Friday 9 March 2012

How Navy Sonar Kills Whales and Dolphins

The following excerpts were taken from a letter written by the Biodiversity Legal Foundation, which does an excellent job of explaining how sound kills whales and other forms of marine life:
“Sound penetrates an animal’s body when immersed in water. Essentially all of acoustic energy goes into a body immersed in water. This effect, which can cause tissue rupture and hemorrhage, has not been adequately addressed in the Navy’s [environmental impact statement]. The implications (of the effect of sound penetration) for marine life are very serious, as described next.”
“The first lethal mechanism involves moderate level sound waves activating the growth of microscopic bubbles in the supersaturated blood and tissue of cetaceans. These bubbles then grow and can cause embolisms, hemorrhaging and localized pressure on the nervous system. Significant oxygen deprivation by blood vessel blockage can kill brain cells and produce stroke. For supersaturated gasses dissolved in cells rather than the blood, activation of bubble formation can rupture the cell walls.”
“The second mechanism for lethal injury involves hemorrhaging caused by acoustic resonance of the LFA [Low Frequency Active] sonar signal in cranial and other airspaces such as lungs and swim bladders. Specifically, the rapid change in pressure (from very high to very low several times per second for the duration of the one-minute LFA sonar blast) can rupture the delicate membranes enclosing the airspace.”
“Animals with air filled lungs and swim bladders are especially vulnerable because of the large difference in impedance between air in the lungs or swim bladders and their body tissues or seawater. Submerged animals exposed to explosions at short range showed hemorrhage in the lungs and ulceration of the gastro-intestinal tract.”
“The killing is largely due to resonance phenomena in the whales’ cranial airspaces that are tearing apart delicate tissues around the brains and ears.”
The Navy is accepting public comments on this sonar program until April 27th, 2012, voice your opinion here. You can copy and paste this or write your own comment: “In addition to its impacts on marine mammals and endangered species, I believe that the Navy and NMFS have a responsibility to consider the full extent of the “collateral damage” that will occur with deployment of LFA sonar, and that you must consider the cumulative effects on all forms of marine life that will be adversely affected over areas totaling thousands of square miles. Therefore, the testing and use of this must cease immediately.”
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