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Sunday, May 16, 2010

(C)oral Arguments

So we already traipse en masse all over delicate seaside organisms, befuddle nesting turtles with obscene amounts of light, and cut the olfactory trails that lead baby anemone fish home.

Now, it turns out, the noise we make might be luring baby corals away from their habitats.

Lots of buzz about some (mostly Dutch) scientists concluding that baby corals don't just float passively but somehow direct themselves toward the sounds of a reef -- the clicking, snapping, etc. It's not clear that it's "swimming," exactly, but they're orienting themselves to get to where the action is.

"Discover Magazine's" website had the details, but "The Guardian" and others carried the news, too.

Here's the best of's blog post:
It seems bizarre that a simple coral larva could hear sound but we’re probably still thinking about these animals as rocky reefs rather than the living animals they encase. Previous studies have shown that coral larvae can see (detect light), touch (respond to textures) and smell (detect chemicals). Now, we know that they can also hear. Vermeij thinks that they do it with tiny hairs called cilia that coat their bodies.

As sound waves move through the sea, they cause water molecules and other particles to move up and down. These jiggling particles waggle the cilia, telling the corals where to head.

For the moment, it’s not clear if the larvae can tell the difference between reef sounds and general underwater noises. That’s an important question because the oceans are becoming noisier places, thanks to shipping, industry, drilling and military tests. This cacophony can easily drown out the sound of shrimps and fish. Underwater noise pollution already poses a problem for many animals including whales and dolphins. Do corals, many of which are already facing extinction, face the same problems?
Many already suspect that whales are being adversely affected by the sonar (and other) bombardments from military activities. It's achingly clear to anyone who's spent any time at all under a popular dive site as boats jockey for position that such hot spots feel like the pits at the Indianapolis 500. How's a little larva supposed to cope?

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