To Noisy For Whales

                                                          By: Paul Kelly

2000-Sixteen beaked and minke whales beached in the Bahamas. Researchers pushed 10 back to sea. The six who died were bleeding around their inner ears and their brains.

2002-Forteen whales beached and died in the Canary Islands.

2005-Thirty-seven whales from three different species beached on North Carolina's Outer Banks.

    Each of these sad incidents occurred after the military used sonar nearby. Military Sonar, used by the U.S. Navy and other nations to detect submarines, can produce bursts of sound of over 215 decibels. The sound travels hundreds of miles through the oceans depths. The sonar bursts are as loud as undersea earthquakes and volcanic eruptions, but they may be more dangerous to animals because the sound is concentrated at the same frequency, similar to beeps sounding on one note. Scientists at the International Whaling Commission believe that sonar is very likely killing the whales.

    Studying this problem is not easy. Whales travel all over the world's oceans and dive to great depths, to places where people can go only with sophisticated and expensive equipment. And whales beach themselves for reasons we don't understand.

    But we know that Earths oceans are getting louder. Human noise in the ocean off Southern California doubled at least twice between 1950 and the late 1990s. Most of this noise is from tankers and container ships that carry products around the globe. The number of these large ocean vessels is expected to double in the next 20 to 30 years. Many human activities, from riding jet skis to bridge construction, add to ocean noise, making it harder for whales and other marine mammals to hear each other. The loudest man-made sounds in the ocean are explosives, followed by air guns used to explore the ocean crust for oil and natural gas. At up to 250 db, these are nearly as loud as lighting striking water. Their booms last more less than a second but may be repeated every 15 seconds for months at a time. The sound can travel thousands of miles.

    We also know that whales and other marine mammals depend on hearing to survive. Whales sing complicated songs to communicate with each other. Many whales, like bats, use sound to echolocate and navigate through the oceans.

    After the beaked whales beached themselves in the Bahamas in 2000, whale experts and conservation groups called for an investigation. The Navy asked a group of scientists to examine the damage to dead whales' ears, study the ocean currents in the area where they beached, and look at sonar equipment on five different ships and a submarine that had been doing training exercises near the beach. The whales died because they dried out on the beach, but the injury to their ears may have frightened them and made them unable to find their way.

    Though the scientists still could not identify exactly how the sonar damaged the whales' ears, they couldn't find any other likely causes and concluded that the sonar was to blame.

    When scientists examined the whales that beached in the Canary Islands, they found small air bubbles in their tissues. One team investigated whether the frequency of the sonar signals led resonance and caused very small gas bubbles to grow. Others suggested that these deep-diving whales surfaced to rapidly, and got the bends as a human diver would.

    In May 2004, several agencies of the U.S. government brought together scientists to discuss shipping noise and its effects on marine mammals. They recommended more study. Scientists need to look at how each species hears, how it uses sound, and how it responds to various types of noise. They need to map the overall level of noise in the ocean, where noise is concentrated, the different source of ocean noise, and how much each contributes to potential problems. Scientists can also study how to reduce ocean noise and how to protect sensitive species from the most dangerous forms of noise.

    There are some helpful solutions. For instance, 83 percent of shipping noise in the oceans comes from propellers. Most propellers churn up air bubbles that then collapse in the water,  sounding like thousands of hands clapping. Propeller "capitation", as it is called, wastes energy, so improve propeller design can make the oceans quieter as well as increase ships' fuel efficiency. To protect whales and other sea mammals, the U.S. Navy sometimes listens for marine mammals with sensitive passive sonar devices, uses annoying pings to warn them away, and only gradually ramps up the full power of the active sonar-giving animals the chance to move to safety.