How sonar kills whales: new theory
From ANIMAL PEOPLE, April 2001:
Washington, D.C.; FRIDAY HARBOR, Washington–Five years of rising controversy over U.S. Navy deployment of low-frequency active sonar moved toward head-on collision when Center for Whale Research founder Ken Balcomb on February 23 published details of his contention that LFA kills whales with harmonic resonance that destroys their inner ears, while on March 19 the National Marine Fisheries Service served notice in the Federal Register that it is almost ready to give the Navy a five-year Incidental Take permit which would allow full deployment to proceed.
The Federal Register notice opened a 45-day public comment period, to close on May 3, on a proposed rule to govern “Taking Marine Mammals Incidental to Navy Operations of Surveillance Towed Array Sensor System Low Frequency Active Sonar,” called SURTASS-LFA for short.
The Federal Register notice explained that the U.S. Navy wants “a small take exemption under section 101(a)(5)(A) of the Marine Mammal Protection Act, for the taking of marine mammals incidental to operation of the SURTASS-LFA sonar for a period of time not to exceed five years…There would be a maximum of four SURTASS-LFA sonar systems with a nominal maximum of two systems at sea at any one time.
“The purpose of SURTASS-LFA sonar is to provide the Navy with a reliable and dependable system for long-range detection of quieter, harder-to-find submarines,” the often highly technical notice continued. “Low-frequency sound travels in seawater more effectively and for greater distances,” than the high-frequency sound used by most other sonar.
“The SURTASS-LFA sonar system would meet the Navy’s need for improved detection and tracking of new-generation submarines at a longer range,” NMFS said. The idea behind it would be to detect and intercept enemy submarines before they could get close enough to the U.S. to launch nuclear weapons.
“Because of the offshore nature of SURTASS-LFA sonar operations,” NMFS said, “the Navy does not believe that there is a potential for SURTASS-LFA sonar to result in marine mammal stranding incidents.”
But NMFS said that “the Navy plans to coordinate with worldwide marine mammal stranding networks and report any correlations between SURTASS-LFA and strandings.”
Strandings, indicated Balcomb, are relevant to how SURTASS-LFA harms whales only as a source of physical evidence confirming killings which he believes may occur wherever the sonar system is used. Most of the remains of whales killed by SURTASS-LFA, Balcomb believes, will not drift ashore.
Details of the SURTASS-LFA system have leaked out to the marine mammal protection community in bits and pieces for more than 10 years. The scraps of information began to rouse opposition in mid-1996.
“Between August 1988 and July 1994, the U.S. Navy conducted 22 LFA field exercises,” Natural Resources Defense Council attorney Joel Reynolds disclosed via MARMAM, an electronic bulletin for marine mamologists, in September 1996. “The Navy states that they were conducted ‘without known adverse impact on marine mammals.’ Other exercises have been conducted since then,” Reynolds continued, citing times and places. The Navy has concluded that no ‘takes’ by harassment or otherwise would occur from operation of LFA. Therefore no permits have been obtained either under the Marine Mammal Protection Act or the Endangered Species Act. Any comments?”
As previously unexplained observations of apparent relevance to the various LFA tests surfaced from all over the world, opposition to SURTASS-LFA developed. Freedom of Information Act requests have confirmed that by mid-1997 government agencies were already receiving warnings from their senior scientists that SURTASS-LFA might be a disaster-in-the-making for whales, though no one could quite explain why the whales were harmed.
Responding to the accumulating evidence, NMFS began requiring the Navy to seek incidental take permits for further tests.
Lawsuits and public protest greeted the Navy when tests were held off Hawaii in early 1998, and have dogged SURTASS-LFA ever since–especially after NMFS-commissioned whale acoustics expert Darlene Ketten reported in June 2000 that Navy anti-submarine sonar tests off the northern Bahamas on March 15, 2000 may have caused 16 whales of four different species to beach themselves on the islands of Abaco, Grand Bahamas, and North Eleuthera during the next 48 hours.
Seven of the whales died, including four Cuvier beaked whales and a Blainville’s dense beaked whale, all of whom are considered extremely rare.
“I’m not ready to say the Navy did it,” Ketten said, but added that “The coincidence of the timing and the pattern of the stranding with the presence of Navy sonars raises a red flag.”
After the strandings, the Navy suspended sonar tests which had been scheduled for May 2000 off the New Jersey coast.
Most of the remains of whales allegedly killed by the Bahamian testing decomposed too soon to provide definitive answers, but the Center for Whale Research, begun at Friday Harbor, Washington, in 1976, now has a Bahamian headquarters as well, and founder Ken Balcomb was present when several stranded beaked whales came up nearby. Balcomb saw fresh blood in their eyes, inner ears, lungs, and brain tissue.
Sea Shepherd Conservation Society founder Paul Watson amplified attention to the strandings from aboard the Ocean Warrior, which was already in the vicinity en route to campaign against whaling in the Faroe Islands of the North Atlantic.
Bodies of evidence
Balcomb had already stated opposition to SURTASS-LFA in comments sent to NMFS during November 1999. He took almost a year to study the Bahamian strandings before formally commenting again. His February 23 statement came as an open letter to SURTASS-LFA environmental impact surveillance program manager Joseph S. Johnson, amplified via posting to MARMAM.
The Bahamian strandings, Balcolm said, “unequivocally demonstrated the lethality of high-powered sonars, and provided the opportunity to understand how sonar has been inadvertently killing whales in vast expanses of ocean around the world,” as had been suspected without anyone being able to verifiably explain the cause-and-effect links.
“The killing is largely due to resonance phenomena in the whales’ cranial airspaces that are tearing apart delicate tissues around the brains and ears,” Balcolm argued. “This is an entirely separate issue from [the alleged] auditory thresholds and traumas that the Navy has fixated upon. In my earlier comments,” Balcolm said, “I questioned whether there might be a problem with injurious resonance, but now I have seen the problem and can attest to the fact that there is massive injury to whales caused by sonar.”
In other words, Balcolm contends now that the sound volume generated by SURTASS-LSA is not the problem, contrary to most previous discussion, which has always been confounded by awareness that many other oceanic activities–both natural and human-created–put out more loud sound.
Instead, according to Balcolm, the threat to whales results from the regular, repetitive emission of sounds at a particular frequency and volume which rarely occurs in nature, and to which whales seem to be extremely sensitive–perhaps in part because some species use modulated low-frequency sound for communication.
The problem might be compared to what happens when an opera singer uses her voice to shatter a crystal glass, although it occurs in the opposite sound range.
“Resonance,” Balcolm explained, “can contribute to shear forces that can be quite damaging–wings tear off airplanes,” as occurred to several experimental aircraft in the early days of jet-powered flight, “bridges gallop,” like the Tacoma Narrows Bridge which fell in 1938, “and buildings collapse,” as in some long-tremoring but otherwise mild earthquakes, “due to unanticipated resonance phenomena which can afterward be explained by simple physics and mechanics.
“The scientific and medical literature contains numerous examples,” Balcolm continued, “of hemorrhagic injuries and death occurring in humans when they are inadvertently exposed to loud sound, particularly at their lung airspace resonance frequency. Undoubtedly such damage could also be demonstrated as occurring to whales, if they could be tested and did not sink to the bottom of the ocean when they die.
In the whales stranded after SURTASS-LFA testing in the Bahamas, however, “It is the volume of air in the individual pterygoid sacs and the laryngeal airspace, not the lungs, for which resonance should be calculated,” Balcolm said.
“Below about 100 meters,” Balcolm explained, “virtually all of the air that was in the whales’ lungs at the surface is forced into laryngeal and cranial airspaces. It has a total volume less than that of a football. The two largest of the remaining airspaces are bilaterally adjacent to the earbones and the base of the brain. Their diminishing volume at depth is compensated for by retia mirabilia, a vascular network extending to the middle ear.
“Envision the football-sized airspace further squeezed to the size of a ping-pong ball,” Balcolm offered, “with 1,500 pounds per square inch of air pressure [50 times the pressure that keeps a car tire rolling], now tucked between the ear bulla and the skull on each side of the head, thinly separated from a bag of blood next to it on the soft side.
“The frequencies of LFA, and other powerful mid-frequency sonars, match the cranial airspace resonance frequencies in these whales at the depths where they normally forage,” Balcolm asserted.
“Now envision rapidly compressing and decompressing the ping-pong ball many times per second, until ultimately the amplitude is exaggerated by resonance. The result is both astonishing and bloody. Many whales died due to this sonar resonance,” both in the Bahamas and in earlier LFA testing off Greece, Balcolm said. “Unfortunately, the Greek incident passed into relative obscurity,” because investigators “missed the crucial point of matching resonance in critical airspaces, and because suitable specimens were not collected for discovering the problem.”
Balcolm necropsied four of the whales who came ashore in the Bahamas.
“All of them evidenced hemorrhage in the acoustic regions of the cranium and mandible and in tissues adjacent to airspaces around the earbones,” Balcolm reported.
“One fresh specimen evidenced a brain hemorrhage with a direct path to the ear hemorrhage. This same specimen [also] evidenced lung hemorrhage and laryngeal hemorrhage upon dissection. These hemorrhages are of the type reported in laboratory animals exposed to LFA at lung resonance frequency, and they strongly corroborate the theoretical explanation of such injuries in these whales.
“I have been told,” Balcolm added, “that the Bahamian situation may have been complicated by oceanographic conditions and other factors that could have resulted in a surface sound duct in which most of the acoustic energy was trapped; but I also documented that the whales stranded over an area 200 kilometers across!
“The Navy cannot reasonably mitigate the problem using visual, active acoustic, or passive acoustic monitoring,” Balcolm concluded, “nor can the Navy redesign the whales. At best, it can only reconsider and perhaps redesign the SURTASS-LFA system.”
Receiving Balcolm’s comments, SURTASS-LFA environmental impact study chief Joseph A. Johnson told Bremerton Sun reporter Christopher Dunagan that he did not see how resonance could be the problem that Balcolm says it is.
Claimed Johnson, “The frequency changes and sound levels used in LFA are not great enough to cause injury in whales, although they may cause behavioral changes,” and opined that LFA cannot be harming whales because blue whales and humpbacks emit sounds at similar volume and frequency.
“The Navy can throw up all kinds of theoretical reasons why it didn’t happen,” responded Balcolm, who was a Navy pilot for eight years before beginning his whale studies in 1976. “But it happened. There has to be something wrong with the theory. I’m trying to get them to look.”