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We know that marine noise pollution from Navy ships and oil exploration vessels cause disorientation and death for whales and other marine species. But for the first time, scientists have proof that the spat of giant squid deaths witnessed a decade ago were also caused by strong, low-frequency noises. Evidence that Noise Kills Giant Squid and Other Cephalopods
When giant squid washed up ashore along Spain's Asturias province in the early 2000s, the events occurred suspiciously close to when ships had used air guns to conduct low-frequency sound-pulse exercises in the region, Ocean Leadership reports. While the noises were a possible cause for the squids' deaths, it was not confirmed until a recent study completed by Michel André, a marine bioacoustician at Barcelona's Technical University of Catalonia and his team.
A History of Harming Marine Animals with Noise Pollution
We have known for some time that whales and other marine mammals which rely on sound for communication and navigation have been harmed by the noise pollution in the ocean -- either by not being able to hear, and therefore find, one another, or by being so blasted by loud sounds that they beach themselves or are killed by the trauma caused inside their skulls. More recently, we've discovered that noise pollution can even cause harm to fish larvae by leading them away from good habitat.
But now, we're becoming ever more aware of the destructive effects of human noise in the ocean. Evidence shows that giant squid and other cephalopods are susceptible to injury and even death from noise.
"We know that noise pollution in the oceans has a significant impact on dolphins and whales [which use natural sonar to navigate and hunt]. ... but this is the first study indicating a severe impact on invertebrates, an extended group of marine species that are not known to rely on sound for living," André said in a statement.
Yep, Squid Can Hear!
Last year, TreeHugger Christine pointed us to research from Woods Hole Oceanographic Institution, which questioned if squids can hear.
Mooney's research indicates that squid do hear. But they detect noises only up to about 500 Hz. Compare that to human hearing, which detects sounds ranging from 20 Hz to 20,000 Hz. More importantly, this implies that squid do not hear the higher frequency sonar impulses used by dolphins and whales for echolocating their prey. The squid probably first "hear" their predators when the compression wave pushed ahead of the swimming creatures strike them -- too late to maneuver away. Which leaves the squid as sitting ducks on the saline smorgasbord.
But it turns out, squids are more effected by sound than we once thought. Ocean Leadership reports that the latest study provides proof that the ship exercises in the early 2000s were the direct cause of the bodily harm done to the washed up squid, which included "mantles reduced to pulp, bruised muscles, and lesions in statocysts. These fluid-filled organs rest behind the creatures' eyes and help giant squid maintain balance and position."
An Experiment On Squid, Octopus and Cuttlefish
The study showed that among specimens of two species of squid, one species of octopus and one species of cuttelfish exposed to low-frequency sound for two hours, all showed signs of damage to their statocyst tissue, with the damage becoming worse the longer after exposure the animals lived.
"This is a typical process found in land mammals and birds after acute noise exposure: a massive acoustic trauma followed by peripheral damage, making the lesions worse over time," André said.
The experiments prove that squid are indeed harmed by human-created noise pollution in the ocean. As evidence mounts as to how much of an impact we're having on marine life by our loud activities, will we ever make an effort to shush up?
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More on Noise Pollution
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