Boulder CO (UPI) Feb 09, 2005
Most people know the modern world is a noisy place, but they might not be aware the oceans have gotten to be considerably noisy as well - and they are getting noisier, to the detriment of whales and other marine mammals.
Ship traffic alone in the oceans is increasing noise levels by 3 decibels to 5 decibels per decade, according to Roger Payne, a biologist and founder and president of the Ocean Alliance.
Payne, who has studied the behavior of whales for nearly 40 years, discovered that humpback whales sing songs, and that the sounds of finback and blue whales can carry great distances underwater.
"The sounds made by whales propagate across oceans," Payne told UPI's Blue Planet. "Blue whales make a low moan, which would be heard thousands of miles away - before the ocean was polluted with ship traffic."
Payne pointed out that 99.999 percent of the evolution of whales took place without any sounds from ships.
"Now they are just roaring everywhere," he said. "In the North Atlantic, noise has reduced the area in which two finback whales can hear each other by four orders of magnitude" - or 10,000 times.
Undersea oil exploration is adding to the problem. The industry uses powerful air guns to search for hydrocarbons lying deep beneath the ocean floor. These ship-towed arrays explode high-pressure air against a diaphragm to send sound shock waves through the water and the ocean floor. Researchers listening for whales in the mid-Atlantic have heard this seismic testing being conducted off the coast of Mauritania in Africa, thousands of miles away.
Still more noise comes from the U.S. Navy's sonar equipment, used to detect submarines. There is considerable evidence the mid-range sonars the Navy employs drives beaked whales onto beaches.
"There is sufficient evidence to conclude that high-intensity sounds are harmful and, on occasion, fatal, to marine mammals," Payne said.
Following exposure to sounds from sonar or air guns, beaked whales may swim rapidly to a beach, and die there of overheating if not returned to the sea by human intervention.
The Navy is also developing low-frequency radars to listen for quiet diesel submarines used by Russia, China and others. There is considerable controversy over whether these radars will harm marine mammals. A federal court already has blocked their use in the Pacific basin.
According to a report on ocean noise prepared by the Natural Resources Defense Council, research by the Navy's low-frequency radar program and underwater loudspeakers deployed by the Scripps Institute found "gray whales exposed to 120-decibel sounds tend to deviate from their migration paths and ... sperm whales faced with higher levels can fall silent for hours or days; yet the significance of these reactions is uncertain, and their cumulative impact, like those of the rise in ambient noise, is unknown."
The NRDC report added that each loudspeaker in the radar system's wide array can generate 215 decibels, which is as intense as the noise produced by a twin-engine fighter jet at takeoff. Some mid-frequency sonar systems can put out over 235 decibels, as loud as the giant Saturn V moon rocket at launch.
Evidence of the harm such a barrage of sound can do began to surface in March 2000, when members of four different species of whales stranded themselves on beaches in the Bahamas after a U.S. Navy battle group had used active sonar in the area. Investigators found the whales were bleeding internally around their brains and ears. Although the Navy initially denied responsibility, the government's own investigation established with virtual certainty the strandings were cause d by the use of active sonar. Since the incident, the area's population of Cuvier's beaked whales has all but disappeared, leading researchers to conclude they have either abandoned their habitat or died at sea
"The Navy's Scientific Research program never tested the full source level of (Low-Frequency-Active sonar) on marine mammals," wrote Marcia Green, head of the Ocean Mammal Institute in Reading, Pa., of the incident. "The Navy has not followed the advice of their own hired scientists and has inappropriately extrapolated to conclude that LFAs is safe to deploy at levels of at least 5,000 times more acoustic intensity and 70 times more pressure than test levels."
Lt. Christine Ventresca, a Navy spokeswoman, told Blue Planet that in 1996 a $2 million study, conducted by leading scientists, concluded the potential impact from the Surveillance Towed-Array Sensor Low-Frequency Active, or SURTASS LFA, was negligible, both in direct effects and in changing biologically important behavior such as mating.
"Despite what you've been told, sonar has never been connected with any marine mammal strandings," Ventresca added. "It was not in use when marine mammals were stranded in the Bahamas."
The National Marine Fisheries Administration issued a rule permitting the use of SURTASS LFA, but it was blocked in court. It is now used only in limited areas of the Pacific for training.
"I feel it doesn't help to attack the Navy," Payne said. "They are actually doing their best to learn about these problems and do something about them. If we attack them too hard, we'll just get bizarre behavior."
Ventresca said the Navy actually is one of the largest funders of marine mammal research, providing 50 percent of all funds to examine the impact of human-generated sounds on the animals.
Not that such research needs to uncover basic answers. Th e effects of noise on animals can be dramatic. In severe test conditions, mice undergo audiogenic seizures, which is a nice way of saying they die from excessive noise.
Payne said early in his career he saw what appeared to be an audiogenic seizure by a wounded young whale that was being circled by a noisy boat.
The natural audio environment of the ocean is particularly rich and surprising - if you're a whale. Payne and fellow researcher Scott McVay discovered humpback whales produce "long complicated rigamaroles" that repeat every 10 minutes.
"They sing songs, which my former wife discovered were in fact changed by the whales over time," Payne said. "That's very unusual. Humpback whales make these wild arias, which are changed totally over a period of five years. These sounds are built according to many of the same rules that human composers use to compose our songs."
Blue Planet is a weekly series examining the relationship of humans to the environment, by veteran environmental reporter Dan Whipple.
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