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Sonar Side Effect
The long-held assumption that whales and dolphins cannot get the bends just got bent.

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.”

Things We Like
If you get embarrassed pulling out a big ol’ map while on a cruise or simply dislike lugging around a 300-page tour book, check out the InsideOut Guides. On one side a map unfolds like an accordion, while on the other a booklet has the crucial info you need about that city. Available for cities around the globe, the guide also comes with a pen and a compass. PMY managing editor Eileen Mansfield recently gave the Barcelona edition a good trial run and decided it was the next best navigational device after her chartplotter. They’re perfect for cruises and boat shows, and they fit right in your back pocket. Published by Compass Maps, the guides are available at Rand McNally and Brookstone, among other stores and Web sites.

502
Average number of people that attend a Coast Guard Boating Safety Course each day. Source: U.S. Coast Guard

January Calendar
Dec. 27-Jan. 4. The New York National Boat Show in New York City. (212) 984-7000. www.discoverboating.com/newyork.
8-11. The Boat Show in San Diego, California. (858) 274-9924. www.discoverboating.com/sandiego.
14-18. The Boat Show in Atlanta, Georgia. (770) 951-2500. www.discoverboating.com/atlanta.
17-25. Boot 2004, the 35th-Annual International Boat Show in Düsseldorf, Germany. (312) 781-5180. www.mdna.com.
22-25. Central Florida Boat Show in Orlando, Florida. (407) 298-1167. www.boatshowflorida.com.
24-31. Chesapeake Bay Boat Show in Baltimore, Maryland. (212) 984-7000. www.discoverboating.com/chesapeake.

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