By RACHEL X. WEISSMAN
April 10, 2001
Last spring Kenneth Balcomb, a marine mammalogist, woke to find an unsettling situation outside his Abaco Island home in the Bahamas: a 16-foot Cuvier's beaked whale weighing some two tons stranded in knee-deep water.
With the help of several volunteers, Mr. Balcomb, who heads the Center for Whale Research in Friday Harbor, Wash., tried to push the animal out to sea. After the fifth attempt, the disoriented whale stopped turning toward shore and continued into the open ocean. But that was only the start. Over 15 hours beginning March 15, about 16 whales and a dolphin became stranded on the beach and in shallow waters around the northern Bahama islands. Most were pushed back into the sea by Mr. Balcomb and volunteers, who had gone to the Bahamas to observe the whales as part of a program for the Boston- based Earthwatch Institute, a nonprofit organization that supports scientific field work. Still, the dolphin and six whales died. It was one of the largest strandings of beaked whales on record. Five days later the United States Marine Fisheries Service, at the request of the Bahamian government, sent biologists to perform necropsies. They found hemorrhaging around the brain and ear bones. On the one-year anniversary of the strandings in March, a task force from the agency and the United States Navy said that it was highly likely that the stranding was caused by sonar transmissions from Navy ships that were performing antisubmarine exercises nearby.
Now some biologists and environmental groups fear that such mass strandings will become more common if the Navy wins approval for a sonar program it wants for detecting submarines. Called the Surveillance Towed Array Sensor System, or Surtass, it would consist of four sonar- equipped ships able to sweep 80 percent of the world's oceans.
The Navy, which must have a permit from the marine fisheries service before it can proceed, discounts claims that what happened in the Bahamas could result from Surtass, because the sonar used during last year's strandings operated on a middle frequency and its Surtass program would use a low frequency. Both systems, however, transmit sound waves that bounce off objects and send information back to the listener. In the proposed system, transmissions could be as loud as 230 decibels, roughly the noise of a rocket taking off. The Navy proposes using observers and monitoring instruments to make sure no marine mammals are within a kilometer. Beyond that, the sound would have dissipated to at most 180 decibels, a level at which some scientists believe physiological damage occurs. The sound would join a chorus of others that contribute to rampant noise pollution in the oceans. Contributors are the babble of engines from industrial vessels, air guns used in oil and gas exploration and sonar impulses used for a variety of purposes. Whales are more susceptible to interference from sound than are many other mammals because of their heavy reliance on it for primary activities like feeding, communication, navigation and nursing.
"Ocean noise pollution is akin to humans living in a world of increasing smog," said Dr. Lindy Weilgart, a bioacoustician who studies whales and sound at Dalhousie University in Halifax, Nova Scotia. "The windows of opportunity in which whales can communicate with a specific group member or find prey are increasingly limited because of noise pollution," Dr. Weilgart said. "And most whales are endangered and having a hard time anyway."
The Navy's Surtass plan is opposed by advocacy groups like the Natural Resources Defense Council, which pressed the Navy to show how its project would affect the environment. Because of a dearth of data, the Navy began research on low- frequency sonar's effect on large whales, which communicate at that level. The marine fisheries service is using the data in reviewing the Navy's permit request and will accept public comments until May 18.
Dr. Christopher W. Clark, director of bioacoustics research at Cornell and one of the main investigators for the Navy's Surtass research, said that one phase of that program tried to find out the effects of exposure to sonar levels higher than 120 decibels, a level that certain whales have been observed to avoid.
About 200 miles off San Diego, where blue whales and fin whales feed, the Navy tested its sonar in the summer and early fall of 1997 and found that whales showed no reaction at 150 decibels. "That was encouraging and even surprising," Dr. Clark said. "We had all predicted that by 140 for sure you'd see a reaction." Because of bad weather, no higher levels were tested.
But Mr. Balcomb noted that the Navy was proposing using even higher levels around the whales, and he said the Navy had not studied enough species. "They used only low-frequency communicators because that's what they thought would be affected," he said. "My point on resonance is that its effects have nothing to do with hearing."
Dr. Weilgart said that the Navy should instead be looking at data on strandings that correlate with nearby military operations using sonar. The Navy and regulators from the marine fisheries service who are reviewing the permit proposal say the two sonar systems, low- and mid- level frequency, are so different that it is entirely unfair to link the two.
The midlevel, non-Surtass sonar implicated in the Bahamas strandings can be heard over short distances by many marine mammals, particularly smaller ones. The low- frequency sonar proposed in Surtass, on the other hand, is audible over hundreds of miles to far fewer animals and is emitted at the same frequency used by large whales like the famous singing humpback. But Mr. Balcomb, in whose back yard this all began, holds fast to his claim that what caused the hemorrhaging in the Bahamas whales was not sound's effect on the whales' hearing but on resonance effects in their air cavities. In a recent letter to the Navy, Mr. Balcomb used calculations by the Navy's own physicists to show that both low and middle frequencies can create resonance effects in whales' air cavities. He surmised that low-frequency sonar could cause the same injuries probably caused by the midlevel sonar during the Bahamas strandings.
Mr. Balcomb also said that the visible damage of last spring was only part of the picture. None of the 50 Cuvier's beaked whales that frequented the Bahamas year round have been seen since the strandings. He presumes that all had died.