Underwater construction is dangerous for salmon swimming to spawning grounds. Luckily, we can help.
Noise pollution is a proven health risk, which is why citizens living under flyways often receive subsidies to have their homes insulated against airplane roars, and cities put up barrier walls along busy roads that abut residential neighborhoods. We’re not the only species that gets stressed out and sickened by loud sounds. Fish, for instance, can be physically damaged by human noise, whether it’s coming from an underwater pile driver or a commercial barge.
In Pacific coastal rivers, according to the Portland Mercury (Aug. 4, 2011), salmon trying to reach their spawning grounds can experience internal hemorrhaging or bruising from the clatter of underwater construction. To help alleviate the problem, federal law dictates that bridge building in the area—such as the light rail link being built over the Willamette River in Oregon—must take place during a four-month period in the summertime when salmon migration is limited.
Farther off coast, squid and octopuses can have their organs pulped by the powerful low-frequency din of shipping, oil, and gas vessels, explains Scientific American (Sept. 2011). Since creating noise-free time zones isn’t an option, acousticians like Mark S. Wochner of the University of Texas at Austin are experimenting with placing a physical sound barrier between the noise source and the delicate marine creatures.
One barrier type they’re trying out is essentially a big bubble of air encased in thin latex, similar to a balloon, which would be placed in layers around noisy barges, ships, and offshore wind farms. “Tests performed on these latex bubbles inside laboratory tanks show that layers of them could muffle sound by 44 decibels,” reports Scientific American, “the difference between a busy city street and a library.”