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Noises Off

Whales and dolphins win protections against seismic survey blasts.

 

Whales, dolphins and other denizens of the Gulf of Mexico’s underwater world use sound to communicate with one another, find food and perform other critical activities. One intrusion on that world has been seismic survey noise, a byproduct of oil and gas drilling. Relief is at hand, however, as the oil and gas industry has agreed to protect sea creatures from the worst impacts of that noise.

The landmark agreement was reached last summer in response to a lawsuit filed by four environmental groups.

The noisiest part of oil development occurs during a seismic survey, when arrays of airguns go off for extended periods of time. Scientific studies have found that the explosive noise from surveys can disrupt whale behaviors. As the blasts reverberate off the ocean floor and spread outward, they create a blanket of noise that makes it harder for whales to hear each other calling.

“The ocean is an acoustic world,” says Michael Jasny, director of the Natural Resources Defense Council’s Marine Mammal Protection Project. “Whales and dolphins and fish have evolved over millions of years to rely on sound to find mates, avoid predators, find food and maintain bonds.”

Gus Engeling deer

Limits on seismic surveys are making Gulf waters a quieter place for whales and dolphins. The surveys use airguns when prospecting for oil and gas.

The agreement is bringing relief for the Gulf’s more than 20 species of whales and dolphins. It puts biologically critical areas off-limits to surveying — for example, in bottlenose dolphin habitat in March and April, during peak calving season. It halts prospecting year-round in the DeSoto Canyon, a nutrient-rich area near the mouth of the Mississippi River that is a favorite spot for sperm whales and home to the fewer than 50 Bryde’s whales. And it puts new safeguards in place throughout the Gulf, requiring surveys to be more widely spaced and to avoid unnecessary duplication. The limits are in effect for 2 1⁄2 years.

In recent years, marine mammal observers have been posted on the decks of survey ships to make sure sperm whales aren’t in the area before starting a survey; now they are required to use underwater microphones during times of reduced visibility.

Additionally, the industry is developing an alternative technique called marine vibroseis, which is quieter than airguns. This technology vibrates the water instead of sending shock waves and can be fine-tuned to the needed bandwidth. As a result, it eliminates waste noise and limits the sound produced to a level that is below the audible range of most of the Gulf’s whales and dolphins. Just as airguns replaced dynamite in the early 1960s because it was harmful to humans and fish, this new technology will help make oil exploration safer for marine mammals.

This development comes at a critical time. Another oil and gas boom is underway in the Gulf, which, with its more than 3,000 platforms, is “probably the most prospected body of water on the planet,” according to Jasny. After a six-month moratorium triggered by the Deepwater Horizon disaster, permitting is now at a record high. In December, Congress opened a new 1.5 million acres to drilling when it passed legislation to develop boundary waters jointly with Mexico. The next frontier for new platforms is in deeper waters of up to 5,000 feet, where sperm whales live.

Newcomers are moving into the neighborhood, but at least they’ve agreed to keep down the noise.

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