Noise pollution threatens to disrupt this pattern

May 17, 2010 14:27 GMT  ·  By
Coral larvae are attracted to the sounds associated with already-developed reefs, a new study finds
   Coral larvae are attracted to the sounds associated with already-developed reefs, a new study finds

Scientists have recently discovered that baby coral reefs tend to use special sounds as reference points in swimming to an already-established reef. While still in their larval from, the animals “listen” carefully to the sounds various other creatures living around reefs make, and then move directly towards them. According to a new research, this finding highlights another one of the factors currently threatening coral reefs, which are more and more often being drowned in artificially-produced noises, generated from human activities.

University of Bristol School of Biological Sciences senior researcher Dr Steve Simpson found a few years back that fish species adapted to living around corals were capable of using various sound cues to make their way to their destination. However, even for him, the new discovery came as a surprise. The work was carried out in the Dutch Antilles, by a team based at the Carmabi Foundation, in Curacao. The group there, led by Dr Mark Vermeij, conducted its investigation of coral larvae that scientists collected in 2008, during a mass-spawning event, ScienceDaily reports.

“At close range sound stirs up water molecules, and this could waggle tiny hair cells on the surface of the larvae, providing vital directional information for baby corals,” Simpson explains. While in their larval form, baby corals are about the size of fleas, and extremely vulnerable. If they cannot find a secured place within a reef to attach themselves to, they die relatively fast. It is vitally important for as many larvae as possible to make it into reefs, if global coral populations are to survive the myriad of environmental factors that continuously batter them. But noises generated by humans and their vessels make the job very difficult, and many larvae cannot find a suitable place to affix themselves on.

In the new experiments, researchers set up a “choice chamber,” in which larvae were presented with more options, and allowed to choose whichever they pleased. A recording was played back, that featured the natural sounds of coral reefs. The investigators noticed an overwhelming trend among the coral larvae to swim in the direction of the sounds, ignoring other options. The new study was funded by the Natural Environment Research Council (NERC), the US National Science Foundation (NSF), and the Scripps Institution of Oceanography. Details were published in the latest issue of the open-access scientific journal PLoS ONE.