Sound and Fury
Whale deaths blamed on sonar have triggered a heated debate about man-made noise in the sea
Quiet, please. The Navy itself has acknowledged that the earsplitting, 235-decibel-plus screeches emitted by its sonar played a role in the Bahamas strandings. But the Navy and others who inject loud sounds into the ocean now face wider concerns that could mute their equipment, at least for now.
Last October, an environmental organization filed suit against the National Science Foundation, which funds the seismic research vessel that was operating in the Gulf of California, for failing to conduct a review of the blasts' impact on marine mammals. A judge issued a restraining order halting research with the towed array until the analysis could be completed. The Navy has come under fire from environmentalists over a low-frequency sonar system it is developing to detect a new generation of quiet, diesel-electric submarines. The Navy says the system has never harmed whales, but last month a judge limited tests of the system to a 1 million-square-mile zone of the Pacific off the Philippines and Japan pending a trial. Noise, it seems, has joined toxics, oil spills, and overfishing as a recognized threat to sea life, even though the extent of the danger is still unclear.
Ken Balcomb's quick action on March 15 helped pin down the link, long suspected, between sonar and strandings. After getting word of a third beached whale that day, Balcomb put in a call to Bob Gisiner, manager of marine mammal science and technology programs at the Office of Naval Research in Washington. To document the sounds that the whales had been exposed to, Balcomb urged him to save acoustic records from Navy hydrophones positioned in local waters. When Balcomb said he would try to freeze the ears of whales that died, Gisiner suggested that he cut off whole heads instead. More detailed dissections could be conducted, Gisiner said, by other whale-acoustics scientists.
The upshot of the investigation was a report issued by the Navy and the Department of Commerce that described hemorrhages "consistent with acoustic trauma" in and around the ears of the dead beaked whales. The report concluded that while "intensive active use of multiple sonar units" was the most reasonable explanation for the injuries, the sounds the animals heard were not intense enough to have killed them directly. Instead, the pings drove the whales up onto beaches, where they died from overheating and cardiovascular collapse.
Few scientists dispute that it was the whales' response to the noise that did them in, not the noise itself. The Smithsonian's Potter points out that a lethal blast would have caused all kinds of animals--from fish to pygmy whales--to wash ashore. Darlene Ketten, a biologist with the Harvard Medical School and Woods Hole Oceanographic Institution, performed three-dimensional CT scans on the whales' heads to look for trauma. She says that had the pings been at deadly levels she would have seen "blowouts of membranes in the inner and middle ear," among other injuries. If the whales hadn't beached themselves, she says, "I would have expected them to recover."
Some scientists take issue, however, with what they argue is the report's implication that the Bahamas strandings were a rare misfortune. The report suggests, for example, that unusual water conditions that day may have channeled the pings and that beaked whales are especially sensitive to sonar. Narrowing the focus of concern in that way is unwarranted, asserts Lindy Weilgart of Dalhousie University in Nova Scotia, who studies sperm whales. It "really oversteps what we know about whale hearing and behavior."
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