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The US Navy's Low Frequency Active Sonar:
Cause for Concern
Marsha L. Green, Ph.D.
Ocean Mammal Institute

Low frequency active sonar (LFA sonar) is a dangerous technology that has the potential to kill, deafen and/or disorient whales, dolphins and all marine life, as well as humans, in the water. It is the loudest sound ever put into the world's oceans. The U.S. Navy was planning to deploy it in 80% of the world's oceans at a level of 240 decibels in order to detect quiet submarines. Some other countries have similar technology. In 1996 LFA sonar during NATO exercises in the Mediterranean was correlated with a stranding of beaked whales.

Background Information on the Impact of Underwater Noise on Marine Mammals and Fish

There is a significant body of research showing that whales avoid underwater sounds starting at 110-120 dB re 1 Pa. (In this paper all decibel levels refer to a reference pressure level of 1 Pa). Several studies (Malme et al., 1983, 1984, 1986, 1988) show that grey whales begin to avoid sounds at exposure levels of 110 dB and more than 80% of the whales showed avoidance to sounds of 130 dB. Ninety percent of the whales avoided airgun pulses at 180 dB. Typically whales slowed down and moved around the sound source. At times they moved into the shallow surf zone to avoid the noise, respiration rates increased and there were indications that mother-calf pairs were more sensitive to the noise than other whales.

Bowhead whales react to a received level of 115 dB and Ljungblad et al., (1988) noted behavioral changes in bowhead whales more than 8 km away from seismic vessels with received noise levels of 142 - 157 dB. Bowles et al., (1994) reported that sperm whales stopped vocalizing in response to a seismic vessel hundreds of kilometers away.

In a report submitted to National Marine Fisheries Service in March, 1998 on the impact of engine noise on the Hawaiian humpback whale, researchers at the Ocean Mammal Institute found that whales swim 2 to 3 times faster away from engines of 120 dB than they do around quieter engines. Research by the Ocean Mammal Institute also shows that the presence of a boat up to mile away significantly changes the behavior of humpback whales.

While cetaceans show avoidance behavior to sounds starting around 115 dB, more intense sounds can cause physiological damage. Noise also can mask biologically important signals such as vocalizations by other animals. Richardson et al., (1991) suggest that if baleen whales show low auditory thresholds for low frequency sounds, then sound levels of 195-210 dB might result in immediate damage to their auditory organs. Lien et al., (1993) studied reactions of humpback whales in response to explosions and drilling off Newfoundland. Their data revealed only small changes in residency, movements and general behavior. However, two humpback whales trapped in fishing gear after the explosions were found to have severely damaged ear structures similar to blast injury in humans. Lien et al. noted that the whales showed no dramatic behavioral reaction to these harmful sounds and cautioned that whales' visible short-term reactions to loud sounds may not be a valid measure of the degree of impact of the sound on them.

In their chapter "Underwater Noise Pollution and its Significance for Whales and Dolphins", (In Simmonds and Hutchinson, 1996), Jonathan Gordon and Anna Moscrop state that shock waves caused by intense underwater sound sources can cause direct tissue damage. Animals with air filled lungs and swim bladders are especially vulnerable because of the large difference in impedance between air in the lungs and their body tissues or sea water. Submerged animals exposed to explosions at short range showed hemorrhage in the lungs and ulceration of the gastro-intestinal tract.

Sound also can have a deleterious biological effect by initiating the growth of stabilized microbubbles that are known to exist in mammalian tissue. Gas bubbles larger than a few tens of microns can block capillaries which can lead to pathological conditions. Crum and Mao (1996) calculated the growth rates of bubbles exposed to low frequency acoustic fields. Their results indicate that for sound pressure levels in excess of 210 dB (re 1m Pa) significant bubble growth can be expected to occur, and divers and marine mammals exposed to these conditions could be at risk.

Loud underwater sounds also, of course, affect fish and other marine life. Studies show harmful effects of even moderate noise on hearing in fish and the viability of fish eggs exposed to noisy environments was significantly reduced (Myrberg, 1990). On March 10, 1998 the "Seattle Times" reported that hundreds of dead fish appeared in Lake Washington after 240 dB airgun blasts were used to test for earthquake faults. Seismometers dozens of miles away picked up the air gun pulses and nearby residents felt their beds shaking.

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Documented Effects of Sonar on Whales and Humans

After WWII the Norwegians used sonar to hunt whales because they found the sonar frightened especially baleen whales and caused a predictable flight response making them easier to catch. (Mitchell et al., 1981) Sperm whales became silent, stopped their activities and scattered in response to military sonar signals (Watkins et al., 1985) and humpback whales showed avoidance when sonar was played back to them (Maybaum, 1989).

In 1991 Simmonds and Lopez-Jurado in Nature noted the association between three strandings of whales (including two pygmy sperm whales, a bottle-nosed whale and eighteen beaked whales) in the Canary Islands in 1985, 1988 and 1989 and the times at which naval fleets had been visibly operating in the area close to stranding sites. Local people were aware of such naval maneuvers only three times since 1985 and on each occasion mass live strandings occurred. In a more recent statement in Nature (March 5, 1998), Alexandros Frantzis linked a stranding of Cuvier's beaked whales in the Mediterranean to military low frequency active (LFA) sonar trials the day before. Cuvier's beaked whales rarely strand. A Bioacoustics Panel investigated this stranding and it is clear that the NATO vessel transmitting the LFA sonar came within 10 km of the beach where the whales stranded. The panel concluded these whales were exposed to LFA sonar at 150-160 dB. The US Navy's proposed LFA sonar will produce a sound field of 150-160 dB up to at least 100 miles away from the transmitting vessel, putting large numbers of whales, dolphins and other marine life at risk. As recently as July and early August, 1998 a beaked whale and a sperm whale stranded on Kauai while the Navy was engaged in maneuvers in Hawaii (RIMPAC '98). There is evidence that a stranding of beaked whales in the Caribbean in October 1999 was due to sonar as people in the water heard the loud sounds and got out of the water.

From 1980 to 1995 the Navy developed and tested LFA sonar without obeying any of the applicable environmental laws. While the Navy was illegally developing and testing LFA sonar, they were also building a ship (TAGOS-23, estimated cost $60 million) to deploy the sonar. The Navy finally agreed to prepare an Environmental Impact Statement (EIS) after being challenged by environmental groups. They hired Christopher Clark (Cornell U.) and Peter Tyack (Woods Hole Oceanographic Institute) to test the effects of the sonar on blue, fin, gray and humpback whales in 1997 and 1998. It is important to note that the LFA sonar test levels were always much lower than the actual sonar which is about 240 dB.

On August 25, 1994 a scuba diver was accidentally exposed to testing of the US Navy's LFA sonar system. (Comments submitted at Public Hearing of California Coastal Commission, 12/12/97). The ship transmitting the sonar was over 100 miles northwest of the diver who reported distinct and disorienting lung vibration as a result. Pestorius and Curley (1996) exposed Navy divers to low frequency active sonar and reported that one of the divers had to be hospitalized and was later under treatment for seizures. A Hawaiian resident who was in the water when the Navy was conducting their low frequency active sonar test in Hawaii in March, 1998 was disoriented and nauseous afterward and had to see a physician who diagnosed her with symptoms comparable to acute trauma. (Declaration filed in court, March 25, 1998.) The Navy admitted that this swimmer was exposed to the sonar at 120 dB while she was in the water, far below the operational sonar at 240 dB. In her court declaration this woman also detailed the behavior of nearby dolphins while the broadcast was taking place. The dolphins' behavior, in her view as a naturalist and long term observer of dolphins, was abnormal, including staying close to shore, staying near the surface and vocalizing excessively.

According to the Navy's own test results on the bioeffects of low frequency (100-500 Hz, which is the frequency range of LFA) underwater sound on human divers, at 140-148 decibels a small number of divers rate their aversion to the sound as very severe. At 157 decibels they estimate that at least 20% of divers will immediately abort an open ocean dive. At 160 decibels they say the lung resonance created by LFA may induce "significant decrements in vestibular function." This effect on vestibular function may have caused the stranding of the beaked whales in the Mediterranean (Nature, 1998) when they were exposed to the sonar at 150-160 dB. Lung hemorrhaging was observed in rodents exposed to 170-184 decibels. Above 184 decibels liver hemorrhage and soft tissue damage are likely. The Navy says significant concussion effects are unlikely to occur at levels below 194 decibels but don't explain how they reached this conclusion. According to the Navy's Draft Environmental Impact Statement the sonar sound field around the transmitting ship will be 180 dB up to 1 km away and 150-160 dB up to 160 km away (100 mi) . This means that many marine animals will be exposed to LFA sonar levels capable of causing stranding and, possibly, lung hemorrhaging over large areas of the ocean.

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U.S. Navy's LFA Sonar Tests on Whales (1997-1998)

In 1997 and 1998 the Navy conducted tests of LFA sonar on blue, fin ,grey and humpback whales. The tests were done to develop data for their federally mandated Environmental Impact Statement. As stated above, is important to remember that the tests always used sound levels that had at least 5,000 times less acoustic intensity and 70 times less pressure than the actual sonar. Figure 28 in the "Quicklook" which briefly summarizes Phase I of the testing on blue and fin whales off California (available from Dr. Christopher Clark, Cornell Univ. Laboratory of Ornithology, Ithaca, NY) indicates that blue whales decreased their vocalizations by about 50% and fin whales decreased by about 30% when the LFA sonar sound was on. Since whale vocalizations are believed to be used to attract and find mates, interference with their vocalizations could affect long-term reproductive rates. In Phase II of the tests on grey whales Dr. Peter Tyack reports the whales moved 1-2 kilometers laterally to avoid the 185 dB test sound source. He said the whales started their avoidance over 1 km away from the playback source.

Hawaii Test

LFA sonar was tested on humpback whales in Hawaii during March, 1998. During the one month test period, two cetacean calves (a humpback calf and a spinner dolphin calf) were observed in the test area without their mother by research personnel from the Ocean Mammal Institute. A third lone, melon-headed whale calf was also found in the test area by tourists.

On March 9, 1998 OMI's research team observed and recorded detailed behavioral data on a lone humpback whale calf for four hours from a shore-based research site. The calf breached 230 times (an average of 57 times per hour) and pec-slapped 671 times (an average of 167 times per hour) in four hours. This calf was very agitated and appeared to be exhausted as it got dark. Researchers lost track of the calf at nightfall and could not find it the next day. The Navy's scientists refer to this abandoned calf on pp. 25 and 26 of the "Hawaii Quicklook" and say, "This would be a highly unusual event under normal conditions . . . ." On March 12, 1998 OMI personnel and other individuals on nearby boats observed and photographed a lone dolphin calf about 3 weeks old. On about April 3, 1998 people noticed and later rescued a very dehydrated, lone melon-headed whale calf that was near death. While this calf was discovered a few days after the testing stopped, it was clear it had been separated from its mother for several days.

Separated cetacean calves are very rare. At the Ocean Mammal Institute we have never observed or heard of anyone else observing a separated cetacean calf in nine years of research in the Hawaiian Islands. The fact that we have never seen separated calves before and that all 3 of these lone calves were found during or immediately after the testing in the relatively small LFA testing area north of Kona, and no where else in the Hawaiian islands, suggests there may be a relationship between the LFA sonar tests and the abandoned calves. The sonar tests may cause disorientation (as it possibly did in the stranded beaked whales in the Mediterranean, discussed in Nature) so mothers and calves may become separated and then cannot find each other. Dr. Linda Weilgart, who has studied whale communication for 16 years, in her testimony written for a federal judge to stop the Hawaii LFA sonar test stated, "it is entirely plausible that unnatural acoustic disturbances to which these animals are not adapted could interfere with the crucial mother-calf bond." The sighting of three separated calves in one month in the LFA testing area and no where else, is a very serious warning about the possible effects of LFA sonar that needs further investigation.

Testimony from whale-watch boat captains, an aerial survey done by the Ocean Mammal Institute and data collected by the Navy's shore-based research team all indicate that whales left the LFA test area during the testing. Ocean Mammal Institute did an aerial survey of whales around the Big Island on March 12, 1998 and found no whales around and just north of Keohole Point which was defined by the Navy as the northern area where the LFA test sound would have the highest impact reaching shore. By contrast, aerial surveys done around the Big Island in March, 1993 and March, 1995 showed that the largest concentration of whales was around and just north of Keohole Point, the same area that was devoid of whales in 1998. OMI's aerial survey team did, however, see whales just south and north of the sonar test area.

The Navy's shore-based research team counted significantly fewer whales after March 18, 1998 than during that time period in previous years when the sonar was not being tested. One Kona whalewatch company suspended operations one month earlier than usual because they hadn't seen a whale for 5 days in late March, 1998..

Data from the Navy's Hawaii tests also show that 14 out of 17 or 80% of singing humpback whales tested stopped singing when exposed to the low level sonar. Since singing may have a reproductive function in humpback whales this could affect long term reproductive rates in this endangered species.

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Summary: Cause for Concern

Available evidence indicates that there were effects from the low level sonar tests as follows:

It is important to remember that all these LFA sonar tests were conducted at levels using at least 5,000 less acoustic intensity and 70 times less pressure than the actual sonar which will be deployed at a source level of 240 dB. The highest test level used in Hawaii was 203dB but most of the time it was much lower. On page 5 of the "Hawaii Quicklook" the scientists hired by the Navy say, "The research did not use the full source level of LFA." On p. 6 they say, "...this Phase III research was specifically designed to expose animals to LFA sounds at levels that are not harmful." Even at these low levels, specifically chosen to be not harmful, whales left the test area, three abandoned calves were found in the area and 80% of the whales tested stopped singing. In the Executive Summary they say, " will be difficult to extrapolate from these results to predict responses at higher exposure levels." But now the Navy is doing exactly what their own hired scientists said it would be difficult to do. In their Draft Environmental Impact Statement the Navy concludes that it is safe to deploy the sonar at 240 decibels even though testing was done at sound levels 5,000 times less intense than their deployment level. This is not sound decision-making.

Since LFA sonar was tested on only 4 species of whales for about one month each at an acoustic intensity at least 5,000 times lower than the actual sonar, we know virtually nothing about what impact the real sonar will have on humans, whales, dolphins, fish and other marine life. Are we willing to spend millions, and perhaps billions, of dollars on a system that puts all marine life at risk based on such glaringly inadequate information?

The only responsible course of action is to not deploy this damaging technology.

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Marine Mammal Commission Cautions about LFA Sonar

The Marine Mammal Commission, a federal agency charged with protecting marine Mammals discussed the Navy's LFA sonar in its annual report to Congress (Jan, 31, 1998). In its report the Commission pointed out that if the LFA system were made available for worldwide use as proposed by the Navy, all species and populations of marine mammals, including those listed as endangered and threatened under the Endangered Species Act possibly could be affected. The Commission also pointed out that the Navy's notice about the LFA sonar deployments plan made no mention of the Marine Mammal Protection Act which prohibits harassment of marine mammals as a result of activities such as the proposed sonar. Finally, the Commission pointed out that the possible effects of the LFA sonar on marine mammals could include:

With regard to the last point, the Commission noted that changes in prey species possibly could be caused both directly and indirectly by the LFA sonar transmissions. For example, transmissions conceivably could kill or impair development of the eggs and larval forms of one or more important marine mammal prey species. They might also disrupt feeding, spawning, and other vital functions or cause shifts in distribution patterns of certain important prey species and make some prey species more vulnerable to disease, parasites, and being eaten by other predators.

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