Ocean scientists assess impact of seismic pulses in effort to prot...( WASHINGTON - Scientists investigating t...)

WASHINGTON - Scientists investigating the possible effect of underwater seismic pulses on marine mammals have conducted a series of tests, designed to better understand the force of sound waves generated by shipboard airguns. These instruments are used by some 100 vessels worldwide to penetrate into the seabed for oil exploration and geophysical research, with an estimated 15 to 20 active on any given day.

Researchers from the Lamont-Doherty Earth Observatory of Columbia University conducted tests in the northern Gulf of Mexico in 2003, using the 20-gun array aboard their research vessel, Maurice Ewing. Their results will be published July 27 in Geophysical Research Letters (GRL), a journal of the American Geophysical Union. While most other scientific research ships can only deploy much smaller systems, Maurice Ewing's 20-gun capacity is comparable to those aboard many industry ships. It provides the flexibility to design source arrays of many different sizes and power, allowing scientists to look deep below the ocean's surface to study problems as diverse as earthquake prediction and the ocean's role in the carbon cycle.

Maya Tolstoy, lead author of the study, writes that the researchers covered sound frequencies of concern to many species of marine mammals. The GRL paper focuses in part on beaked whales, a relatively little known family of 18 species found, often at great depths, in all of the world's oceans.

Only one event of stranding of beaked whales that might be related to airgun activity has been recorded, Tolstoy writes, but there is solid evidence that some other species of whales avoid the acoustic output of seismic systems at distances up to 20 kilometers [10 miles]. In 2002, two beaked whales were stranded in the Gulf of California at around the time R/V Maurice Ewing was conducting acoustic research in the area, but a causal relationship has not been established. Some beaked whale strandings have occurred in connection with Nav
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Contact: Harvey Leifert
hleifert@agu.org
202-777-7507
American Geophysical Union
26-Jul-2004

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