Jan 16, 10:36 PM

Glider may be a red tide finder

By Kevin Lollar Gannett News Service

SARASOTA -- Cruising slowly through the green Gulf of Mexico on Wednesday, the bright yellow Slocum glider looked menacingly military.

But the $80,000 autonomous underwater vehicle (AUV) is nothing more than a sophisticated scientific instrument with which Mote Marine Laboratory hopes to detect red tide. Mote scientists and scientists from Rutgers University concluded three days of field tests on the glider Wednesday.

If data show the glider works as advertised, this summer, Mote will install a $20,000 red tide detector that will transmit almost continual data about red tide in the Gulf from Tampa Bay to Charlotte Harbor.

Red tide is a natural phenomenon that occurs when an alga called karenia brevis, or k. brevis for short, undergoes a population explosion. During these algal blooms, k. brevis releases a powerful toxin that renders shellfish inedible, can kill fish and cause respiratory irritation in humans.

Brevard County and other eastern Florida beaches experienced an outbreak of red tide for about six weeks beginning in early November.

"The key to this project is mitigating harmful effects of red tide," Mote senior scientist Gary Kirkpatrick said. "For example, for clam farmers, if they know red tide is out there, they can get their clams out of the water before it comes inshore. If they get a couple of days warning, they can save their harvest."

Despite its sophistication, the Slocum glider, developed by Webb Research Corp. of Falmouth, Mass., works in a pretty simple way. Scientists set it on a course by programming a series of coordinates into its GPS system. When the AUV is in the water, battery-operated pistons draw water into its cylindrical body, which causes it to sink.

Swept-back wings give the glider forward momentum as it angles toward the sea floor. When it reaches its pre-programmed depth, the pistons pump water out, and the AUV rises to the surface to send its data to a satellite.

Water is pumped back in; the AUV descends again.

A Slocum glider, named for Capt. Joshua Slocum, who sailed alone around the world in a 37-foot sloop in the 1890s, can be at sea unattended for 30 days.

When the red tide detector is installed, Mote will send the glider on missions in areas where satellites have detected chlorophyll, which indicates the presence of algae.

"But the satellite doesn't know whether it's red tide algae or background algae," Kirkpatrick said. "So, when the satellite sees something interesting, we'll program these guys and say, 'Go to such-and-such coordinates and see what it is.' "

Mote would like to have three AUVs, which will greatly increase the ability to monitor red tide in Southwest Florida.

Rutgers already has instruments on the gliders to test for such things as salinity, temperature and dissolved oxygen, and Rutgers scientists will be working with Mote on the red tide detection project.

"I think red tide is awesome," said Oscar Schofield, a Rutgers professor of oceanography. "My training is in phytoplankton, so my life is scum. It's nice to see that this scum has become important. The great thing about red tide is that it's an ecological problem -- why is this alga doing better than other algae? It's theoretical science, but it's also applied science: Science helping a local problem."

The National Science Foundation is footing the bill for the gliders, and the National Oceanic and Atmospheric Administration is financing the research end of the project. When Slocum gliders start cruising around the Gulf this summer, they might pop to the surface near a boat and baffle those on board.

"If you hook one or catch it in a net, just put it back in the water," Kirkpatrick said. "If a wing is broken, there are phone numbers on it you can call. If you see one, leave it alone. Take pictures if you're curious, then let it go on its mission."