DragonI

Scientists lure fish to dead reefs using speakers playing healthy coral sounds

Underwater speakers playing healthy reefs noises double the amount of fish on damaged reefs, giving scientists hope that sound could be used to help restore them.

www.abc.net.au|Nick Kilvert

• Fish numbers doubled and species increased by 50 per cent on acoustically "enriched" sites
• Coral polyps have also been found to navigate toward healthy sounding reef, despite not having ears
• Bigger stressors like climate change, pollution and overfishing still need to be addressed

Researchers have used the sounds of healthy reefs to entice fish back to areas where coral has been wiped out on the Great Barrier Reef.

They took recordings of shrimp snapping, fish grunting and other sounds taken from healthy regions of reef and played them on underwater speakers at a bunch of "coral-rubble patch reefs" at Lizard Island.

The number of fish doubled at the sites where they placed the speakers compared with control sites with no audio over the 40-day study period, they reported in Nature Communications.

They also found the number of different types of fish — the species richness — increased by 50 per cent during that time.

The researchers hope their findings may help in restoring some of the ecosystem functions to coral reefs that have suffered bleaching or been hit by cyclones or other impacts, said Tim Gordon, lead author and PhD student from the University of Exeter.

"Attracting fish to a dead reef won't bring it back to life immediately. But recovery is underpinned by fish that can clean the reef and create space for corals to regrow.",  Dr Mark Meekan

To move reef recovery beyond localised applications such as this one, the bigger issues must be fixed, Professor Nagelkerken said.

"It doesn't solve the greater issue of how we are [harming] the oceans via pollution, climate change and ocean acidification, habitat destruction and overfishing," he said.

"If we don't remove those stressors then reef restoration is not going to happen."

The sounds that come from the Northern Great Barrier Reef have got quieter in the last five years, scientists at the University of Exeter have found.

The noises, which are made by sea creatures, help young fish find their way home.

Acoustic waves warn of tsunami

www.sciencedaily.com

An early warning system against tsunamis has been developed and tailored for the need of the Mediterranean, but preparedness on the ground is paramount to ensuring peoples’ safety.

... an EU funded project called NEAREST found a better way of identifying a tsunami threat at early stage. "To do this we developed a new device we called tsunameter that we put as close as possible to those places where we know that is very likely a tsunami is generated," says Francesco Chierici, who is the project coordinator and also works as a researcher the Radio Astronomy Institute (IRA), in Bologna, Italy. This tsunameter can be placed close to the geological faults that are responsible for the earthquake and, accordingly, for tsunamis. Detecting a tsunami near its source is crucial "especially in peculiar environments such as the Mediterranean where the tsunami are generated very close to the coasts," says Chierici.

Every device is connected with a surface buoy and consists of a set of instruments collecting several kinds of data. These include local acceleration and pressure of water, seismic waves, and, in particular, the acoustic waves generated by tsunamis.With this information, actual tsunamis can be distinguished from the background noise, "using a specific mathematical algorithm" which is interpreting the data. Under the project, the tsunameter had been tested for a year off the Gulf of Cadiz in Spain, at water depth of 3,200 metres. Since the project was completed, in March 2010, the tsunameters are now tested in a new research programme called Multidisciplinary Oceanic Information SysTem (MOIST), run by the Italian National Institute of Geophysics and Vulcanology(INGV) in Rome.