The sea is lovely, dark and deep — but it’s not quiet. In recent decades, the explosive growth of manmade noise from ships, sonar activity and oil drilling has created a new class of worries for marine animals and the scientists who study them. In the United States, researchers and activists are renewing a long-stated concern that the noise from oil exploration may be too much to bear for the last remaining North Atlantic right whales.
In a few months, the U.S. Atlantic coast may get another layer in its cacophony of ocean noise: the dynamite-like blasts of seismic airguns, which are used to search for oil and gas deposits buried beneath the seabed. In April, 28 right whale scientists warned President Obama that seismic airgun blasting will come at a high cost to whales’ ability to eat, rest, communicate and reproduce. With only 500 North Atlantic right whales (Eubalaena glacialis) left alive, this may “substantially increase” the risk of extinction.
Ships can tow dozens of seismic airguns behind them during a survey, each airgun emitting bursts of sound every 10 to 12 seconds, up to 24 hours a day. These surveys can last anywhere from days to months. While the Obama administration put the East Coast off-limits to oil and gas drilling until 2022, seismic airgun blasting has not yet been shelved.
The government could approve permits for seismic airgun blasting in the Atlantic as early as this summer. And oil companies could deploy these devices immediately after receiving approval, said Ingrid Biedron, Ph.D., a marine scientist at Oceana.
One of the big concerns some biologists have is not just how loud these sounds are, but how far they can travel. Aaron Rice, Ph.D., an expert on bioacoustics at Cornell, explained that airgun noise can travel hundreds if not thousands of miles. “At our recording units off the coast of Virginia, we may be picking up seismic surveys off the coast of Brazil,” he said. In today’s world, “there are very few, if any, truly quiet locations around the planet.”
Biedron explained what life on the Atlantic coast sounds like for a right whale. “There’s a constant din of noise, and that’s on a good day,” she said. “On a bad day it’s probably more like a barrage of sound and ships, clickers and radar. It’s like having a rock concert in your back yard for the rest of your life.”
Can You Hear Me Now?
Like people, right whales are a talkative lot. And, like us, right whales need to hear and be heard. Their most common vocalization, the lilting up-call, is the cetacean equivalent of saying “I’m over here.” These calls are so common, in fact, that a series of buoys equipped with microphones north of Cape Cod listen for up-calls to alert ships when right whales are nearby.
Females likely use these calls to alert males when they’re in a romantic mood, or to summon wandering calves back to safety. Areas under consideration for seismic airgun blasting overlap with the only known calving ground for this species.
Sound may play other, more exotic roles in right whale life. Scientists still need to confirm these ideas, Biedron cautions. But some researchers think that right whales can listen for the different sounds that come from land and use it to navigate. Others suspect that North Atlantic right whales may use a variation of their up-call to tell neighbors when they find plankton — an altruistic strategy that animals could adopt when food is abundant but unpredictably distributed. However, the deep rumble of ships or the blasts of seismic airguns can drown out these calls.
Manmade noise likely hurts whales in physical ways too. According to Rice, dozens of studies across different species of vertebrates confirm that noise increases stress hormones, which in turn suppress the immune system. “If you’re really stressed out,” he said, “you’re more likely to get sick.”
Ship strikes and getting tangled in fishing gear remain the leading cause of death for North Atlantic right whales. But, “in the case of the right whale, it may be death by a thousand cuts, of which sound pollution is one of those cuts,” said Rice. “Sound plus entanglements, or sound plus ship strikes, may be more problematic than either of those two threats on their own.”
Now, despite decades of protection, the prognosis for these whales is still grim. Their numbers grew slowly from the 1990s to 2010, but there are signs that they may once again be on the decline. “The population is so precarious” Biedron said, “that even the loss of just several females per year could make them tip towards extinction.”
Government and industry officials have taken steps to cut down on underwater noise pollution, including developing new alternatives to seismic airguns, “quieting” ship engines, and considering regulations that limit the volume from commercial ships. But current efforts aren’t enough.
Rice expressed little hope for the future of the North Atlantic right whale. But a promising sign, he added, is that noise pollution is beginning to get the attention it deserves in the European Union, Canada and increasingly, the U.S. Biedron had a less gloomy outlook. “I’m optimistic,” she said. “But we need to remain vigilant. If we stop paying attention, they will likely go extinct.”