'Bubble curtains' could save marine life from deadly man-made underwater sounds

Okay, this isn't really an underwater treasure discovery story, but there's been a dearth of those lately so I thought I'd share this.

From Daily Mail Online: 'Bubble curtains' could save marine life from deadly man-made underwater sounds
Underwater noises from off-shore exploration and construction are capable of confusing and even killing marine life – but now scientists believe bubbles could save the day for denizens of the deep sea.

Researchers are developing ‘bubble curtains’, which spit millions of bubbles through the water and dampen damaging sound waves.

Development of this technology was spurred on by the deaths of dozens of fish that occurred during the retrofit of the San Francisco-Oakland Bay Bridge.

National Geographic reported that after 300-foot pilings were driven into the ocean dead fish appeared on the surface nearby, with tests afterwards showing that huge pressure waves from the drilling had compressed the air in the swim bladder, which then rapidly expanded, bursting the bladder and causing fatal kidney damage.

To lessen the impact of its activities, the firm behind the project, Caltrans, decided to deploy bubble curtains, which greatly lessened fish fatalities.

Californian marine biologist Bud Abbott, a consultant on the project, told National Geographic how the devices weaken sound waves.

He said: ‘When a pressure wave hits an air bubble, it will compress the bubble, then it will expand again, so energy is lost.

‘Sound travels faster through water than air. It slows down as it hits the air bubble.’

The devices won’t just save the lives of marine animals, but also make life for them much less confusing and stressful.

Many marine mammals find food and mates using sound pulses, which undersea noises interfere with.

While researchers from the New England Aquarium in Boston have shown that noises from ships' propellers actually increase stress-hormone levels in whales.

One company under scrutiny over its noisy underwater activities is Shell, with the U.S. National Oceanic and Atmospheric Administration (NOAA) revealing that one of its proposed Arctic seismic surveys would bring sounds of over 160 decibels to a 74-square-mile area.

This is a level researchers believe could dramatically affect marine life. By comparison, sounds of 130 decibels would be painful to humans.

However, Shell says that it is taking this issue seriously and is developing its own bubble curtain devices.

Mitch Winkler, manager of the Arctic Technology Program at Shell International Exploration and Production, told National Geographic that ‘marine sound is important’.

He added: ‘We are focusing on the use of air bubbles and their impact on sound waves as a means of reducing the sound transmitted from stationary sources.’