Oceanic Noise Pollution

Causes of Oceanic Noise Pollution Usually when people think of pollution they conjure up images of sewage spilling into the oceans, massive oil spills, floating trash and maybe even toxic chemicals. Noise pollution, however, is easily left out of such thoughts. Nevertheless, pollution from noise is likely as dangerous to many marine animals as any other type of pollution.

Historical Marine Noise Pollution Historically, ambient ocean noise levels were low enough that whales using sonar were able to communicate with each other across entire ocean basins. Recently though, increased underwater noise pollution has made communication between whales more difficult than ever. Without the use of sonar many cetacean species are unable to hunt for food, find mates or communicate with each other. Scientists estimate that ambient ocean noise increased ten decibels (one order of magnitude) from 1950 to 1975. It is only in the last 150 years that humans have caused major noise pollution. High intensity sound in the oceans may not dissipate for thousands of miles. Humpback whales, pictured below, are particularly sensitive to oceanic noise pollution.

Sources of Marine Noise Pollution Unfortunately for many marine species, boat traffic creates incredibly loud noises. Many of these loud signals are below the margin of 1000Hz. Modern day supertankers cruise the oceans creating a sound pulse of 190 decibels or more at or below the 500Hz range. Smaller boats such as tugs and ferries typically create a sound wave of 160-170 decibels. These ships create a virtual wall of "white noise" that has a constant loudness. This white noise can block communication attempts between cetaceans or limit them to very small areas.

These Stellar sea lions and California sea lions use sonar to echo-locate in the water and to communicate with each other. Underwater noise pollution makes it harder for these amazing animals to find food and communicate. Other species such as Gray Whales also use sound for similar purposes and suffer the same problems. Sound pollution sometimes even causes Gray Whales to break away from their normal migration routes.

The pictures above indicate some of the sources of underwater noise.

On land animals and humans alike know to move away from a loud or traumatic sound; the further we get, the more the sound dissipates. Underwater, we would not be so lucky. Sonar and ship noise can send a deafening tidal wave of noise for miles. It is difficult to pinpoint the origin or source of a particular sound and even harder to avoid or outrun it. Whales, dolphins and other marine mammals that have been caught in the wake of sonar have died of cerebral hemorrhaging or intentionally beached themselves in a desperate attempt to avoid the ear-splitting resonance.

Dr. Sylvia Earle, oceanographer, marine botanist, ecologist, writer, and former Chief Scientist at the United States National Oceanic & Atmospheric Administration (NOAA), summarizes the problem of noise pollution. "Undersea noise pollution is like the death of a thousand cuts. Each sound in itself may not be a matter of critical concern, but taken all together, the noise from shipping, seismic surveys, and military activity is creating a totally different environment than existed even 50 years ago. That high level of noise is bound to have a hard, sweeping impact on life in the sea." Regulating these sound sources can be difficult but one has to start somewhere. Unless we really understand how that vast system works and take better care, it isn’t just the ocean that’s in jeopardy

Underwater, as on land, we must do better to protect those resources we share. Most of us cannot imagine the violent intrusion created by a shipping barge passing overhead. Notwithstanding the need for compassion, with this new knowledge of sound in the underwater environment comes the responsibility to protect those animals and fish and creatures that cannot protect themselves. We have the intellect and the technology to develop better boats and better defense tactics that will enable us to be better stewards of the ocean environment.

Racheva Alexandra 11-A