Why the ocean is getting louder

We often think of the ocean as a totally silent place, muffled under the water’s surface and full of animals that don’t make a lot of noise. But that’s not really the case. For many marine species, sound functions as a primary sense, and plays an essential role in communication and finding food. For them, sound is as essential as sight is to humans.

But it’s getting harder and harder for those animals to hear anything in their native habitats. Ship traffic noise has doubled every decade since the 1960s, and it’s wreaking havoc on marine life. Whales and dolphins are struggling to hear each other over the low-frequency din of boat traffic. Researchers even analyzed whale poop to find that boats had a significant impact on North Atlantic right whale stress levels.

The most jarring interruption of the ocean soundscape comes from a process called seismic surveying. It’s an oil and gas exploration technique that involves firing high-powered airguns in the water to map out the ocean floor. It’s a loud process, with each blast usually clocking in at 120 dB. Christopher Clark, an expert in marine bioacoustics at Cornell University, compares the sound to “an explosion that is rattling grandma’s china out of the cupboard, and it is falling on the floor” — every 10 seconds.

The effects on ocean life have proven to be dramatic. Fish populations flee reefs during seismic testing, with numbers dropping by 78 percent. New research found that zooplankton died at two to three times the normal rate when seismic blasts occurred in an area, and baby krill were almost always completely wiped out.

Learn more about what louder oceans mean for marine life in the video above, made in collaboration with Twenty Thousand Hertz, a podcast all about sound. Listen to the podcast version of this story and subscribe here.