Whale Deaths Halt Sonic Experiment : Mammals: Three humpback carcasses are found days after ocean floor loudspeaker is turned on. Scientist denies that sound project--a global warming study--is to blame.

A controversial ocean sound experiment off Half Moon Bay has been halted indefinitely after the discovery of three dead humpback whales in the area, Scripps Institution of Oceanography officials said Wednesday.

The whale carcasses were found just days after the ocean floor loudspeaker was turned on repeatedly, apparently before required steps were taken to ensure the safety of the whales and other marine life. The cause of the whales’ death has not been determined, but Scripps scientists insist that their repeated 20-minute, 195-decibel transmissions were conducted properly and are not to blame.

Critics of the project accused the scientists of acting in “bad faith” by broadcasting the low, rumbling sound without monitoring the effect on marine mammals as required under their federal permit.

“What is most disturbing is that Scripps violated the conditions of their permit and turned on the sound source,” said Sara Wan, vice chairwoman of the League for Coastal Protection. “None of the protocols that were agreed to were followed.”

Three humpback whales dying in the same area at the same time is very unusual, and because of the circumstances, the cause of their deaths may be difficult to pin down.

One of the animals washed up on popular Stinson Beach north of San Francisco on Nov. 4 and was buried there before a necropsy could be performed. The other two whales were found a few days later at sea but efforts to tow them to shore for analysis were unsuccessful.

Andrew Forbes, manager of Scripps’ Acoustic Thermometry of Ocean Climate experiment, said the animals could very well have died before the loudspeaker tests were conducted between Oct. 28 and Nov. 2. It is most likely, he added, that they died of old age or were poisoned when they ate anchovies that contained high levels of toxins from an algae bloom.

“There is zero possibility that a 195-decibel source of transmission could kill a humpback whale,” Forbes said. He noted that blue whales routinely make noises that loud without resulting in the deaths of humpback whales.

But other experts said a lack of monitoring during the tests makes it impossible to determine if the sound source affected the whales--or other animals in the region. As a result, no one in the scientific community can definitively clear the Scripps project of responsibility.

“My personal feeling is that it’s not likely that the sound source caused the death of these animals,” said Peter Tyack, an associate scientist at the Woods Hole Oceanographic Institution and a member of an advisory board for the Scripps experiment. “But the death of three humpbacks in a few days is a rare and serious event, and we know so little about the impact of noise on marine mammals that we have to be cautious.”

The sound experiment is intended to study global warming by broadcasting transmissions through the deep waters of the Pacific Ocean to receivers as far away as New Zealand.

The proposal touched off a firestorm of controversy last year after some whale experts contended that the broadcasts were loud enough to cause auditory damage to deep-diving whales. The impact could be serious because whales are believed to navigate and find food largely by sound.

Scripps scientists argued that their sound would not harm whales and would be less intrusive than many other man-made noises in the ocean, such as cargo ships and seismic air guns used in oil exploration.

Eventually, they agreed to move the site of their loudspeaker from a location in a marine sanctuary off Big Sur to a site farther to sea off Half Moon Bay. They also agreed to conduct a comprehensive study of the effect of the broadcasts on marine mammals and other sea life before beginning the global warming phase of the project.

But after the loudspeaker was installed on the ocean floor, the scientists tested the system by broadcasting the sound 12 times over four days without initiating the elaborate marine mammal research program they had agreed to.

When UC Santa Cruz marine biologist Dan Costa, who heads the marine mammal research program for Scripps, heard of the first whale death, he immediately called a halt to the sound transmissions.

The broadcasts are unlikely to begin again until reviews of the whale deaths are conducted by the National Marine Fisheries Service, which gave Scripps its research permit, and the advisory board that oversees the project.

“We are in a very difficult situation in that we cannot tell for sure why these whales died,” Costa said. “Until everyone is satisfied, we will not proceed.”