Evidence of a drop in underwater noise pollution leads experts to predict the Coronavirus crisis may be good news for whales and other sea mammals
Curtailing of shipping due to coronavirus is now allowing scientists to study the effects of quieter oceans on marine wildlife.
There has been a consistent drop in noise since 1 January, which has amounted to a change of four or five decibels in the period up to 1 April
David Barclay, assistant professor of oceanography at Dalhousie University
Researchers examining real-time underwater sound signals from seabed observatories found a significant drop in low-frequency sound associated with ships.
The work is run by Ocean Networks Canada, who operate ocean observatories to collect data on physical, chemical, biological and geological aspects of the ocean over long time periods.
Following the terrorist attacks of 9/11, when ship and air traffic fell in North America, US researchers were similarly able to study whales in a quieter ocean, with a landmark study concluding that ship noise was associated with chronic stress in baleen whales.
“We have a generation of humpbacks that have never known a quiet ocean,” said Michelle Fournet, a marine acoustician at Cornell University, who studies humpback whales in south-east Alaska and whose work has shown that the whales alter their calling behaviour in response to a noisy ocean.
“What we know about whales in south-east Alaska is that when it gets noisy they call less, and when boats go by they call less,” said Fournet.
Image: Juergen Ritterbach/Alamy
Nathan Merchant, a bioacoustics expert at the UK government’s Centre for Environment, Fisheries and Aquaculture Science (Cefas), said there have been international efforts to coordinate the work of monitoring underwater noise.
“We will be looking at how the coronavirus is affecting underwater noise throughout Europe, so this work … will be the first of many,” he said.
Merchant and his colleagues have long been discussing how they could ever conduct an experiment to make the ocean quieter, in order to find out what benefit it would have.
10 facts about sound in the ocean…
- Sound waves travel much farther in the ocean than they do in air. Marine mammals, fish, and other species have evolved to depend on hearing as their primary sense, for whales this can be across huge distances.
2. Researchers who made a sound in the Indian Ocean were able to detect it in both Washington State and in the Atlantic Ocean.
3. A single container ship can put 190 decibels of sound energy in the water, louder than standing next to a speaker at a rock concert.
4. Roughly 60,000 tanker and container ships ply the seas at any given time. This underwater cacophony creates a kind of ‘smog’ that reaches nearly every corner of the ocean and shrinks the sensory range of marine wildlife.
5. Right whales, an endangered species living in the North Atlantic, can no longer hear each other as much as 80% of the time. It’s a relatively recent change; since some whales can live 200 years, some of them grew up in a quiet ocean.
6. Noise pollution generated by shipping and military activity can cause cellular damage to invertebrates like jellyfish and anemones. These animals are a vital food source for tuna, sharks, sea turtles and other creatures.
7. High-intensity sonar used by the military has been linked to mass whale strandings.
8. Scans of 17 stranded beaked whales showed evidence of haemorrhaging around the brain, and blood around the ears. Extreme noise – sonar tests from Navy warships had driven the whales to try to get out of the water.
9. In the hunt for offshore oil and gas, high-powered air guns fire compressed air into the water every 10 to 12 seconds from weeks to months. Travelling as far as 2,500 miles, these deafening seismic blasts disrupt foraging, mating, and other vital behaviours of whales.
8. Over the last 50 years, as cargo shipping and deep sea oil exploration has increased, background noise in the ocean has doubled roughly every decade.
What is being done about ocean noise?
Better technology can dramatically reduce the noise we’re making. Oil and gas drillers, for example, usually use airguns with massive dynamite-like explosions to map the sea floor. But it’s possible to use marine vibroseis, a technology that’s thousands of times less invasive.
This is a problem that can be solved. The only good thing about ocean noise pollution is that noise disappears once you stop making it–it doesn’t linger behind very long in the environment like other pervasive pollutants do
Michael Jasny, director of the Marine Mammal Protection Project at the Natural Resources Defense Council
In 2014, the International Maritime Organisation adopted voluntary guidelines for quieter ships. Some shipping companies are beginning to use quieter propellers which happen to be more efficient and save fuel.
Ships can also reduce noise just by slowing down. Since it’s typical to wait three days at a port after arrival, some experts argue that there’s no reason to go faster.