Animals that live in the ocean communicate with sound — humpback whales, for example. But these voices could soon be drowned out by powerful sonic booms from vessels searching for oil and gas.
President Trump is opening up the Atlantic Coast to companies to explore for fresh reserves. And to explore, they will be making some of the loudest sounds ever heard in the ocean — sounds that, according to recent research, could harm marine animals from whales to plankton.
Five companies are currently applying for permits to use seismic air guns to survey thousands of miles of the seabed along the Atlantic Coast. If they get the permits, they could start later this year.
The air guns are devices towed behind a ship. They compress and then release air explosively, and the sound waves penetrate the seabed. When they bounce back to receivers, also towed from the ships, the sound waves paint a picture of reservoirs of oil and gas beneath the seabed.
The sound blasts can also damage the ears and internal organs of marine animals. Ships will have to turn them off if they see whales or other marine mammals nearby.
But there's growing evidence that these sounds may seriously affect animals swimming well outside the immediate danger zone. Aaron Thode is an oceanographer who's studied the subject and advises the Marine Mammal Commission, a federal agency that regulates activities affecting marine life.
"We don't know what happens if animals are exposed constantly to sound over long periods of time in, say, a feeding area or a breeding area or what not," Thode explains.
Thode works at the Scripps Institution of Oceanography. He says whales have been observed retreating from the sound of air guns. That could cause them to abandon breeding or feeding grounds.
Thode's own research has shown that bowhead whales start calling more often to each other when there's air gun noise, at least for a while. "At some point, you know, just as if a jet plane passes overhead, you just give up and wait for the sound to decrease," Thode says.
If the whales go silent, that not only has potential effects on their communication, but also on air gun surveyors. Federal rules require them to listen to for whale sounds and, if they hear them, to stop their air gun blasts. But if the whales aren't making noise, their presence underwater won't be known unless they're sighted at the surface.
Scientists believe that air gun sounds could "mask" communication by marine animals. Surveyors will be blasting several times a minute, for months at a time. Marine biologist Doug Nowacek at Duke University worries that that kind of constant noise could cause a mother, for example, to lose track of its calf. "If they get separated by a few tens or hundreds of meters in an increasingly loud ocean," he says, "you can consider it gone."
Nowacek says recent scientific evidence suggests that these more subtle effects of air guns could extend a long way. "The levels that could still have and do have behavioral impacts extend out tens, and hundreds of miles away from those surveys," he says.
And effects on smaller animals are emerging as well. Research in Australia shows that nearby air guns can actually kill shrimp-like plankton and their larvae. Even scallops have been observed recoiling from air gun sound.
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