Go to the beach on a summer day. Listen to the sounds—the waves crashing, children shouting, seagulls squawking. Now go underwater.
The undersea world, of course, is not truly devoid of sound. The ocean is literally awash with noises of all kinds: the explosion of a crashing wave, the clicks and whistles of chattering dolphins, the crunch of reef fish grazing on algae—and each other. Go snorkeling on a coral reef and you’ll experience a never-ending symphony of snaps, crackles and pops. In some ways life on the reef must be like swimming in a bowl of Rice Crispies.
I read an interesting article about undersea noise in a recent issue of Conservation Magazine, published by the Society for Conservation Biology. The author describes the ecological importance of sound in the ocean—many fish make noise to attract mates or scare off predators (just like terrestrial species), and some larval reef fish, born in the open ocean, find their home by following the sounds of the coral reef. It reminded me of a friend who had a similar theory about kelp forest fish. He speculated that the kelp-crunching jaws of the purple sea urchin (Strongylocentrotus purpuratus) made a sound that was amplified through their test (the shell), which larval kelp forest fish could follow to find their way home, just like their coral reef relatives.
The sounds of the ocean may seem strange to you or me, but marine species depend on them. The ecological importance of natural undersea noise is not yet well understood, but increases in maritime traffic, underwater construction, and seismic and sonar operations are making the ocean a louder place. Imagine never being able to ask someone out on a date because you can’t be heard over the din of traffic and construction.
Could anthropogenic sea noise hinder the survival of wildlife in marine protected areas? Sound in the ocean travels farther and faster (5x faster) than in air. Plus, the author in Conservation discusses evidence that ocean acidification will deplete sound-absorbing chemicals in the water, allowing it to travel even farther. MPAs generally limit noisy activities such as shipping and underwater construction in their proximity, but if acidic waters broadcast anthropogenic noise far and wide, could it hinder the ability of larval fish to even find their way home?
Maybe this one instance where the only solution to anthropogenic sea noise is to turn it down. What do you think?
Here is the link to read the article ‘Aural Fog’ in Conservation Magazine: http://www.conservationmagazine.org/2011/03/aural-fog/
Here is the link to the scientific paper by Steven Simpson referenced in the article: http://www.int-res.com/articles/meps2004/276/m276p263.pdf