Mysteries and music: Listening in to underwater life

When marine researchers started recording sounds in the seagrass meadows of the Mediterranean Sea they picked up a mysterious sound, like the croak of a frog, that resounded within the dense foliage and nowhere else.

"We recorded over 30 seagrasses and it was always there and no-one knew the species that was producing this kwa! kwa! kwa!" said Lucia Di Iorio, a researcher in ecoacoustics at France's CEFREM.

"It took us three years to find out the species that was producing that sound."

The melodious songs of whales might be familiar music of the world's underwater habitats but few people will have heard the hoarse growl of a streaked gurnard or the rhythmical drumbeat of a red piranha.

Scientists are now calling for those sounds and many thousands more to become more widely accessible.

They say a global database of the booms, whistles and chatter of the sea will help to monitor diversity in aquatic life and help put a name to mystery sounds like the one Di Iorio and her colleagues investigated.

Experts from nine countries are working to create what they have dubbed the Global Library of Underwater Biological Sounds or "GLUBS."

This would gather together recordings held all over the world and open them up to artificial intelligence learning and mobile phone apps used by citizen scientists.

While experts have been listening to life underwater for decades, the team behind GLUBS say that audio collections tend to be narrowly focused on a specific species or geographical area.

Their initiative is part of burgeoning work on marine "soundscapes" -- collecting all the sounds in a particular area to discern information about species types, behaviour and overall biological diversity.

Scientists say these...