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Home > Environmental Issues > Article >

Underwater noise:
Death knell of our oceans?

Linda Weilgart, Ph.D
Assistant Professor of Biology, Dalhousie University
7 November 2005

Most marine animals, particularly marine mammals and fish, are dependent on sound, sometimes for all aspects of their life including reproduction, feeding, predator avoidance, and navigation (Popper 2003).

Marine life has used sound as its principal sense because sound travels so efficiently underwater, travelling 5 times the speed of sound in air. Vision is only useful for tens of meters underwater, yet sound can be heard for hundreds, even thousands of kilometers.

Unfortunately, the same goes for noise, or unwanted sound. For instance, the U.S. Navy's Low Frequency Active (LFA) Sonar used to detect submarines could affect marine life over an area of about 3.9 million (Johnson 2003), an area covering much of the Pacific Ocean. (LFA sonar can be heard over an even larger area, but this figure is based on noise levels shown to actually affect whales and fish).

Noise from just a single seismic survey can flood through a region of almost 300,000, raising noise levels 100 times higher, continuously for days at a time (IWC 2004).

Loud air guns with a sound level of 200 to 250 decibels are used for seismic surveys by the oil and gas industry to find oil up to 10km underneath the ocean floor.

Seismic noise from eastern Canada measured 3,000 km away in the middle of the Atlantic was the loudest part of the background noise heard underwater (Nieukirk et al. 2004).

Ocean background noise levels have doubled every decade for the last six decades in some areas, mainly due to shipping (IWC 2004).

Such noise can prevent fish, whales, and dolphins from hearing their prey or predators, from avoiding dangers, from navigating or orienting to important habitat, from finding mates that are often widely spread out, or from staying in acoustic contact with their young or their group members.

Whale calls seem to be becoming increasingly drowned out by our noise (Nieukirk et al. 2004).

What kinds of impacts from noise on marine life have been found?

Recently, noise has been shown to be deadly for at least some species of whales. The evidence linking intense military sonars with fatal whale strandings is undeniable (e.g. Frantzis 1998; Jepson et al. 2003).

The International Whaling Commission's Scientific Committee noted "there is now compelling evidence implicating military sonar as a direct impact on beaked whales in particular" (IWC 2004).

Even a U.S. Navy-commissioned report stated that "the evidence of sonar causation [of whale beachings] is, in our opinion, completely convincing." (Levine et al. 2004)

Often whales show bleeding around their brain, in their ears, in other structures to do with hearing, and in other organs of their body (e.g. NOAA and U.S. Navy 2001; Fernandez et al. 2005).

Mass strandings of certain types of whale increased dramatically after 1961 when more powerful naval sonars began to be used (Friedman 1989).

Seismic air guns have been thought to cause whale strandings as well (Taylor et al. 2004; Engel et al. 2004).

Even giant squid have apparently mass stranded because of air guns, suffering massive internal injuries and badly damaged ears (MacKenzie 2004).

Many sub-lethal effects have also been documented. These may be as serious as lethal effects, because they may affect more animals yet be harder to detect. Seismic air guns have been shown to severely damage fish ears, most likely permanently, at distances of from 500m to several kilometers from seismic surveys (McCauley et al. 2003).

Reduced catch rates of 50-80% and fewer fish near seismic surveys have been reported in species such as cod, haddock, rockfish, herring, and blue whiting (Engas et al. 1996; Dalen and Knutsen 1987; Lokkeborg 1991; Slotte et al. 2004; Skalski et al. 1992).

These effects can last up to five days after exposure and at distances of more than 30 km from a seismic survey. Increases in stress hormones (Santulli et al. 1999) and strong behavioral reactions have been observed in fish due to noise. Day-to-night movements of fish were changed near air guns (Wardle et al. 2001).

Fish also showed reactions like dropping to deeper depths, becoming motionless, becoming more active, or forming a compact school (Dalen and Knutsen 1987; McCauley et al. 2000; Pearson et al. 1992; Santulli et al. 1999; Skalski et al. 1992; Slotte et al. 2004).

Snow crabs under seismic noise conditions showed bruised organs, abnormal ovaries along with bleeding, stress, delayed embryo development, and smaller larvae (DFO 2004).


Andre, M, Kamminga, C., and Ketten, D. 1997. Are low-frequency sounds a marine hazard: a case study in the Canary Islands. Underwater Bio-sonar and Bioacoustics Symposium, Loughborough University.

Balcomb, K.C. and Claridge. D.E. 2001. A mass stranding of cetaceans caused by naval sonar in the Bahamas. Bahamas J. of Science 8(2): 1-12.

Bryant, P.J., C.M. Lafferty, and S.K. Lafferty. 1984. Reoccupation of Laguna Guerrero Negro Baja California, Mexico, by gray whales. Pp. 375-386 in M.L. Jones, S.L. Swartz, and S. Leatherwood (eds.). The Gray Whale Eschrictius robustus. Academic Press, Orlando, Florida. 600 pp.

Dalebout, M. L, Robertson, K. M., Frantzis, A., Engelhaupt, D., Mignucci-Giannoni, A., RosarioDelestre, R. J., and Baker, C. Scott. In Press. Worldwide structure of mtDNA diversity among CuvierÕs beaked whales (Ziphius cavirostris): implications for threatened populations. Molecular Ecology.

Dalen, J. and Knutsen, G. M. 1987. Scaring effects on fish and harmful effects on eggs, larvae and fry by offshore seismic explorations. Pp. 93-102. In: Merklinger, H. M. (Ed.). Progress in Underwater acoustics. New York: Plenum Press.

Department of Fisheries and Oceans (DFO). 2004. Potential impacts of seismic energy on snow crab. DFO Can. Sci. Advis. Sec. Habitat Status Report 2004/003.

Engel, M. H., Marcondes, M. C. C., Martins, C. C. A., Luna, F. O., Lima, R. P., and Campos, A. 2004. Are seismic surveys responsible for cetacean strandings? An unusual mortality of adult humpback whales in Abrolhos Bank, northeastern coast of Brazil. Paper SC/56/E28 presented to IWC Scientific Committee, Sorrento, Italy (unpublished). [Available from the Office of the Journal of Cetacean Research and Management.]

Engas, A. Lokkeborg, S., Ona, E., and Soldal, A.V. 1996. Effects of seismic shooting on local abundance and catch rates of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus). Can. J. Aquat. Sci. 53: 2238-2249.

Fernandez, A., Edwards, J. F., Rodriguez, F., Espinosa de los Monteros, A., Herraez, P., Castro, P., Jaber, J. R., Martin, V., and Arbelo, M. 2005. "Gas and fat embolic syndrome" involving a mass stranding of beaked whales (Family Ziphiidae) exposed to anthropogenic sonar signals. Vet Pathol 42:446Š457.

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392: 29.

Friedman, N. 1989.The Naval Institute Guide to World Naval Weapons Systems. Annapolis, MD: Naval Institute Press, pp. 380-382.

International Whaling Commission Scientific Committee (IWC/SC). 2004. Annex K: Report of the Standing Working Group on Environmental Concerns. Annual IWC meeting, Sorrento, Italy, 29 June - 10 July 2004. 56 pp.

Johnson, J. S. 2003. SURTASS LFA environmental compliance experience. Presentation at ECOUS (Environmental Consequences of Underwater Sound), May 12-16, San Antonio, Texas.

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Whales have moved away from their feeding and mating grounds (Bryant et al. 1984; Morton and Symonds 2002; Weller et al. 2002), moved away from their migration route (Richardson et al. 1995), and have changed their calls due to noise (Miller et al. 2000).

They have blundered into fishing nets (Todd et al. 1996) or were unable to avoid ships (Andre et al. 1997) most likely due to hearing damage as a result of noise.

Indications of increased stress and a weakened immune system following noise broadcasts were also shown for a whale and dolphin (Romano et al. 2004).

Are these impacts serious?

Certainly deaths of individuals are serious, particularly in endangered species. But impacts on populations, even non-lethal ones, can severely affect species survival.

The International Whaling Commission's Scientific Committee noted "... repeated and persistent acoustic insults [over] a large area ... should be considered enough to cause population level impacts." (IWC 2004).

Population impacts are hard to detect in animals as difficult to study as marine mammals, but noise has been thought to contribute to several whale species' decline or lack of recovery (NMFS 2002; Weller et al. 2002).

Anything that interferes with a marine animal's ability to detect biologically important sounds could have a negative effect on its survival and the health of its populations. Reef fish larvae, for instance, use sound to orient toward or select suitable habitat (Simpson et al. 2005).

Certain whale species, such as beaked whales, could be highly threatened by noise not only because of their apparent sensitivity, but also because they seem to occur in small isolated populations that stay in the same area all year (Dalebout et al., in press), making them more vulnerable to local extinctions.

Indeed, the best population data we have from the Bahamas 2000 stranding indicates that almost the entire local population either moved away permanently or were killed by a single military sonar event (Balcomb and Claridge 2001).

It is possible, even probable, that other local beaked whale populations have disappeared without our knowing it, since these are the most shy and difficult to study of all whales.

The impacts of noise can work cumulatively or synergistically with other environmental threats. For instance, human impacts on marine ecosystems such as over-fishing, eutrophication, climate change, and ultraviolet radiation interact to produce a magnified effect (Worm et al. 2002; Lotze and Worm 2002).

Noise could interact with marine mammal by-catch or ship collisions, preventing animals from sensing fishing gear or oncoming ships.

It is impossible to know what the effects of noise are on the entire marine ecosystem, but from what we know now, the consequences could be far-ranging and severe.

Noise has killed and deafened marine animals, caused them to move away from important breeding and feeding areas, and produced declines in fisheries' catch rates.

Ocean noise is getting dramatically louder every decade. It is time to start listening.

The Maui dolphin Cephalorhynchus hectori maui is endemic to the west coast of the North Island of New Zealand. It is critically endangered with no more than 100 remaining. Dead dolphins have washed ashore after being entangled in fishing nets, which may have happened after being disoriented by ocean noise.

Jepson, P. D., Arbelo, M., Deaville, R., Patterson, I. A. P., Castro, P., Baker, J. R., Degollada, E., Ross, H. M., Herraez, P., Pocknell, A. M., Rodriguez, F., Howie, F. E., Espinosa, A., Reid, R. J., Jaber, J. R., Martin, V., Cunningham, A. A., and Fernandez, A. 2003. Gas-bubble lesions in stranded cetaceans. Nature 425: 575-576.

Levine, H., Bildsten, L, Brenner, M., Callan, C., Flattˇ, S., Goodman, J., Gregg, M., Katz, J., Munk, W., Weinberger, P. 2004. Active Sonar Waveform. JSR-03-200. Report from MITRE Corporation, JASON program, for the Office of Naval Research.

Lækkeborg, S. 1991. Effects of a geophysical survey on catching success in longline fishing. ICES (CM) B:40.

Lotze, H. K. and Worm, B. 2002. Complex interactions of climatic and ecological controls on macroalgal recruitment. Limnol. Oceanogr. 47: 1734-1741.

MacKenzie, D. 2004. Seismic surveys may kill giant squid. New news service, 22 Sept. New Scientist
See article

McCauley, R.D., Fewtrell, J, Duncan, A. J., Jenner, C., Jenner, M.-N., Penrose, J.D., Prince, R. I. T., Adhitya, A., Murdoch, J., and McCabe, K. 2000. Marine seismic surveys: analysis and propagation of air-gun signals; and effects of air-gun exposure on humpback whales, sea turtles, fishes and squid. CMST 163, Report R99-15, prepared for the Australian Petroleum Production Exploration Association from the Centre for Marine Science and Technology, Curtin University, Perth, Western Australia.

McCauley, R.D., Fewtrell, J., and Popper, A.N. 2003. High intensity anthropogenic sound damages fish ears. J. Acoust. Soc. Am. 113 (1): 638-642.

Miller, P.J.O., N. Biasson, A. Samuels, and P.L. Tyack. 2000. Whale songs lengthen in response to sonar. Nature 405: 903.

Morton, A.B. and H.K. Symonds. 2002. Displacement of Orcinus orca (L.) by high amplitude sound in British Columbia. ICES J. Marine Science 59: 71-80.

National Marine Fisheries Service (NMFS). 2002. Status Review under the Endangered Species Act: Southern Resident Killer Whales (Orcinus orca). National Oceanic and Atmospheric Administration Technical Memorandum NMFS NWAFSC-54, Seattle, WA. 131 pp.

Nieukirk, S. L., Stafford, K. M., Mellinger, D. K., Dziak, R. P., and Fox, C. G. 2004. Low-frequency whale and seismic airgun sounds recorded in the mid-Atlantic Ocean. J. Acoust. Soc. Am. 115(4): 1832-1843.

NOAA and U. S. Navy. 2001. Joint Interim Report; Bahamas Marine Mammal Stranding Event of 15-16 March 2000. National Oceanic and Atmospheric Administration.
See article

Photo credit:
Above top: Humpback whale tail, Helen McConnell, Crown Copyright © Department of Conservation

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