Sound and Fury
Whale deaths blamed on sonar have triggered a heated debate about man-made noise in the sea
Shipping is another big source of acoustic smog. Supertankers, icebreakers, cruise ships, even tugboats and ferries have helped boost the level of ambient noise 10-fold in the past 40 years in the frequency band that whales use to communicate, says John Hildebrand of the University of California-San Diego and the Scripps Institution of Oceanography. Many scientists suspect that the noise has shrunk the range over which the big whales can hear one another from about 1,000 miles to 100.
Many industries that inject a lot of noise into the ocean have gotten used to operating in an out-of-sight, out-of-mind fashion, says Cornell's Clark. But he's not entirely despairing. Now that regulators are coming to grips with the idea that noise can be a pollutant, innovative people will begin devising ways to quiet the cacophony under the seas.
Depth charge
Potent beams of sound from Navy sonar, used to detect submarines, apparently injured and confused beaked whales, leading these small cetaceans to beach themselves and die. Beaked whales can dive to depths of almost a mile to feed on squid; no one knows how deep they were when they were injured.
In this 3-D image, hemorrhages (red) are evident in the head of an injured whale.
Collateral damage?
Dozens of multiple strandings of beaked whales have been reported in recent decades. At least nine occurred when naval or other ships were said to be maneuvering nearby:
DATE LOCATION NUMBER
April 1974 Bonaire 4
Dec. 1974 Corsica 3
Feb. 1985 Canary Islands 13
Nov. 1988 Canary Islands 3
Oct. 1989 Canary Islands 25
May 1996 Greece 12
March 2000 Bahamas 14
Sept. 2002 Canary Islands 15
Sept. 2002 Mexico 2
advertisement
