Effects of Low Frequency Active Sonar (LFAS)

  1. The Navy and NOAA issued a joint report in December 2001 ( on the mixed species mass stranding that occurred in the Bahamas in March, 2000. The report concludes that the strandings and internal injuries suffered by these animals were caused by the Navy’s use of intense mid-frequency active sonar in the area. This report also indicates that the stranded whales were exposed to sound pressure levels well below the 180 dB criterion now being used by the Navy as the "safe" level for marine mammals.

  2. Mass strandings of beaked whales involving more than one species are very rare. Only 9 such incidents have been recorded and all have been associated with naval maneuvers nearby. (Initial evidence was compiled by a beaked whale researcher at the Smithsonian Institution and presented at an IWC workshop in June, 2000. Additional evidence was presented at a workshop on unusual marine mammal mortalities in February, 2001 by Terri Rowles.)

  3. The FEIS focuses on possible auditory effects of LFAS on marine mammals such as deafness. However, sound also can have nonauditory physiological effects. Scientists recently have discussed two possible nonauditory effects of intense sound on marine mammals.

    1. Ken Balcomb, the marine mammal scientist who discovered the Bahamas stranding, suggested in a letter to the LFAS Program Manager (February, 2001) that the beaked whales stranded from nonauditory physiological impacts caused by acoustic resonance of the LFAS signal in their cranial airspaces. This resulted in the hemorrhages observed during the necropsies. (The frequencies of LFAS and mid-frequency sonars match the cranial airspace resonance frequencies of beaked whales at normal foraging depths.) This evidence was recently presented, analyzed and affirmed by a number of experts in the fields of marine mammalogy and bioacoustics. Although resonance effects are acknowledged by the Navy as a potential problem for humans, it is not discussed in the FEIS with regard to marine mammals or most other species.

    2. A paper published in the Journal of Theoretical Biology in November 2001 by three Navy scientists (Houser, Howard & Ridgway) suggests that moderate levels of sound (as low as 150 dB) may cause embolism and tissue rupture in the supersaturated blood and tissues of marine mammals by activating the growth of microscopic bubbles. This nonauditory effect of sonar is independent of the frequency of the sound wave (mid-frequency and low frequency sounds can activate bubble growth). The FEIS does not address the potential for injury from sound-activated bubble growth in marine mammals.

  4. Ken Balcomb has reported that the Bahamas event resulted in the entire resident population of beaked whales disappearing from his study area due either to abandonment or death. Thus, the Bahamas naval exercises did not have only transient effects, but affected an entire population of beaked whales. The Navy/NOAA report on this stranding does not mention the disappearance of an entire population of beaked whales.

  5. In a preliminary report on the Bahamas stranding, the Navy suggested that LFAS operating in the same region with other systems can produce cumulative and synergistic effects. New evidence based on environmental assessments on other Navy projects and documents obtained from abroad on deployment of active sonars by foreign navies indicates the possibility for adverse cumulative and synergistic effects that are not addressed in the FEIS. (See, for example, Jane’s Defense Weekly 21 Nov. 22, 2000.)

  6. New stock assessment of the Northern right whales by NMFS (2000) indicates that the feeding and nursery area of one-third of reproductive females is unknown and may occur in deeper water. This increases the risk that the endangered northern right whale population in the North Atlantic (approximately 300 individuals) could be exposed to sound pressure levels greater than the Navy’s presumed "safe" 180 dB criterion, with potentially adverse effects. As indicated in #1 above, new evidence from the Bahamas stranding indicates that exposure to significantly less than 180 dB can result in strandings and deaths.

  7. Findings presented to the National Research Council committee on ambient noise by researchers from the Hawaii Institute of Marine Biology (October, 2001) using new electro-physiological methods for measuring hearing loss in marine mammals, indicate that hearing loss in bottlenose dolphins may occur to a greater degree and at lower exposure levels than the Navy’s own research cited in the FEIS indicates. A study of hearing threshold shifts in pinnipeds at Long Marine Laboratory also does not support the Navy’s auditory impacts analysis in the FEIS.

  8. Evidence concerning the present and future availability of new and advanced passive sonar technologies (such as Advanced Deployable Systems tested off California, Robust Passive Sonar (RPS) and towed arrays equipped with Acoustic Rapid Commercial-off-the-shelf Insertion (ARCI) processing) which have the potential to locate quiet submarines without harm to marine life are not discussed in the FEIS. (See RADM Malcolm I. Fages and RADM J.P. Davis, Statement before the House Armed Services Committee Military Procurement Subcommittee (June 27, 2000) and Presentation of Dr. Thomas J. Green, Defense Advanced Research Projects Agency, to Department of Defense (Sept. 6-8, 2000) noting the potential effectiveness of a "Robust Passive Sonar" system apparently in development at DARPA).


Prepared by: Marsha L. Green, Ph.D. Ocean Mammal Institute

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