The Latest from SCUBA Diving News

Global warming turns fish deaf

Is it important that global warming turns fish deaf?







Yes. For coral reef fish, sound is vital for them to judge where to settle down and live.

After hatching, reef fish larvae are dispersed by ocean currents for a few weeks. The larval fish must then find their way back to a suitable reef to make their home.

It's thought that the young fish home in on high-frequency noises. Coral reefs are extremely noisy environments, with the crackle of snapping shrimps and the chatter of fish set against a backdrop of wind, rain and surf. Sound carries well underwater, and most fish have great hearing.

Global warming and more acidic oceans, though, can cause fish to be born with deformed earbones. Reasearchers at the Australian Institute of Marine Science in Townsville and the University of Edinburgh, suspected that it might be harder for these fish to pinpoint the origin of a sound, increasing the chance they would get lost in the ocean. And, indeed, their results show that this is so.

Journal References and Further Reading:
Proceedings of the Royal Society, Volume 275, Number 1634 / March 07, 2008
Animal Behaviour, doi:10.1016/j.anbehav.2007.11.004
SOUND: The essential navigation cue for young reef fishes to find their way home

Laser spots decompression sickness

 

Decompression sickness, it not treated quickly, can cause lasting damage and may even be fatal. Instead of waiting for symptoms to appear, a University of Houston professor is developing a laser-based system that can diagnose decompression sickness in a matter of seconds.

Kirill Larin, assistant professor of biomedical engineering and mechanical engineering, is using a $400,000 grant from the U.S. Navy to develop the first optical non-invasive tool to test those most likely to suffer from decompression sickness, such as SCUBA divers, submariners and airplane pilots. Decompression sickness affects those who experience sudden, drastic changes in the air or water pressure surrounding their bodies. It can cause anything from joint pain – known as the bends – to seizure, stroke, coma and, in the most extreme cases, death.

“Most of the time, decompression sickness isn’t addressed until the person starts showing clinical symptoms,” Larin said. “It would be better, of course, to treat the problem before the symptoms appear. That would allow individuals to take the appropriate medical actions to reduce the side effects of decompression sickness.”

Larin’s optical device can locate microbubbles of nitrogen gas in blood and tissues, which can restrict the flow of blood throughout the body and cause harm. Larin is developing the tool, which works much like an ultrasound machine, with Dr. Bruce Butler of the UT Health Science Center in Houston. Instead of getting readings using sound waves, however, Larin’s system uses light waves in the form of lasers that bounce back when they encounter resistance, thereby providing a high-resolution image.

The Navy could eventually use this technology on all divers or pilots returning to the surface. By shining the laser on one of these individuals, it would provide an image that would reveal the presence of any microbubbles in the blood or tissue – all in a matter of seconds. If microbubbles are found, then medical steps, such as time in a decompression chamber, could be taken before the symptoms appear.

An early version of the tool has been able to locate microbubbles as small as six micrometers, or six thousandths of a millimeter. Most microbubbles are between five and 15 micrometers, about the size of a red blood cell.

With continued research, everyone from highly trained naval divers and pilots, to astronauts and recreational SCUBA divers could benefit.