, University of California, Santa Cruz; Kathleen Vigness-Raposa , Marine Acoustics, Inc.
The deep is dark, but not silent; it’s alive with sounds. Whales and other marine mammals, fish, and even some invertebrates depend on sound, which travels much farther in water than light does. The animals use sound to find food and mates, to avoid predators, and to communicate. They face a growing problem: Man-made noise is drowning them out. “For many of these animals it’s as if they live in cities,” says marine scientist Brandon Southall, former director of the National Oceanic and Atmospheric Administration’s (NOAA) ocean acoustics program.
Two years ago the problem made it to the U.S. Supreme Court, in a case that might have been called U.S. Navy v. Whales. The Court’s decision protected the right of naval vessels to test submarine-hunting sonar systems, whose intense sound pulses have been linked to several mass whale strandings. But the Navy is not the lone villain. Oil company ships towing arrays of air guns fire round-the-clock fusillades loud enough to locate oil buried under the seafloor—and also to be heard hundreds of miles away. Undersea construction operations drive piles into the seafloor and blast holes in it with explosives.
And most of the rising tide of noise—a hundredfold increase since 1960, in many areas—is created simply by the dramatic growth in shipping traffic. “Shipping noise is always there,” Southall says. “It doesn’t have to be lethal to be problematic over time.” The problem is getting steadily worse for another reason. As we’re making more noise, we’re also making the ocean better at transmitting it. Seawater is absorbing less sound as carbon dioxide from fossil-fuel burning seeps into the ocean and acidifies it.