Noise in Oceans Leads to "Severe Acoustic Trauma" in Octopus, Squid

Jeremy Hance
mongabay.com
April 12, 2011

Researchers have documented for years how noise pollution impacts dolphins in whales, but a new study in Frontiers in Ecology and the Environment finds that even low intensity noise can severely injure cephalopods, which include octopus, squid, and cuttlefish. The injuries are bad enough to possibly lead to stranding and death, thereby providing a feasible explanation for a number of recent strandings, including giant squid washing ashore in Spain.

"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," says Michel André, Technical University of Catalonia in Barcelona, in a press release.

Researchers subjected four species of cephalopods—European squid (Loligo vulgaris), common cuttlefish (Sepia officinalis), common octopus (Octopus vulgaris), and Southern shortfin squid (Illex coindeti)—to low intensity and low frequency sounds (between 50 and 400 Hertz) for two hours. Following the noise exposure, researchers found damage to species' statocysts, which are sensory organs that balance the cephalopods. Inside the statocysts hair cells had ruptured, nerve fibers had swelled, and some statocysts even suffered lesions. These holes continued to grow larger hours after exposure.

The European octopus, and other cephalopods, are more sensitive to even low-frequency sounds than researchers expected. Photo by: Gewöhnlicher Krake. “We expected some lesions after noise exposure but not the level of trauma that we found. What we found was typical of what you might find in mammals after violent, high intensity sound exposure,” André told The Great Beyond.

Given the low intensity of the sounds used in the experiment, researchers believe the 'louder' sounds encountered in the ocean would significantly impair squids, octopi, and cuttlefish.

"The impact of continuous, high intensity noise pollution in the oceans could be considerable. For example, we can predict that, since the statocyst is responsible for balance and spatial orientation, noise-induced damage to this structure would likely affect the cephalopod's ability to hunt, evade predators and even reproduce; in other words, this would not be compatible with life," André explains.

Underwater noise pollution is caused by offshore drilling—and other excavation activities that use seismic surveys to locate deposits—cargo transportation, industrial fishing, and even recreational boating. Studies have shown that some marine animals actually become louder to be heard when confronted with deafening sounds in their environment.

"It left us with several questions," André says, "is noise pollution capable of impacting the entire web of ocean life? What other effects is noise having on marine life, beyond damage to auditory reception systems? And just how widespread and invasive is sound pollution in the marine environment?"