“Massive acoustic trauma.” It sounds like an ’80s metal band, but according to scientists at the Technical University of Catalonia in Spain, it’s what happens to squid and other cephalopods when they are exposed to sounds similar to boat noise. After exposing 87 cephalopods to low-volume, low-frequency noises for two hours, the researchers found damaged nerves, lesions, and other trauma in the creatures’ hearing organs. There are some holes in the team’s methods (see below), but if the findings hold, squid will be added to the long list of marine animals (including whales, dolphins, and crustaceans) endangered by human-made noise in the oceans. What’s the Context:
The team began the study (published in the journal Frontiers in Ecology and the Environment) after an unusual number of squid washed up on Spanish beaches. Boats had been prospecting for oil and gas nearby using air guns, and the researchers wondered if there was a connection. They exposed cephalopods to sounds that were similar to those produced by shipping, oil prospecting, and other common human activities in the ocean.
It was only recently that scientists confirmed that cephalopods can even hear (though they cannot hear as well as many other sea creatures, researchers found).
Noise pollution in the ocean has been acknowledged as a problem for years, but there haven’t been many changes in policy; the Supreme Court has ruled that the Navy could continue its sonar exercises despite the fact that its sonar was shown to damage dolphins’ hearing.
However, a connection between whale beachings and sonar use, frequently invoked by environmental groups, has not been borne out by the evidence: "Even if we know how they react to sound, it doesn't give us a good idea why they end up on the beach," says T. Aran Mooney, a marine biologist at Woods Hole Oceanographic Institution in Massachusetts (via ScientificAmerican).
Not So Fast: According to scientists interviewed byScienceInsider, the experiment has some flaws. The researchers don’t report much quantitative data, and they didn’t keep their control cephalopods in aquariums as they did with the sound-exposed cephalopods, which “leaves open the possibility that captivity, not noise, somehow injured the experimental animals,” says sensory physiologist Peter Madsen.
The new paper is "a good first step" in determining whether ocean noise from humans harms cephalopods, adds T. Aran Mooney, a marine biologist at Woods Hole Oceanographic Institution in Massachusetts...But he questions how the researchers measured the animals' exposure to noise. "If the National Marine Fisheries Service wanted to make a regulation based on this paper, they wouldn't be able to do it," he says. (ScienceInsider)
Reference: André et al. Low-frequency sounds induce acoustic trauma in cephalopods. Frontiers in Ecology and the Environment, 2011; 110408135918022 doi:10.1890/100124
Image: Flickr / Dan Hershman