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Tuesday, Oct 22, 2019

World Oceans Day: Noise in Indian seas will double every 10 years, affect marine life

Study says noise levels from ship movement to blame for marine and animal deaths, government needs to bring in rules to better situation

mumbai Updated: Jul 06, 2018 17:13 IST
Badri Chatterjee
Badri Chatterjee
Hindustan Times
The study states that decibel levels in the seas have increased from a maximum of 185-190dB to 210dB over seven decades.
The study states that decibel levels in the seas have increased from a maximum of 185-190dB to 210dB over seven decades.(HT File Photo)

Ship movement in the Arabian Sea, Bay of Bengal and Indian Ocean will cause noise levels to double every 10 years, affecting marine life, according to a study by Maritime Research Centre (MRC), Pune, under the Indian Maritime Foundation that was released a day before the World Oceans Day (June 8).

The study, Acoustic Habitat Degradation Due to Shipping in the Indian Ocean Region (IOR), states decibel (dB) levels in the seas have increased from a maximum of 185-190dB to 210dB over seven decades. In this period, the minimum noise levels along major shipping routes, too, have gone up to 110dB from 90-95dB. The increasing noise could have an adverse impact on marine life, adding that the rise in cases of whales and other marine mammals dying along the coast could be attributed to shipping.

Sources of noise
  • > 200dB: Sound from ships for communication purposes or to detect any danger
  • 200-250dB: Seismic surveys air guns are used to illuminate the sea bottom to understand the nature and detect presence of oil activity
  • 100-150dB: Sounds of various machines that aide movement of large ships and vessels

According to the United Nations Conference on Trade and Development (UNCTAD), the Indian Ocean, Arabian Sea and Bay of Bengal represent 20% of the world’s ocean area. Apart from Navy ships and vessels deployed for security purposes, seaborne trade, including regular export-import goods, dry cargo, petroleum products, gas load, and crude oil, has increased from 5,000 million tonnes (mt) in 1970 to 20,000 mt in 2014 (UNCTAD). More recent data from the Indian National Shipowners’ Association shows the trade increased to 27,500 mt by 2017.

Noise from ships causes discomfort to marine mammals, in some cases leading to internal injuries, bleeding and haemorrhages, or even death, said researchers. As part of the study, MRC carried out spatiotemporal mapping of the sound exposure level (SEL) for whales in the low frequency band of 20 hertz (Hz) to 3 kilohertz (kHz). “Movement of ships propagates noise below 1 kHz. Marine mammals have different frequency bands for multiple functions such as navigation, communication, foraging, finding mates for breeding, and avoiding predators. For instance, the Blue whale uses 300Hz to communicate, while dolphins and porpoises use around 150 kHz. When the sound of the ships matches the frequency of their communication signals, it affects them internally,” said Arnab Das, author of the study, former commander in the Indian Navy and director of the Maritime Research Centre.

According to the Maharashtra Maritime Board (MMB), almost 30,000 large ships and vessels are identified every year along the entire Indian coastline, excluding smaller domestic ships (over 400) and lakhs of fishing boats. The study found that the seas off the west coast of the country were noisier owing of heavier density of ship traffic. “Around 65% of the ships are located along the west coast. Neither the environment ministry nor any global body has set a safe limit for noise levels in the sea,” said an official from MMB.

There are several examples in the recent past where excessive noise from fishing has led to marine animals losing their sense of direction, said experts. “The situation can get better only if the union environment ministry intervenes,” said E Vivekanandan, consultant and scientist, Central Marine Fisheries Research Institute, Chennai.

“Marine traffic noise has risen with increasing demand and rise in global commodities trade. India does not have complete control over the Indian Ocean Region. The involved countries and stakeholders need to take a joint decision. However, as a part of the National Wildlife Action Plan 2017-2031 (released in October 2017), the union environment ministry has come up with a list of guidelines to protect aquatic, coastal and marine ecosystems. Noise affecting these species is also one of the aspects covered,” said a senior official from the Ministry of Environment, Forests and Climate Change (MoEFCC).

Conscious efforts could salvage the situation, claim experts. “The government needs to take efforts to protect marine species, as with more demand, this shipping activity will only increase and further threaten this marine habitat,” said Das.


Dead dolphin washed ashore at Versova beach.
Dead dolphin washed ashore at Versova beach.

A day before the World Oceans Day (June 8), decomposed carcass of a 7-ft Indo-Pacific humpback dolphin washed ashore at Versova beach on early Thursday morning. This is the fourth marine mammal death at a city beach this year, and 84th such case in Mumbai over the past three years.

A forest guard from the state mangrove cell spotted the carcass. “The dolphin was so badly mutilated that a post-mortem was not possible. We buried the dolphin at the beach,” said Prashant Deshmukh, range forest officer (west), state mangrove cell.

First Published: Jun 08, 2018 12:21 IST

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