Oh, Snap! Hear the Big Noise Tiny Shrimp Make in the Ocean

Snapping shrimp in petri dishes. (Courtesy Woods Hole Oceanographic Institution)

You may think it’s quiet in the ocean, but a tiny creature is raising quite a ruckus as ocean temperatures rise. New research presented at this year’s Ocean Sciences Meeting in San Diego says the oceans may be getting louder.

And that's because of shrimp.

The ocean’s acoustic environment has been drawing a lot of attention as scientists learn that many of its inhabitants use sound to communicate. Whale songs and dolphin squeals have captivated audiences of nature documentaries and animated films, but fish and invertebrates also signal one another with sound in the ocean waters.

Snapping shrimp — over 300 species of them — live in coastal oceans all around the world. These shrimp may be some of the smallest critters in coral reefs, and they’re also some of the loudest. Generally less than an inch long, these tiny crustaceans snap their claws fast to create air bubbles that implode with a pop! With these sounds, snapping shrimp communicate with each other and defend their territory. The combined snaps from shrimp colonies create a cacophony that divers and submarine crews can easily hear. You can hear the sound, which is reminiscent of spattering rain or fying bacon, by clicking here or on the audio link at the top of the article.

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Pumping Up the Volume in Warmer Water

At the Woods Hole Oceanographic Institute in Massachusetts, marine biologists Aran Mooney and Ashlee Lillis have studied snapping shrimp on coral reefs in the Atlantic Ocean and in the lab. They’ve examined how shrimp, individually and in groups, change their tune at different temperatures.

“We found, both in terms of observing the coral reefs and with animals in the lab, that if you increase temperature in the water, these snapping shrimp have increased their snap rates and the oceans actually get louder,” Mooney said.

That’s likely because these animals become more active in warmer water. The heat likely increases their need to communicate with each other.

Mooney’s experiments showed that changing the temperature from 70 to 85 degrees Fahrenheit nearly doubled the snap rate. As the temperature increased by one degree Celsius, the noise level rose by 1-2 decibels.

That pumps up the volume for other marine animals, said Annebelle Kok, a marine ecologist at Scripps Institution of Oceanography in San Diego. “I was very impressed by this work,” she said, noting the originality and creativity of the researchers’ approach to studying warming oceans.

As ocean temperatures continue to rise, Mooney said, the shrimp symphony could cause problems for other communications under the sea. “We know that fish hear, but we really don't understand that for most species of fish, especially really important commercial species of fish,” he said. “And so increasing this level of noise … we really don't understand how that would impact these fish.”

Other species also rely on underwater sound to gather information, as do commercial fishermen and the U.S. Navy, which use sonar equipment that the constant background noise from chattering shrimp could interrupt.

Noisier oceans could also cause problems for marine biologists. “If this really is a wider pattern and the oceans continue to warm,” Kok said, “then that might mean that it will be more difficult for people to extract other sounds from the soundscape, such as dolphin sounds."

“It's too early to say if this applies to other parts of the ocean,” Kok said. She's looking forward to reviewing further research.