Warming oceans are causing shrimp to snap louder. Here's why that's a problem

In a first study of its kind, WHOI scientists have established a clear relationship between rising temperatures and the frequency and volume of the sound emitted by snapping shrimp. (Image credit: Tom Kleindinst/ Woods Hole Oceanographic Institution)

As oceans around the world get warmer due to climate change, snapping shrimp are becoming louder than usual, creating “far-reaching implications” for various marine ecosystems, a new study has found.

Researchers at the U.S.-based Woods Hole Oceanographic Institution (WHOI) say this study is the first of its kind that looked into the relationship between rising temperatures and the frequency and volume of the sound produced by two snapping shrimp species.

The paper published Thursday in Frontiers in Marine Science was able to prove a clear relationship between the two and concluded that rising temperatures increase the sound of snapping shrimp.

Snapping shrimp are known to be one of the loudest marine animals and are widely found throughout tropical and temperate seas. Their “snapping” is a sound produced when they open and close their claw quickly, as a way to stun their prey, distract predators and even communicate with each other, according to a website by the University of Rhode Island’s Graduate School of Oceanography.

Researchers at the WHOI describe the sound as a “pervasive crackling noise that sounds like bacon frying.”

“These shrimp are the most ubiquitous sound producer in the ocean, and now we have evidence that temperature has a huge impact on their behaviour and the overall soundscape,” Ashlee Lillis, the paper’s co-author, said in a release.

“That’s relevant to everything from migrating whales to larvae trying to use the soundscape or humans who use the sea for extractive or military purposes.”

Fish finders and ship sonar are both affected by the constant popping noises created by snapping shrimp because their high volume covers such a wide acoustic spectrum, researchers say. According to the study, whales and dolphins may also use the sound of snapping shrimp to help them find their way down the shore.

Additionally, a variety of soundscapes are known to draw fish, shellfish, and coral larvae to suitable settling areas.

Lilis examined recordings of snapping shrimp from an oyster reef off the coast of North Carolina and discovered that for every Celsius degree increase in temperature, there was an increase of one to two decibels as well as a 15 to 60 per cent increase in snapping frequency.

When tested in a controlled environment, it was discovered that the snap frequency doubled with water temperatures between 20C and 30C, with some variations depending on the season or the shrimps' social grouping.

It is still unclear if shrimp will eventually adjust or how the increased snapping will affect their physiology or the environment in the long run because the experiments only mimicked the impacts of a brief heat wave, researchers say.

“Climate change is impacting the marine soundscape in fundamental ways,” T. Aran Mooney, the study’s co-author, said in a release.

“Warming waters can influence how animals are physically able to communicate and use sound to reproduce and attract mates. We don’t yet know what happens to the ecosystem when background noise levels are higher, but there are far-reaching implications.”