The Sound From Ships May Attract Unwanted Critters

Hangers-on that cost the U.S. Navy $250 million a year

Barnacle Hull House

U.S. Navy via Flickr

A ship at anchor isn't necessarily quiet. Many crews leave their generators on while at anchor, to power refrigerators or air conditioners. But maybe they should consider shutting down, if they can. The thrum of a ship's generator can attract sea squirt larvae from as far away as 500 meters, according to a new study.

The little larvae are a big problem for ships. Sea squirts, barnacles, algae and other sea creatures that attach themselves permanently to boat hulls create excess drag that the U.S. Navy estimates costs it $250 million a year. The organisms also travel the world this way, spreading to ecosystems where they don't belong. Many groups are working on coatings for ship hulls that discourage hangers-on, but Australian fisheries scientist Justin McDonald recently looked at the problem from a different angle, Australian broadcaster ABC News reports. McDonald studied whether the noises ships make encourage sticky sea creatures.

By recording the sounds of ships at bay, observing where sea squirts attach, and studying sea squirts in the lab, McDonald and his colleagues determined that sound does matter. Coral reefs are actually quite noisy, so the squirt larvae may think grumbling ships are homey reefs, McDonald told ABC. They head toward the sound and settle on the first hard surface they find, and then they're there for life.