Underwater noise emissions.

• Underwater noise emissions by ships pose threat to Indian marine species, as per a study.
• The noise results in injuries and changes in their behavioural response besides a shift in their migration route much to their loss.
• The measurement of the ambient noise levels was carried out by deploying a hydrophone autonomous system around 30 nautical miles from the Goa coastline.

Highlights of the Study

• Increased UNE Levels:The sound pressure levels of UNE in the Indian waters are 102-115 decibels, relative to one microPascal (dB re 1µ Pa). (Scientists have agreed to use 1µPa as the reference pressure for underwater sound).
• 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: major source is continuous shipping movement.

Impact:

• 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 may lead 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.
• However, 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.
  • UNE is posing a threat to the life of mammals like Bottlenose Dolphin, Manatees, Pilot Whale, Seal, and Sperm Whale.
  • 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.

About Marine Sound Pollution

• Marine sound pollution is the excessive or harmful sound into the ocean environment. It is caused by a variety of human activities, such as shipping, military sonar, oil and gas exploration, and recreational activities like boating and jet skiing.
• It can have many negative impacts on marine life.