Effects of Underwater Noise Pollution on Marine Mammals

This is a portion of a power point presentation given by Dr. Marsha Green in June 2004 that addresses the impact of high intensity sonar, airguns and shipping on the marine environment. It also addresses International actions being taken concerning this issue.

1. Whales are acoustic animals – They use sound to:

  • Navigate
  • Find mates
  • Find food
  • Communicate

2. Research shows that whales avoid sounds with a source level of about 120 dB (Richardson et al., 1995, Green et al., 1998)
There are sound sources in the ocean that produce noise levels much higher than 120 dB:

  • Air guns used for oil exploration & geophysical research (216 – 230 dB)
  • Underwater construction
  • Explosives
  • Military sonars
  • Large ships
  • Acoustic harassment devices

3. These very loud underwater sounds may cause various adverse effects on marine mammals including:

  • Masking social communications used to find mates or identify predators
  • Temporary and permanent hearing loss or impairment
  • Displacement from preferred habitat
  • Disruption of feeding, breeding, nursing and communication
  • Strandings
  • Death and serious injury from hemorrhaging and tissue trauma

4. Public and scientific concern about underwater noise pollution has grown over the last decade after a series of mass mortalities of cetaceans associated with the use of mid-frequency active sonar in coastal areas.

The best documented cases, where stranded animals were recovered in time for necropsy occurred in:

  • Bahamas (2000)
  • Madeira (2000)
  • Canary Islands (2002)
  • Bahamas 2000
  • Canary Islands 2002

5. Cuvier’s and other beaked whale species suffered hemorrhaging in:

  • Brain
  • Inner ear
  • Lungs
  • Eyes
  • Consistent with injury from intense sound (Fernandez et al 2003 & Jepson et al 2003)

6. Other strandings correlated with the use of naval sonar occurred in:

  • Greece (1996)
  • US Virgin Islands (1998,1999)
  • Canary Islands (1985, 1986, 1989)
  • NW Coast of US (2003)

However, the magnitude of the problem is not known since recent evidence indicates whales may die at sea where carcasses sink and are almost impossible to detect.

7. Are Current “Safe” Exposure Levels Really Safe?

  • It now appears that at least some of the injured whales in the Bahamas stranding were exposed to sound levels of 160-165 dB
  • In their Environmental Impact Statement the Navy extrapolated that the safe exposure level for marine mammals is 180 dB

8. High intensity sonar has been shown to have adverse impacts on other marine species as well.

9. The British Defense Research Agency reports that fish exposed to Low Frequency Active Sonar above 160 dB suffered:

  • Internal injuries
  • Eye hemorrhaging
  • Auditory damage
  • Fifty-seven percent of brown trout died after exposure to levels above 170 dB.

10. Air Guns:

  • Air guns (216 – 230 dB) can also cause marine mammal strandings and affect fish
  • Used to find and monitor oil reserves
  • Often operate for long periods of time
  • Fire every few seconds
  • Norway’s Institute of Marine Research found that trawl catch rates of haddock and cod fell 45 – 70% over a 5,000 square kilometer area when air guns were being used.
  • Catch rates did not increase for the five days surveyed after air guns stopped.
  • Many species show active avoidance at 3-20 km
  • Blue whales stopped vocalizing for 1 hour at 10 km distance
  • Sperm whales stopped vocalizing for 36 hours at 370 km distance
  • Sperm whale distribution has been observed to change in response to seismic operations in the Gulf of Mexico
  • Two beaked whales stranded in the Gulf of California in September 2002, one hour after a research vessel using air guns was 22 km away
  • Whales stranded in the Galapagos Islands while the same research vessel was operating in the area (2000)

11. Shipping:

  • The main source of noise is the ship’s propeller which produces a loud hiss that dominates the low frequencies below 600 Hz in heavy shipping areas
  • The leading noise producers are oil tankers and bulk dry ships
  • Icebreakers cause avoidance reactions in narwhales, belugas, walruses
  • Some whales rely on low-frequency sound for communication over vast distances
  • These are the same frequencies occupied by vessel noise
  • Some scientists are concerned that shipping could have population – level impacts on these species
  • One scientist reported that 1/3 of all stranded cetaceans they necropsied had some form of auditory damage

12. International Actions on Ocean Noise Pollution:

  • International institutions have begun to recognize that noise is a form of pollution.
  • The 1982 UN Convention on the Law of the Sea (UNCLOS) defines pollution of the marine environment as “the introduction by man� of substances or energy into the marine environment which results in�such deleterious effects as harm to living resources and marine life.”
  • The Scientific Committee of the International Whaling Commission addressed the issue of noise in 1998, 1999 and 2000.
  • The International Maritime Organization has stated that noise from ship traffic is a hazard to the marine environment.
  • The Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas (ASCOBANS) has recognized the dangers of underwater noise pollution in its Conservation Management Plan.
  • The Scientific Committee to the Agreement on the Conservation of Cetaceans of the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS) issued a formal recommendation on Man-Made Noise in 2003.

13. Petitions:

  • Signed by 70 conservation and animal welfare organizations
  • Representing over 8 million people in North America and Europe
  • Have been submitted to NATO and the Parliament of the European Union
  • Calling for the development of a Multinational Task Force to develop international standards to regulate underwater noise
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