Navy sonar affecting whales
By Marc Kaufman
Go to the original Washington Post article
“Navy Sonar May Give Whales the 'Bends'
Condition Similar to Decompression Sickness Found in Mammals Beached on Canary Islands”
8th October 2003
High-powered sonar from Navy ships appears to be giving whales and other marine mammals a version of the bends, causing them to develop dangerous gas bubbles in some tissues and blood vessels and to beach themselves and die, according to a study published yesterday in the journal Nature.
Reporting on beaked whales that were stranded in the Canary Islands soon after an international naval exercise last year, researchers for the first time found a condition similar to decompression sickness in 10 of 14 dead animals.
The new data begin to explain how and why high-decibel mid-frequency sonar used by the U.S. Navy and other military fleets appears to cause some deep-diving marine mammals to die. Although the bends was previously unheard of in whales, dolphins and porpoises, the British and Spanish researchers concluded that a marine mammal version of decompression sickness was "the most likely cause" of the Canary Island strandings.
"This is the best data we've ever seen from a sonar-related stranding," said Roger Gentry, coordinator of the National Oceanic and Atmospheric Administration Fisheries Acoustics Team. He said NOAA will hold a workshop this year with the authors and others in the field to assess the new information and try to reach scientific conclusions.
The new research from the Canary Islands suggests two possible explanations for how the gas bubbles harm the whales. One is similar to the way humans get the bends: The whales panic at the sound of the loud sonar noises and rise too quickly from deep water. As they rise, nitrogen bubbles can be formed from the rapid change in pressure and cause the bends. The other hypothesis involves bubble formation caused directly by the sonar on gas nuclei, or bubble "precursors," in whale tissues that are already highly saturated with nitrogen.
Gentry said the scientific community remains sceptical that rapid ascents are causing the bubbles to form. "From an evolutionary point of view, it does not seem likely," he said. "Whales have been diving like this forever, and should have evolved mechanisms so they wouldn't succumb to decompression."
The Canary Island strandings and research involve mid-frequency (or pitch) sonar coming from Spanish-led, international naval manoeuvres that included only one American destroyer. But they could affect a contentious debate over the U.S. Navy's desire to deploy very loud low-frequency sonar around the world to detect "quiet" submarines. That effort was stopped in August in California by a federal magistrate who said the government had violated environmental laws in giving the Navy permission to deploy the new sonar globally.
"We know there is a connection between military sonar and strandings, and now we're making progress on the physical mechanism causing them," said Joel R. Reynolds, an attorney with the National Resources Defense Council, which sued the government over the low-frequency sonar. "This is very compelling scientific evidence."
Lt. Cmdr. Joseph A. "Cappy" Surette, a Navy spokesman, said officials are still studying the Nature article. But he said the Navy takes many steps to avoid harming sea creatures and that the new sonar technology is necessary.
"Submarines are becoming an increasingly serious threat to the U.S. Navy," he said. "Diesel submarines have become increasingly difficult to detect and are proliferating around the world."
He also said that "there is no evidence of any negative impact on marine mammals" in areas where the new low-frequency sonar has been tested.
The legal problems faced by the new Navy sonar system, called the Surveillance Towed Array Sensor System -- Low Frequency Active (SURTASS-LFA), have upset some in Congress and helped spur successful efforts to pass legislation to limit the reach of environmental laws that affect the Defense Department. The legislation, part of the Defense Department appropriations bill, is in conference. The House language broadly exempts the Defense Department from provisions of the Endangered Species Act and the Marine Mammal Protection Act, while the Senate language is considerably less limiting.
Several mass beachings of whales and dolphins have been tied to high-decibel sonar since the phenomenon was first identified in 1996, and Navy researchers are going back to see whether other strandings can be connected with nearby Navy sonar use.
Whales and other marine mammals are highly sensitive to sound and use it to communicate. Different species hear at different frequencies, and so are affected by various kinds of sonar. The low-frequency sonar that the Navy wants to use around the globe operates at the sound level used by the largest, and some of the most endangered, whales.
The whales stranded in the Canary Islands are beaked whales, the same kind killed in a similar stranding involving sonar in the Bahamas in 2000. Beaked whales are relatively small and dive deeper than most to feed on squid.
The Navy initially said that its sonar had no connection with the 2000 stranding, but a later inquiry ruled out all other possibilities and concluded the sonar most likely caused the deaths.
The research published yesterday in Nature was conducted by scientists at the Zoological Society of London and the University of Las Palmas de Gran Canaria in Spain. The English researchers also reported that six dolphins and one beaked whale that had stranded along British shores between 1992 and 2003 had gas bubbles in their blood vessels.