California Coast & Ocean

A Cacophony
Jacques Cousteau’s characterization of the ocean as “the silent world” was more poetic than accurate: the undersea realm is actually a noisy place. Waves, wind, rain, lightning strikes, earthquakes, and other natural processes produce sounds underwater. Dolphins make clicking noises to help them navigate and find food, whales and seals sing, and colonies of snapping shrimp can be so loud that they drown out sonar. Even some types of fish make noise. The oyster toadfish, for example, produces a sound similar to a foghorn by contracting the muscles of its swim bladder.

Sound is a vital sense for creatures that live in the ocean. It travels much faster, and potentially much farther, through water than it does through air, while vision, smell, touch, and taste are impeded. Marine animals have evolved not only to take advantage of the special properties of sound in water, but also to accommodate the cacophony of the ocean’s natural sounds.

In the past several decades, human activities have been generating ever more mechanical and technological noise in the underwater world. Sonar noise has come to public attention, but there is much more: seismic airguns used to search for oil and gas, drilling, explosives, underwater construction, and shipping all add to the din, particularly in coastal waters. Two studies conducted in the mid-1990s to early 2000s along the California coast--one off San Nicolas Island, the most remote of the Channel Islands, and one off Point Sur--found that underwater noise at low frequencies had increased by about 10 decibels since the Navy made sound recordings in the same areas in the mid-1960s. That means that the sounds may be more than twice as loud to some marine animals as they were then, according to Southall. Both studies suggested that steep increases in international shipping traffic and gross tonnage might explain the rise in sound volume in ocean waters.

“Underwater ambient noise has just about doubled every decade since World War II, and by far and away the biggest increase has been in shipping noise,” said Richard Steiner, a professor and marine conservation specialist with the University of Alaska’s Marine Advisory Program. “There are about three times as many ships as there were 50 years ago, and seven times the gross tonnage.”

Although it is difficult to determine how many commercial ships ply the oceans at any one time, Lloyd’s Register of Shipping put the world’s commercial fleet (which includes cargo and cruise ships, tankers, dredges, tugs, and fishing boats) at approximately 91,000 as of 2006, according to the Colton Company, maritime consultants. In California, the number of container units moving through the ports of Los Angeles and Long Beach nearly tripled during the past decade, increasing from 5.8 million in 1996 to 15.8 million in 2006. Both ports estimate that current numbers could double or triple in the next 15 to 20 years. A new port has been proposed near Ensenada in Baja California, in part to serve as an alternative to busy L.A. and Long Beach.

A 2003 report by the National Academies, “Ocean Noise and Marine Mammals,” stated that “vessel traffic is a major contributor to noise in the world’s oceans,” especially at low frequencies, and that distant traffic contributes significantly to background noise. “Very large geographic areas are affected,” the report noted. Some studies have found that vessel noise can be heard as far as 1,000 miles from its source.

“Underwater noise from shipping is the most pervasive unregulated pollutant on earth,” said Steiner. It’s likely to become even more pervasive, especially in the Pacific Basin, with global trade booming and more and ever bigger commercial ships traveling between Asia and the United States.