Underwater noise emissions

Context

According to a recent study, continuous shipping activity has been identified as a key factor in the rise in ocean noise levels worldwide.

Probable Question

Underwater noise emissions pose a serious threat to marine life. Comment (150 words, 10 marks)

Key Findings of Recent Studies

Underwater sound pressure levels

• The UNE, or underwater sound pressure levels, in the Indian waters, are 102-115 decibels, relative to one microPascal (dB re 1µ Pa).
• The East Coast level is slightly higher than that of the West. 
• There is an increase by a significant value of about 20 dB re 1µPa.

Factors contributing Underwater Noise Emissions

• Continuous shipping movement is identified as a major contributor to the increase in the global ocean noise level.
• The frequencies of ships’ underwater self-noise and machinery vibration levels overlap the marine species’ communication frequencies in the low-frequency range of less than 500 Hz." "This is called masking.

Impact of Underwater Noise Emission

• The rising man-made (anthropogenic) underwater noise emissions (UNE) from ships in Indian waters pose a threat to the lives of marine mammals like Bottlenose Dolphin, Manatees, Pilot Whales, Seals, and Sperm Whales.
• The sound that radiates from ships on a long-term basis affects them and results in internal injuries, loss of hearing ability, changes in behavioral responses, masking, and stress. There are Acute and Chronic noise categories in the emissions.
• Masking could have led to a change in the migration route of the marine species to the shallow regions and also made it difficult for them to go back to the deeper water.

About the underwater ambient noise levels

• The measurement of the ambient noise levels was carried out by deploying a hydrophone autonomous system around 30 nautical miles from the Goa coastline. 
• The depth of deployment of the sensor was 11 meters in a water depth of 22 meters. 
• The single-channel hydrophone was deployed at different locations with an in-water depth of 18 meters with a deployment depth of 3 and 5 meters off Visakhapatnam port.

About Underwater Noise Pollution

• Sound is a highly efficient means of communication underwater and is the primary way that many marine species gather and understand information about their environment. 
• Many aquatic animals use sound to find prey, locate mates and offspring, avoid predators, guide their navigation, and locate habitat, as well as to listen and communicate with each other.
• Underwater noise pollution refers to sounds made by human activities that can interfere with or obscure the ability of marine animals to hear natural sounds in the ocean.

Reasons for Ocean Noise

• Over the last century, human activities such as shipping, recreational boating, and energy exploration have increased along our coasts, offshore, and in deep ocean environments. 
• Noise from these activities can travel long distances underwater, leading to increases and changes in ocean noise levels in many coastal and offshore habitats.

Impact of Ocean Noise

• These rising noise levels can negatively impact ocean animals and ecosystems. 
• Higher noise levels can reduce the ability of animals to communicate with potential mates, other group members, their offspring, or feeding partners. 
• Noise can also reduce an ocean animal's ability to hear environmental cues that are vital for survival, including those key to avoiding predators, finding food, and navigating to preferred habitats.

Initiative to Curb Ocean Noise Pollution

• Slow-down initiative: One of the simplest ways to reduce ocean noise is to simply ask ships and boats to slow down when passing through areas with a lot of marine life. 
• Retrofitting ships: Retrofitting ships is typically more expensive than changing the designs and components of new ships, but if just the most problematic ships are targeted, it might be worthwhile. Moreover, it would lessen ocean noise. 

News Source: The Hindu

https://www.thehindu.com/sci-tech/energy-and-environment/underwater-noise-emissions-by-ships-pose-threat-to-marine-species-says-study/article66524789.ece

https://oceanservice.noaa.gov/facts/ocean-noise.html

Frequently Asked Questions about Underwater noise emissions

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