to renewable energy sources

Transitioning to renewable energy sources is a crucial step in reducing ocean noise pollution. Here are some ways this can be achieved:

Wave Energy Converters

Wave energy converters harness the power of surface waves to generate electricity. One type of converter uses wave motion as a piston to drive air in and out of a chamber, with the moving air driving a turbine. This technology is particularly useful for powering offshore activities and isolated island and coastal communities. While wave energy converters are generally costlier than other renewable energy technologies, they have the potential to reduce carbon emissions and provide power to regions that may not have access to reliable electricity sources.

Tidal Energy Converters

Tidal energy converters generate electricity from the movement of tidal currents, similar to how wind turbines work. These converters are often submerged turbines that spin from the current's propeller. Tidal energy is more predictable and stable than other renewable sources, making it ideal for supporting and stabilizing electrical grids. This technology could also aid in disaster recovery by providing affected communities with a resilient energy source.

Ocean Thermal Energy Converters (OTEC)

OTEC power plants convert thermal differences between warm surface seawater and cold deep seawater into electricity. Warm surface water is pumped through an evaporator, producing vapour that drives a turbine generator. This technology is intended for large-scale power plants and could be used to stabilize electrical grids that integrate other renewable sources like solar and wind. However, OTEC currently has limited deployments due to the uncertainty of return on investment.

Tidal Kites

Tidal kites are an innovative technology that can harness both high-velocity tidal currents and lower velocity offshore currents. They are "kites" tethered underwater that use control flaps to move in a fixed pattern across the current, increasing the speed of water flow across the turbine blades to extract more energy. This technology could be used to capture energy from tidal currents for commercial deployments.

Benefits of Transitioning to Renewable Energy Sources

Transitioning to renewable energy sources offers a multitude of benefits. Firstly, it helps reduce greenhouse gas emissions and mitigate climate change. Secondly, it provides a healthier environment by reducing air pollution and improving air quality. Additionally, renewable energy creates more jobs than the fossil fuel industry and promotes inclusive economic growth and poverty alleviation. It also makes economic sense, as the reduction of pollution and climate impacts can lead to significant cost savings. Finally, renewable energy sources are readily available in most countries, reducing the dependency on fossil fuel imports and protecting countries from unpredictable price swings.

Avoid overlapping shipping traffic with high densities of marine life

Shipping routes in the ocean are akin to roads on land, in that they are regularly used thoroughfares that concentrate the movement of vessels between multiple locations. These "marine roads" have a significant impact on marine giants such as great whales, basking sharks, and whale sharks, who are vulnerable due to their need to surface frequently to breathe, their large body size, and long-range ocean movements. To address this issue, we propose the following strategies to avoid overlapping shipping traffic with areas of high marine life density:

Strategies to Avoid Overlapping Shipping Traffic:

• Relocate shipping lanes: By relocating shipping lanes away from areas of high marine life density, we can reduce the risk of collisions and other negative impacts on marine species. This strategy has been successfully implemented in some regions, such as the relocation of shipping lanes away from areas with high whale densities.
• Implement Traffic Separation Schemes: Traffic Separation Schemes involve establishing designated lanes or routes for vessels to follow, similar to road lanes for vehicles. This helps to separate shipping traffic from areas with high marine life density, reducing the risk of collisions and other disturbances.
• Establish Dynamic Management Areas: These areas are designed to minimize whale mortality by taking into account the interannual distribution of whale species. By establishing Dynamic Management Areas, vessel traffic can be redirected away from areas with high whale densities, reducing the risk of ship strikes.
• Reduce vessel speed: Slowing down vessels can significantly reduce the risk of collisions with marine life. This strategy not only reduces the risk of ship strikes but also decreases underwater noise pollution, which can interfere with the communication and behavior of marine species.
• Use alternative fuels and technologies: Transitioning to cleaner fuels and adopting quieter ship designs can help reduce underwater noise pollution, which is a significant issue for marine life.
• Improve monitoring and data collection: By investing in better monitoring technologies and data collection methods, we can gain a deeper understanding of marine life distribution and shipping traffic patterns. This information can then be used to inform more effective management strategies.
• Expand and enforce marine protected areas: Establishing and strictly enforcing marine protected areas can provide safe havens for marine life, free from the disturbances of shipping traffic. This includes areas where whale densities are high, as well as critical habitats such as feeding and breeding grounds.
• Promote international cooperation and regulations: Collaboration between nations and the implementation of international regulations are crucial to address this global issue. Organizations like the International Maritime Organization (IMO) play a vital role in establishing guidelines and standards to reduce the impact of shipping on marine life.

By implementing these strategies and working together globally, we can effectively avoid overlapping shipping traffic with areas of high marine life density, contributing to the conservation and protection of our ocean's precious biodiversity.

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