Anthropogenic Noise Pollution and Cetaceans

Brittany Bartlett, RJD Intern

It is no secret that our oceans and the species within them face a wide range of anthropogenic, human induced threats. And, as a result, the health of the ocean is rapidly declining. Among these threats is that of pollution; plastics, oil, runoff, etc. One form of pollution that tends to be overlooked is noise pollution, specifically the use of Navy Sonar.

Navy sonar is used as a security measure to detect underwater objects. It emits pulses of sound into the water, which then proceed to bounce of objects beneath the ocean and create echoes. These echoes are then received and information of the specific object is transmitted (Los Angeles Times 2008). Although an important device for security and defense purposes (as it is used to detect foreign enemies beneath the water), navy sonar releases a noise which exceeds 230 decibels. This sound, which is equivalent to multiple jet engines (Drake 2011), negatively impacts marine life. Therefore, the use of navy sonar in our oceans is a heavily debated and highly controversial issue.

A humpback whale. Fritz Geller-Grimm, Wikimedia Commons

A humpback whale. Fritz Geller-Grimm, Wikimedia Commons

In the last 25 years there has been an estimated 25% increase in cetacean strandings (UK Cetacean Stranding Investigation Programme). It is also important to remember that this statistic most likely undershoots reality. The percentage, 25% excludes the concept of ‘hidden mortality’ in which many more species are killed unknown to us (Parsons et al 2008). Research has proved that one reason for this increase is the result of loud noises beneath the water, such as navy sonar, which have both behavioral and physiological effects on cetaceans.

Through acoustic masking, loud noises have the capacity to affect and interfere with the daily activity of cetaceans. For one, feeding behavior via the concept of “avoidance behavior” has been known to occur; species will avoid areas where navy sonar is apparent, despite the fact that it is a prevalent feeding ground (Zirbel et al 2011). Researchers and observers have also noticed significant modifications to the vocalizations of various cetacean species. In the presence of navy sonar, Sperm whales became silent, finned pilot whales increased their vocalizations, and Humpback whales’ song lengths increased. These abnormal activities have the capacity to interfere with breeding and overall social interaction (Zirbel et al 2011).

On a more severe level, navy sonar has the potential to cause life threatening physiological damage, such as hemorrhaging and embolisms within key organs (Fernandez et al 2005; Crum et al 2005). These events have been found in multiple navy sonar stranding cases. It is, therefore, believed that navy sonar has the capacity to a) create nitrogen bubbles within organs or b) alter diving behavior and cause decompression sickness to occur (Crum et al 2005). Although research is uncertain of which hypothesis is accurate, navy sonar has been linked to the development of hemorrhaging and fat emboli within cetaceans on more than once occasion.

To date, the legal battle to prevent the use of navy sonar has not been unsuccessful (Zirbel et al 2011) as a result of uncertainty, lenient legislation, and a lack of public awareness.      Although research has provided evidence that noise pollution causes the above physiological and behavioral issues, uncertainty always remains within science, inhibiting the likelihood of action. For example, in one case, Ocean Mammal Institute (a marine mammal date collecting organization), motioned for an injunction against the Navy for not following the National Environmental Policy Act, Marine Mammal Protection, or the Endangered Species Act. However, the court sided with the navy due to the fact that no adequate proof of irreparable harm existed (Zirbel et al 2011).

The use of navy sonar raises political discrepancy and a security vs. environmental conflict. Since the events of September 11th, the U.S has been in a state of heightened security. Therefore, policy tends to prioritize defense and security and thus, the use of sonar. As a result, environmental legislation tends to be lenient (Zirbel et al 2011).

Unfortunately, action is hindered by a lack of public awareness and concern. Many individuals surveyed were unaware that noise pollution effected cetaceans. If this persists, the government will have no motivation or incentive to assess the situation and, therefore, the issue of noise pollution will not become high on the political agenda.

So, what can be done to tackle the issue of navy sonar? To begin, the precautionary principle must guide all action (Parsons et al 2008); cautious action must be taken to limit harm if uncertainty exists. With this principle in place, further research must be performed to convince the public of the negative effects of sonar on all marine animals (Andre 2011). Passive Acoustic Monitoring (PAM) and Listening to the Deep Ocean Environment (LIDO) are two techniques which provide spatial and temporal data on marine and marine mammal noise (Andre 2011).

Do you believe navy sonar impacts marine mammals (zirbel et al 2011)

Do you believe navy sonar impacts marine mammals (zirbel et al 2011)

Following this, policy must be restructured. Not only must current policy be strengthened to minimize the gaps, but marine protected areas must be emplaced in necessary areas (i.e. breeding and feeding grounds) to reduce the effects of sonar on marine animals (Gannier 2010). Policy must also allow for better communication and heightened public awareness. The U.S government will only take action if encouraged and influenced by American civilians. Therefore, it is in our hands to reduce the effects of noise pollution and help to save our oceans.



Andre, M., et al. “Listening to the Deep: Live Monitoring of Ocean Noise and Cetacean Acoustic            Signals.” Marine pollution bulletin 63.1-4 (2011): 18-26.

Crum, LA, et al. “Monitoring Bubble Growth in Supersaturated Blood and Tissue Ex Vivo and    the Relevance to Marine Mammal Bio effects.” Acoustics Research Letters Online-Arlo         6.3 (2005): 214-20.

Drake, Nadia. “Scientists study sonar’s impact on whale behavior.” Santa Cruz Sentinel [Santa      Cruz] 13 12 2010, n. pag. Web. 26 Nov. 2011.\.

Fernandez, A., et al. “”Gas and Fat Embolic Syndrome” Involving a Mass Stranding of Beaked    Whales            (Family Ziphiidae) Exposed to Anthropogenic Sonar Signals.” Veterinary    pathology 42.4 (2005): 446-57.

Gannier, A. “Using Existing Data and Focused Surveys to Highlight Cuvier’s Beaked Whales       Favourable Areas: A Case Study in the Central Tyrrhenian Sea.” Marine pollution        bulletin 63.1-4 (2010): 10        17.

Parsons E.C.M, et al. “Navy sonar and cetaceans: Just how much does the gun need to smoke      before we act?” Marine Pollution Bulletin 56.7 (2008): 1248-1257.

“Whale and dolphin strandings ‘increase by 25%.” BBC News. UK Cetacean Stranding  Investigation Programme 2010.          11829112.


Zirbel, K., P. Balint, and E. C. M. Parsons. “Public Awareness and Attitudes Towards Naval         Sonar   Mitigation for Cetacean Conservation: A Preliminary Case Study in Fairfax      County, Virginia (the  DC Metro Area).” Marine pollution bulletin 63.1-4 (2011): 49-55.


Zirbel, K., P. Balint, and E. C. Parsons. “Navy Sonar, Cetaceans and the US Supreme Court: A     Review of Cetacean Mitigation and Litigation in the US.” Marine pollution bulletin 63.1         4 (2011): 40-8.


Image References:


Fritz Geller-Grimm. Wikimedia Commons. 2002.


Zirbel, K., P. Balint, and E. C. M. Parsons. “Public Awareness and Attitudes Towards Naval         Sonar Mitigation for Cetacean Conservation: A Preliminary Case Study in Fairfax      County, Virginia (the DC Metro Area).” Marine pollution bulletin 63.1-4 (2011): 49-55.

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