WASHINGTON - Navy sonar may be giving whales a never-before-seen version of the illness known as "the bends," leading them to be stranded and to die, according to a new study in Thursday's edition of the scientific journal Nature.
The findings could strengthen the hand of environmental groups trying to force the world's navies to limit or stop their use of sonar during sea exercises. The U.S. Navy and the Natural Resources Defense Council this week are negotiating such limits in an effort to settle an NRDC lawsuit.
In the Nature article, scientists report finding gas bubbles in the organs and blood vessels of 10 beaked whales that stranded themselves along Spain's Canary Islands in September 2002. They beached themselves about four hours after the beginning of sonar activity nearby during an international naval exercise.
A whale pops its tail out of the water. (KRT Photo/Howard Shapiro)
"Our findings suggest that naval sonar could be killing whales," said study co-author Antonio Fernandez, a pathology professor at the University of Las Palmas de Gran Canaria in Spain. "The protection of the whales is a responsibility of everyone."
Other top whale scientists were skeptical.
Darlene Ketten, a senior whale biologist at the Woods Hole Oceanographic Institute and an ear, nose and throat professor at Harvard Medical School, said whales don't get the bends.
"We expect that these animals over 50 million years evolved to avoid problems resulting from diving," Ketten said. Other stranded whales have not shown symptoms of the bends, she added.
In addition, whales don't absorb the nitrogen needed for the bends to form, said Daniel Costa, a marine biologist at the University of California at Santa Cruz.
The U.S. Navy, which is reviewing the Nature study, said more research is needed. The Navy defends the use of sonar as key to American security and has sought an exemption from the 31-year-old federal Marine Mammal Protection Act so it can use sonar.
"Imposition of restrictions on use of mid-frequency sonar prior to a comprehensive study of the issue could compromise the safety of America's men and women who serve aboard Navy ships," said Navy spokesman Lt. Commander Joseph "Cappy" Surette. Even if further research implicates sonar, the number of marine mammals killed by sonar is small compared with those killed by fishing nets, he said.
Navies have been using sonar - sound waves that travel through water - since World War II to find targets. Sonar mimics the systems that whales use to find prey.
A report by the U.S. Navy and the Commerce Department about a mass whale stranding in the Bahamas in 2000 concluded that Navy sonar was one of the chief causes of the whales' deaths. The National Academies of Science in February found that beaked whales often strand and die after use of naval sonar, but concluded that there was not enough evidence to blame sonar alone for strandings.
Decompression sickness, often called "the bends," occurs when scuba divers surface too quickly after lengthy dives. It's caused when nitrogen gas, which has been absorbed into the body at high pressure, is quickly released upon surfacing and forms painful and, at times, deadly bubbles in the body. It's similar to opening a bottle of carbonated soda.
The Canary Islands cases are the first large-scale evidence that something similar to the bends is at work, said study co-author Paul Jepson of the Zoological Society of London. Those whales, most of them Cuvier's beaked whales, had gas bubbles in different parts of their bodies. The bubbles were worst in their livers, where some bubbles exceeded 2 inches in diameter, according to the study.
Jepson said he didn't know exactly how whales got this condition. There are two possible ways: Either the whales are disturbed by the sonar and rise much more rapidly than normally, or the sonar could somehow cause bubbles to form.
"It's just one more piece in what's a very long line of evidence that the use of intense Navy sonar around the world is a serious environmental program," said NRDC attorney Andrew Wetzler.
NRDC sued the U.S. Navy to stop or alter its plans to use low-frequency sonar in the Pacific near whales. Most studies, including the Canary Islands one, were based on mid-frequency, not low frequency, said Surette. The Navy wants to use low-frequency sonar to track quiet enemy diesel submarines, he said.
"In recent tests this system has proved itself extremely effective at identifying potentially hostile submarines," Surette said. "An independent scientific research program concluded that the Navy could test and train with (the low-frequency sonar) without significantly affecting marine mammals."
In June, a federal judge-magistrate in San Francisco ruled that the Navy must limit its plans for low-frequency sonar exercises.
The Navy is also examining dead whales and porpoises after a mass stranding last May in Everett, Wash., days after Navy sonar use.
Knight Ridder Newspapers researcher Tish Wells and correspondent Glennda Chui contributed to this report.
Copyright 2003 Knight-Ridder