Central idea: The rising man-made (anthropogenic) underwater noise emissions (UNE) from ships in the Indian waters are posing a threat to the life of marine mammals like Bottlenose Dolphin, Manatees, Pilot Whale, Seal, and Sperm Whale.

What is Underwater Noise Emissions (UNE)?

• Underwater noise emissions (UNE) refer to sounds that are produced underwater as a result of various human activities such as shipping, oil and gas exploration, military sonar, and construction.
• UNE can have a significant impact on marine life, as many marine animals rely on sound for communication, navigation, and foraging.
• Excessive underwater noise can interfere with these activities, and can even cause physical harm to marine animals in some cases.
• As a result, there is growing concerned about the potential impact of UNE on marine ecosystems, and efforts are being made to better understand and mitigate these impacts.

UNE and marine life

• Impacts behavioural aspects: The main form of energy for multiple behavioural activities of marine mammals, which include mating, communal interaction, feeding, cluster cohesion and foraging, is based on sound.
• Threats posed by UNE: The sound that radiates from ships on a long-term basis affects them and results in internal injuries, loss of hearing ability, change in behavioural responses, masking, and stress.

Key findings about Indian waters

• Continuous shipping movement is identified to be a major contributor to the increase in the global ocean noise level.
• 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, where there is an increase by a significant value of about 20 dB re 1µPa.
• “The frequencies of ships’ underwater self-noise and machinery vibration levels are overlapping the marine species’ communication frequencies in the low-frequency range of less than 500 Hz.
• This is called masking, which could have led to a change in the migration route of the marine species to the shallow regions and also making it difficult for them to go back to the deeper water.

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