Noisy Oceans Could Traumatise Squids

Giant squids are fascinating, deep sea creatures that are so elusive that a live one was photographed for the first time just last year. So it was very unusual for the people of  Asturia, in northern Spain to encounter five giant squids on their beaches in 2001. The squids were dead, and the carcasses washed ashore over a two-month period. Four more carcasses were found in 2003.

(Read more about stranded squids in the Atlantic here. And read about the myths inspired by giant squids and the search to learn more about them here.)

The deaths were mysterious. But the carcasses offered one clue to the possible cause. Each animal showed signs of injuries to an organ called the statocyst. It is like a primitive ear that squids use to balance and orient themselves underwater.

That, along with the fact that both stranding events were around the same time that ships were exploring for oil and gas with low frequency airguns, got scientists suspecting that sound from the ships had injured and subsequently killed the squids.

So, marine bioaccoustician Michel André of the Technical University of Catalonia in Spain decided to investigate. André and his colleagues worked with fishermen to catch and bring back 87 squids belonging to four different species, and exposed them to low frequency sound for two hours. The frequency of sound used (50-400Hz) was in the range used by the ship airguns (below 100Hz).

A later analysis of the animals’ statocysts revealed varying extent of injury, including damaged sensory hairs. The extent of damage worsened over time in animals that were kept alive longer after the exposure to sound.

André says he was expecting to find some impact on the statocysts. “But we were surprised to find such massive trauma.” The animals did not eat anything after the injury, he says. “They were just floating, with no motion.”

So how did the statocyst injuries lead to death? André suspects the animals’ lose their sense of balance when the statocysts can’t function. But only future research will reveal if that is indeed the case, he adds.

The findings were published today in Frontiers in Ecology and the Environment.

The new study does demonstrate that squids can be affected by anthropogenic noises, says Jason Gedamke, the manager of the U.S. National Oceanic and Atmospheric Administration (NOAA)’s Ocean Acoustics Program. “But… it may be a bit of a stretch” to use André’s results to interpret what happens to squids (giant and otherwise) in noisy ocean environments, he adds.

For over a decade, scientists have been learning more about ways that human-made sounds like sonar and other ship noises can harm marine animals. But the bulk of those studies have focused on marine mammals, like whales and seals that use sound to communicate with each other. (I also found a couple studies on some non-mammalian species: one on fish, another on crayfish.)

We have very little information on invertebrates like the Cepaholopods, says Gedamke. And the new study highlights the need to do more research on the impact of ocean noise on marine invertebrates.

(For more on how other marine science experts are viewing Andre’s paper, see this news story on Science magazine’s online news.)

More on noise pollution:

We’ve been covering the terrestrial impacts of noise pollution (mostly how they impact birds) in our weekly science podcast. Listen to those stories here and here.

Tags: giant squid, low frequency sound, marine conservation, noise pollution, noisy environment, ocean, oil exploration, sea, squid