Ocean acidification could have a major impact on creatures that live in these waters throughout the world. Now, scientists have found that snapping shrimps, which are the loudest invertebrates in the ocean, could be silenced by acidification.
"Coastal reefs are far from being quiet environments-they are filled with loud crackling sounds," Tullio Rossi of the University of Adelaide said. "Shrimp 'choruses' can be heard kilometers offshore and are important because they can aid the navigation of baby fish to their homes. But ocean acidification is jeopardizing this process."
The snapping shrimp is one of the noisiest marine animals in these ecosystems. In fact, they can produce sounds of up to 210 decibels when they form bubbles due to the rapid action of their snapping claw. This is often used as a warning to scare predators or used when they're hunting other creatures.
Scientists have long known that ocean acidification could impact creatures that form a calcium carbonate shell. But how would it affect these shrimp? The researchers measured the sound produced by shrimp in field recordings at natural CO2 volcanic vents in three different ocean locations. They also measured the sounds under laboratory conditions.
What did they find? At these CO2 volcanic vents, the ocean is more acidic, which gives researchers a natural laboratory in which to conduct their tests. Surprisingly, they found that there were substantial reductions in the levels of sound produced in addition to the frequency of snaps.
"Our results suggest that this is caused by a change in behavior rather than any physical impairment of the claw," said Ivan Nagelkerken, one of the researchers. "This outcome is quite disturbing. Sound is one of the most reliable directional cues in the ocean because it can carry up to thousands of kilometers with little change, whereas visual cues and scents are affected by light, water clarity and turbulence. If human carbon emissions continue unabated, the resulting ocean acidification will turn out currently lively, noisy reefs into relatively silent habitats. And given the important role of natural sounds for animals in marine ecosystems, that's not good news for the health of our oceans."
The findings are published in the March 16 issue of the journal Proceedings of the Royal Society B.
