Federal investigators have concluded that U.S. Navy ships testing an undersea surveillance system in the Bahamas were the likely cause of mysterious mass strandings of whales and dolphins two years ago.
The Navy's midrange frequency sonar -- the underwater equivalent of radar -- was the only source in the region that could have contributed to the acoustic trauma, a hemorrhaging around the sea creatures' ears, a study found.
Seven animals died, and 10 others that washed up were moved back into the water.
The findings by a National Marine Fisheries Service team last week are certain to arouse further opposition to a Navy proposal to deploy a global system using low-frequency sonar to hunt for enemy submarines.
The Natural Resources Defense Council, the Humane Society and Defenders of Wildlife sued the Navy in U.S. District Court on Sept. 10 over the project, contending that it lacked the required environmental reviews of its sonar tests in coastal waters.
The Navy has said its technology poses no significant hazard to marine mammals. Noise levels drop below a threshold considered safe, the Navy said, as long as whales are at least a kilometer away from the sound source. With Navy observers posted as underwater scouts, the system could be shut down if any animals strayed too close during operation, officials said.
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