Ever wonder how coral reefs get so richly populated with marine life? Apparently, part of the coral reefs' appeal comes from the small sounds its inhabitants help make — even if human ears can't hear them. A new study from marine biologists finds that coral larvae can use their tiny hairs — a.k.a. "exterior cilia" — to "hear" reefs and move towards them. Reports the L.A. Times:

Though humans swimming by a coral reef might hear only the bloop-bloop of their own air bubbles, that's because human ears aren't well suited to hear underwater, said senior author Stephen Simpson, a marine biologist at the University of Bristol. But as fish scrape the surfaces of the reef and communicate with one another through popping noises, snaps, grunts and chirps, they produce "a real cacophony of noise" to other marine life, Simpson said.
Unfortunately, the coral larvae's sensitivity to sound means that human noise could be leading these baby corals away. "Many coral reefs worldwide have been dying, and Simpson pointed out that human activity in the ocean could be making enough noise to interfere with the baby coral's ability to find safe places to settle," reports the L.A. Times.

We've been getting a lot of bad news about coral reefs lately, what with the Gulf Coast oil spill's effects on Florida's coral reefs and the combined effects of global warming. But green activism to reverse the damage — from Disneynature's efforts to save 35,000 acres of coral reef to Delaware's artificial reef program — forges on. Can you hear the sound of one coral larva swimming?

The sound of one coral reef growing
Baby corals can "hear" coral reefs and swim towards them, researchers find. Unfortunately, human noise may be impeding this natural instinct.