Could Listening to the Deep Sea Help Save It?

You might know what a hydrothermal vent looks like: black plumes billowing from deep-sea pillars encrusted with hobnobbing tubeworms, hairy crabs, pouting fish. But do you know what a hydrothermal vent sounds like?

To the untrained ear, a hydrothermal vent — or more precisely, one vent from the Suiyo Seamount southeast of Japan — generates a viscous, muffled burbling that recalls an ominous pool of magma or a simmering pot of soup.

To the trained ear, the Suiyo vent sounds like many things. When asked during a Zoom call to describe the Suiyo recording more scientifically, Tzu-Hao Lin, a research fellow at the Biodiversity Research Center at Academia Sinica in Taipei, Taiwan, took a long pause, shrugged, and laughed. People always ask him this, but he never has the answer they want to hear. “I usually tell people to describe it with their own language,” Dr. Lin said. “You don’t need to be an expert to say what it sounds like to you.”

Dr. Lin adores acoustics; in his official academic headshot, he wears a set of headphones. He has listened to the sea since 2008, and to the deep sea since 2018. He has deployed hydrophones, which are microphones designed for underwater use, in waters off Japan to eavesdrop on the noises that lurk thousands of feet below the surface. He published these recordings in August at a conference of the Deep-Sea Biology Society.

Dr. Lin is not interested in focusing on the song of a singular whale or the clatter of ship traffic, but rather on the habitat’s soundscape — the totality of all its sounds, human, animal and geological — to glean an area’s biodiversity. Think of it as a hydrothermal vent’s acoustical calling card.

Dr. Lin joins a growing field of acousticians who believe that sound may be the quickest, cheapest way to monitor one of the most mysterious realms of the ocean. A database of deep-sea soundscapes could provide researchers with baseline understanding of healthy remote ecosystems, and singling out the sounds of communities or even individual species can inform scientists when populations are booming.

“You need to know what the habitat sounds like when it’s healthy,” said Chong Chen, a deep-sea biologist at Japan Agency for Marine-Earth Science and Technology, or JAMSTEC. “When the soundscape has changed, the habitat may have changed, too.”

The allure of deep-sea sound

Light holds little power in the ocean; it is so easily absorbed and scattered by seawater that anything deeper than 656 feet is essentially shrouded in darkness. But sound reigns supreme underwater, where it travels five times faster than in air.

If this statistic seems abstract, several acousticians laid out a helpful scenario in a 2018 paper in Acoustics Today. Imagine staring down at a city on a clear day from atop a mountain, the highest point within 60 miles. You can see far into the horizon but only hear the sounds nearby, perhaps a chirping bird or a gust of wind.

In the deep sea, the rules are reversed. Standing on a ridge several thousand feet underwater, peering out to the ocean’s abyssal plain, you would see almost nothing. But if you listened through a hydrophone, you could detect sounds from…