The U.S. Navy has been working to advance its ability to detect enemy submarines for decades. The Navy’s low-frequency sonar system has been a topic of controversy among environmental advocates for years. This system, known as Surveillance Towed Array Sensor System Low Frequency Active (SURTASS LAF) allows the Navy to detect enemy submarines with enough time to react and defend themselves. During the course of developing and testing the SURTASS LFA system, environmental interest groups raised concerns that the system may cause harm to marine mammals. Whales use sound for communication, navigation, orientation, and in locating food. This is known as echolocation. The Navy’s mid-frequency sonar can cause whales to dive deeper into the ocean, or rise quickly. Like humans, whales can get the bends from these types of underwater movements. The loud noises created by the Navy’s sonar system are believed to interrupt their ability to communicate, navigate and look for food. These disruptions are believed to harm the whales physically and cause state of panic which often leads to strandings and collisions (Drumm).
Active sonar utilizes sound in order to find objects in the water. A pulse is sent through the water, and then reflects off an object. This is called an echo. The receiver will convert the echoes into electrical signals which are digitally displayed on board the vessel. The high tech computers will be able to extract information such as distance and direction of the object. A major draw back of active sonar is that once a pulse is sent out, enemy vessels can track were it came from. In order to manage the risk of being detected, active sonar is used only for short periods. Different types of active sonar operate at different frequencies, according to their purpose. There are three types of active sonar: high frequency, mid frequency and low frequency. High frequency sonar is typically used to identify the depth of water. Mid frequency sonar has been employed since World War II. It is mainly used to detect submarines. The purpose of low frequency sonar is long range search and surveillance of submarines. The opposite of active sonar is passive sonar (Bellis).
Passive sonar use underwater microphones called hydrophones. These listening devices are able to receive, amplify, and process under water sounds. The sonar operator will compare the sounds to known frequencies of enemy submarine engines. The disadvantage of passive sonar that it is difficult to track ultra quiet submarine engines, which why active sonar is used. Unlike active sonar, passive sonar uses no sound in the water which does not reveal a friendly presence to the enemy (Whales and Sonar).
The Navy has spent over $16 million in conducting research to determine the impact its devices will have on the environment. Part of this extensive research process included the development of an Environmental Impact Statement (EIS). In an effort to reduce the risk the SURTASS LFA system poses to marine mammals, the Navy has undertaken numerous measures to restrict the operation of the system. These procedures include careful visual and acoustic monitoring of marine wildlife while the system is being employed and stringent geographic limitations on where it can be used (SURTASS LFA). In addition to the resources spent developing the Environmental Impact Statement, the Navy commits almost $10 million a year for research to help understand how sonar and other sounds affect whales and other marine mammals. At the present time, the use of active sonar is the most effective way for the Navy to defend against enemy submarines (Whales and Sonar).
In March of 2005, 80 dolphins were stranded off the coast of Florida. Of those stranded, 29 died. This occurred on the same day a submarine mission employing sonar was conducted. While it can be speculated that this situation was linked to the mission, it is also know that dolphins and whale strandings in Florida are not uncommon. They can occur due to illness within the pod or other natural causes (Babson).
A federal investigation concluded that the use of sonar was likely the cause of the 2000 stranding of 16 whales off the coast of the Bahamas. This stranding is the only one that the Navy has admitted to being linked to the use of its sonar system. Following the investigation it was stated that the use of tactical mid-range frequency sonar was the most likely cause for the incident. Of those stranded, ten were pushed back to sea and six died. Upon examination of those that did not survive, it was found that all of the whales suffered hemorrhaging near their ears. While this would not have been fatal had they been pushed back to see, it may have caused the whales to come to shore again due to disorientation (USA Today).
In October of 2005, the Navy was sued by the Natural Resources Defense Council (NRDC) and other environmentalist groups. The NRDC and other groups claimed that the active sonar being used by the Navy was disturbing, and in some cases killing whales and dolphins. The evidence is based on the deaths of at least 37 whales in January of 2005 off the coast of North Carolina. Prior to these deaths, the Navy had conducted mid-frequency sonar training. The plaintiffs requested that the Navy discontinue use of mid-frequency sonar when used for training purposes and to avoid highly populated areas. Mid-frequency sonar is the most used method currently employed for detecting enemy submarines (CNN). According to a spokesperson the Navy, some of the demanded measures are already in place to protect marine mammals.
Perhaps the most recent news regarding this ongoing battle is the Navy’s proposed plans to build an underwater warfare training range in the Atlantic Ocean. If the plans are approved, the new training station will be off the coast of North Carolina, Virginia or Florida. To add to the angst, the area in North Carolina being considered is the same area where the 37 whales were beached this past January (National Geographic).
Even with all the research conducted by the Navy, it is hard to believe that all the incidents near sonar testing sites are merely coincidental. This will continue to be a topic of controversy for years to come. At some point the Navy will admit to more of these occurrences being related to the testing. However, by that time many more marine mammals will have died and some of which are already endangered. We have a seemingly limitless ability to develop new technologies. Given this, one would think that we would develop a tool that the Navy could use to do its job and not risk harming marine mammals. Although, the Navy states that it is striving to avoid further disturbing marine mammals, they will only go so far before compromising national security becomes and issue. While it is important to be aware of the impact this testing has had on marine mammals, concerned environmentalists need to think about where we might be someday if the Navy was not able to prepare to defend our country.

Works Cited
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Babson, Jennifer “Dolphins stranded on day of sub mission.” Miami Herald. 12 November 2005.
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Bellis, Mary. “The History of Sonar.” About.com. 12 November 2005.
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Drumm, Laura. “Cetacea Echolocation.” 3 March 2004. National Marine Mammal Laboratory.
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Mott, Maryann. “Whales at Risk From New U.S. Navy Sonar Range, Activists Say.” 3
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“Navy sued for sonar blasting whales.” 20 October 2005. CNN. 12 November 2005.
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