A group of people watch a turtle swim to the ocean after rehabilitation Tuesday in Jacksonville, Fla. The Obama Administration is opening the Eastern Seaboard to offshore oil exploration for the first time in decades. The announcement made Friday also approved the use of sonic cannons to map the ocean floor to identify new oil and gas deposits in federal waters from Florida to Delaware. The sonic cannons pose real dangers for whales, fish and sea turtles.

ST. AUGUSTINE BEACH, Fla. - The Obama administration is reopening the Eastern Seaboard to offshore oil and gas exploration, announcing final approval Friday of sonic cannons that can pinpoint energy deposits deep beneath the ocean floor.

The decision promises to create plenty of jobs and thrills the oil industry, but dismays environmentalists worried about the immediate impact as well as the long-term implications of oil development.

The cannons fill waters shared by whales and turtles with sound waves 100 times louder than a jet engine. Saving endangered species was the environmental groups' best hope of extending a ban against offshore drilling off the U.S. Atlantic coast.

The U.S. Bureau of Ocean Energy Management disclosed its final approval first to The Associated Press ahead of an announcement later Friday.

The approval opens the outer continental shelf from Delaware to Florida to exploration by energy companies preparing to apply for drilling leases in 2018, when current congressional limits are set to expire. The bureau is moving ahead despite acknowledging that thousands of sea creatures will be harmed.

"The bureau's decision reflects a carefully analyzed and balanced approach that will allow us to increase our understanding of potential offshore resources while protecting the human, marine, and coastal environments," acting BOEM Director Walter Cruickshank said in a statement.

These sonic cannons are already in use in the western Gulf of Mexico, off Alaska and other offshore oil operations around the world. They are towed behind boats, sending strong pulses of sound into the ocean every 10 seconds or so. The pulses reverberate beneath the sea floor and bounce back to the surface, where they are measured by hydrophones. Computers then translate the data into high resolution, three-dimensional images.

"It's like a sonogram of the Earth," said Andy Radford, a petroleum engineer at the American Petroleum Institute, an oil and gas trade association in Washington DC. "You can't see the oil and gas, but you can see the structures in the earth that might hold oil and gas."

The surveys can have other benefits, including mapping habitats for marine life, identifying solid undersea flooring for wind energy turbines, and locating spots where sand can be collected for beach restoration. But fossil fuel mostly funds this research, which produces data held as energy company secrets and disclosed only to the government.

"They paid for it, so I can see why they don't want to share. These things are not cheap," said John Jaeger, a University of Florida geology professor.

The bureau estimates that 4.72 billion barrels of recoverable oil and 37.51 trillion cubic feet of recoverable natural gas lies beneath federal waters from Florida to Maine. Oil lobbyists say drilling for it could generate $195 billion in investment and spending between 2017 and 2035, creating thousands of jobs and contributing $23.5 billion per year to the economy.

These estimates describe the total amount of energy "technically recoverable" from the outer continental shelf, which includes the seabed off New Jersey, New York and New England. But the north Atlantic zone remains off limits for now, apparently for political reasons. While some states have passed drilling bans, Virginia and the Carolinas requested the seismic surveys in an effort to grow their economies, bureau officials said Friday.

In any case, the area to be mapped is farther offshore in federal waters, beyond the reach of state law.

The sonic cannons are often fired continually for weeks or months, and multiple mapping projects may operate simultaneously. To get permits, companies will need to have whale-spotting observers onboard and do undersea acoustic tests to avoid nearby species. Certain habitats will be closed during birthing or feeding seasons.

Still, underwater microphones have picked up blasts from these sonic cannons over distances of thousands of miles, and the constant banging -- amplified in water by orders of magnitude -- poses unavoidable dangers for marine life, scientists say.

Whales and dolphins depend on being able to hear their own much less powerful echolocation to feed, communicate and keep in touch with their family groups across hundreds of miles. Even fish and crabs navigate and communicate by sound, said Grant Gilmore, an expert on fish ecology in Vero Beach, Fla.

"We don't know what the physiological effects are. It could be permanent hearing damage in many of these creatures just by one encounter with a high-energy signal," Gilmore said.

More than 120,000 comments were sent to the government, which held hearings and spent years developing these rules. The bureau's environmental impact study estimates that more than 138,000 sea creatures could be harmed, including nine of the world's remaining 500 north Atlantic right whales.

These whales give birth and breed off the coast of Florida, Georgia and the Carolinas before migrating north each year. Many other species vital to East Coast fisheries also travel up and down the Gulf Stream.

"Once they can't hear -- and that's the risk that comes with seismic testing -- they are pretty much done for," said Katie Zimmerman, a spokeswoman for the South Carolina Coastal Conservation League based in Charleston, S.C.

"Even if there were oil out there, do we really want that? Do we really want to see these offshore rigs set up? Do we really want our tourism industry to suffer? Do we really want our environment to suffer?" she asked.

Some of these animals are so scarce that intense noise pollution could have long-term effects, agreed Scott Kraus, a right whale expert at the John H. Prescott Marine Laboratory in Boston. Scientists can't even approach them without extensive permits from federal marine mammal regulators.

"No one has been allowed to test anything like this on right whales," Kraus said of the seismic cannons. "(The Obama administration) has authorized a giant experiment on right whales that this country would never allow researchers to do."

Before the U.S. Atlantic seabed was closed to oil exploration in the 1980s, some exploratory wells were drilled, but the region has never had significant offshore production.

"One thing we find is, the more you get out and drill and explore to confirm what you see in the seismic -- you end up finding more oil and gas than what you think is out there when you started," Radford said.

Opposition to oil development has been abundant along the coast, where people worry that oil will displace fisheries and tourism. More than 16 communities from Florida to New Jersey passed resolutions opposing or raising concerns about the seismic testing and offshore drilling. Some states have passed

The local economy is fueled by beach tourism and fishing in St. Augustine in north Florida, where rare turtles come ashore to lay their eggs.

"Florida has already felt the devastating effects of an uncontrolled oil release with the Deepwater Horizon event of which cleanup efforts are still on-going," said John Morris, a county commissioner whose constituency includes St. Augustine Beach. "Any oil spill, large or small, off the coast of St. Johns County, would greatly affect the county's economy."