Polluting Our Oceans With Sound

By RJ Winberg

Our oceans were once referred to as "The Silent World" by Jacques Cousteau. However, since the industrial revolution, the ocean environment today has become increasingly noisy. In fact, the ambient noise in the ocean increased by an estimated 10 decibels (10 times louder) between 1950 and 1975, thus creating noise pollution.

Why is noise in the ocean a problem?

As the ocean becomes louder it makes life more difficult, more dangerous, and even deadly for the marine animals that inhabit it.  There are several reasons for this, but the first thing we should understand is that noise pollution in the ocean is very different than noise pollution on land.

The fact is that sound travels further in water. This means that loud sounds can travel great distances through the water and affect animals, hundreds or even thousands of miles away.

Additionally, many marine animals rely on sound to orient themselves both in their environment and within their community. Pods of dolphins, for example, use sound to communicate with one another. So when there is too much noise pollution it can significantly hamper marine animals' ability to communicate.

It has been found that Right Whales lose 50-70% of their opportunities to communicate when traveling through Cape Cod on the run-up to Boston Harbor. The problem is that the noise builds up to a point where the animals can no longer hear each other, or as Marine Scientist Christopher Clark explains it, "It’s the cellphone story, you know, ‘Can you here me now? Can you hear me now?’ But then, shortly thereafter, when the noise level goes beyond a certain threshold, the counter-calling, the chitchat between right whales, for example, just stops — they just give up. When the noise decreases, they start up again."

There are severe consequences when whales lose the ability to communicate. If a female cannot hear the mating call of males, they lose the opportunity to breed. If a whale cannot hear it's friends calling out the location for food, they lose an opportunity to eat.

What Causes Noise pollution?

When it comes to noise pollution, we can pretty much sum it up into two varieties: chronic and dynamic.

The first type of noise pollution is chronic and consistent. This primarily comes from ships driving through the water. The sound of motors turning, machinery rattling the hulls of the ships, and propellers spinning in the water sends vibrations through the water. As the scale of international shipping has increased over the decades a crescendo of constant noise in the ocean has come with it. Scientists believe that the underwater noise from ship traffic has been doubling approximately every 10 years. As learned from the Cape Cod example, this type of noise pollution can significantly dampen the ability of animals to communicate with one another, and thus exposes them to potential dangers.

The dynamic type, rather than being a steady hum of sound, has a more on-again off-again occurrence. This is actually much more harmful to marine life as it includes sounds that are louder than chronic noise pollution by several magnitudes, such as military sonar and underwater oil exploration.

In March of 2000, it was discovered that 17 whales had beached themselves in the Bahamas and that the entire population of beached whales had disappeared in the region. A federal investigation found sonar testing by the Navy to be the cause. An article by the Natural Resources Defense Council notes, "More than a dozen harbor porpoises were found dead on the beach near the San Juan Islands soon after the Navy tested active sonar in the Haro Strait in May. Videotape shows a pod of orca whales in the foreground behaving erratically as the Shoup, a U.S. Navy vessel, emits loud sonar blasts. Recent tests on one of the harbor porpoises revealed injuries consistent with acoustic trauma."

There have been many cases throughout the years where whales have been found with severe ear injuries caused by sonar. However, the U.S. government has since passed legislation that limits the frequencies at which sonar can operate in an effort to prevent these kinds of injuries to marine wildlife.

Underwater Oil Exploration.

The Obama Administration recently reversed a decision to allow oil exploration off of the U.S. East Coast. However, oil companies are still allowed to conduct Exploratory Seismic Air Gun Surveys to look for areas rich in oil or natural gas.

They typically deploy 30-40 air guns that all go off simultaneously every 9-12 seconds. These air guns produce pressure bubbles that contract and expand sending out immense levels of acoustic energy. As the ships travel back and forth over large areas of the ocean, the sound waves bounce off the earth's crust and return to the boats. They then use this data to determine where they have the best chance at discovering fossil fuel.

These blasts of sound are usually 6-7 times louder than the loudest ships.  "It is so loud that when someone is surveying off northern Brazil, I can hear that explosion on a small piece of instrumentation that I deploy 60 miles off the coast of Virginia. I can hear the explosions from surveys off Ireland, I can hear them happening in Nova Scotia." Clark continues.

So what can we do about it?

We can do better, by making use of amazing technologies that are already available to us. There are research ships out there that are 1,000 times quieter than previous ships. The Vibroseis is an alternative to air guns that makes use of carefully designed sweeps of sound that are orders of magnitude quieter and just as effective.  The tools are already out there, we just need the social and political will to implement them. 

Research what corporations, government agencies, and scientists are doing to extract resources. Educate yourself and your family and become knowledgeable about noise pollution.