Snapping Shrimp's Cracking Sound May Impact Reef Ecology

Snapping shrimp may tell researchers a bit more about reefs. Scientists have found that the tiny snapping shrimp's noisy habits could play a big role in reef ecology.

Snapping shrimp are primarily found in reef environments, such as coral reefs and oyster reefs. Only one or two inches in length, the shrimp lives on the ocean floor and makes its signature sound by rapidly closing the larger of its two asymmetrical claws. In fact, these shrimp can snap their claws at a speed of about 60 miles per hour. When they do, a giant cavitation, or air bubble, forms. Water then rushes back into the air bubble and generates powerful energy that provides the shrimp both a weapon and a loud snapping noise.

In this latest study, the researchers looked at patterns in oyster reef sounds, because they believe that the natural background noise of the reef may play a role in helping organisms find the reef.

"We're not the only ones interested in reef sounds," said Del Bohnenstiehl, one of the researchers, in a news release. "But until now no one had sound samples from more than a couple of days or weeks at a time. If we're really going to explore the effects of sound on reef habitats and what that means, we need a longer sample."

In this case, the researchers took an entire year's worth of sound samples from the oyster reef in the Pamlico Sound. They found that there were seasonal differences in the level of sound, as well as differences between night and day.

"The overall impact in terms of noise emanating from the reef is a difference of 15 decibels between seasons," said Bohnenstiehl. "We also found that the shrimp were more active at night during the summer, but more active during the daytime throughout the winter months."

The findings reveal a bit more about sound, and how it might impact reefs.

"The data raises a lot of questions," said Bohnenstiehl. "For instance, some research has proposed that the noise of the reef helps migrating fish navigate. But if the sound really drops off in the winter, does this still work? And could the difference in snap numbers between the summers be affected by water quality as well as temperature? This work highlights how little we know, and how important long-term acoustic sampling is in terms of understanding the marine soundscape."

The findings are published in the journal PLOS One.

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