|FYI — January 2004|
|By Brad Dunn|
Sonar Side Effect
According to marine biologists, it appears that not only can these aquatic animals suffer the same type of decompression sickness that has long plagued human scuba divers, but that nautical sonar can directly provoke the illness.
In October researchers published results from a study of stranded whales and dolphins in the journal Nature. The study reported that the scientists found tiny nitrogen bubbles throughout the mammals’ tissues similar to those that cause the bends. Scientists further reported finding “evidence of acute and chronic tissue damage in stranded cetaceans, challenging the view that these mammals do not suffer decompression sickness.” It was the first time the illness had been linked to mammals, and scientists speculate that sonar is the culprit. Military vessels often use sonar to detect submarines. The sound blasts, which are far more intense that those used by recreational boaters to measure depth, have already been found to affect the migration routes of whales and dolphins.
“It is widely accepted that there is a link between naval sonar use and mass strandings, predominantly of big whales,” the researchers state. The theory is that strong sonar blasts confuse and frighten the marine mammals, causing them to dart to the surface more quickly than they should. They then apparently undergo a rapid decrease in pressure of both the water and air in their bodies, which causes the formation of deadly nitrogen bubbles in the bloodstream that is consistent with decompression sickness.
The evidence is abundant. A mass stranding occurred last year in the Canary Islands immediately following a large naval drill. Another in the Bahamas in 2000 was linked to a sonar system.
Now, for the first time, sonar use may prove fatal to the largest animals on the planet. Or, as the scientists put it, “Acoustic factors could be important in the aetiology of bubble-related disease and may call for further environmental regulation of such activity.”
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This article originally appeared in the December 2003 issue of Power & Motoryacht magazine.