The sound of reefs essential for corals

We tend to think about corals as stationary animals, almost plants, but they do have a free-swimming stage when they are very young. A team of scientist working in the Caribbean Sea has now found that during this stage, the tiny corals find their way to suitable homes by listening to the distinctive sounds produced by reef dwelling animals.

The big question is now if the increasing noise pollution of the ocean brought on by human activities will affect the corals’ ability to find suitable spots for colonization. If free-swimming corals do not find a spot soon enough they die, and promptly being able to locate a fitting surface is therefore of outmost importance for them. Numerous human endeavours pollute the sea with various sounds, from boating and shipping to drilling, pile driving and seismic testing.

A few years back, Dr Steve Simpson, Senior Researcher in the University of Bristol’s School of Biological Sciences, was able to show that reef fish utilize sound to locate coral reefs in the ocean. The Carmabi Foundation Team working in Curaçao in the Dutch Antilles wanted to see if this was true for corals as well, and therefore set up a ‘choice chamber’.

A choice chamber is a device where small invertebrates, such as corals, are given the option to choose between two or more different conditions. The Carmabi choice chamber was filled with coral larvae belonging to the species Montastraea faveolata, the main reef building coral in the Caribbean Sea. The scientist then played recordings of a coral reef, and the corals turned out to very much favour moving in the direction of the sound.

Free-swimming corals are tiny and look a bit like miniscule hairy eggs. How they manage to detect sounds remains unknown.

“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,” said Dr Simpson.

The results of the study, which was headed by Dr Mark Vermeij, has been published in PLoS ONE.

http://www.plosone.org/home.action

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0010660

The research was funded through a fellowship to Dr Simpson by the Natural Environment Research Council (NERC, UK) and by the National Science Foundation and Scripps Institution of Oceanography (USA).

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