USF researchers from the College of Marine Science returned Friday from an eight-day expedition to the Pulley Ridge reef situated approximately 100 miles offshore of Naples. Pulley Ridge reef is the deepest U.S. coral reef and is situated between 250 and 300 feet deep.

According to John Ogden, director of the Florida Institute of Oceanography, before this expedition the Pulley Ridge reef “has never really been seen in its biological splendor.”

The team of researchers from USF was joined by others from the Florida Institute of Oceanography, U.S. Geological Survey, Mote Marine Laboratory and the Harte Institute of Texas A&M.

The multi-institutional team worked toward three common goals: completing a geo-physical survey of the reef, using divers to explore and photograph particularly interesting areas of the reef and to bring back samples of coral, algae and other organisms, Ogden said.

The coral reef thrives on the rocky remnants of an ancient barrier island believed to have been submerged after the last glaciation, said Al Hine, assistant dean of the College of Marine Science.

“As sea levels continued to rise and water in the Gulf got warmer, corals could form on the hard substrate,” he said.

The reef is located beneath a strong current off the Gulf Stream known as the loop current. Hine explained how light-dependent corals could form at such extreme depths.

“(The reef) is bathed by very clear water and there is a hard substrate down there on which the corals can form,” he said.

The reef has been protected to some degree because of its designation by the National Oceanic and Atmospheric Administration as “a habitat of concern, and that means certain things can not be done, but it’s not a full blown sanctuary,” Hine said.

“With the geo-physical work, we tried to see how extensive (the reef) was,” Hine said. “Divers can only cover a tiny portion of the seafloor, especially since when you go down 200 feet you’re only allowed about 20 minutes. So you can’t really do much exploring, but you can do it by remote sensing.”

A number of exciting research techniques were applied during the time on Pulley Ridge reef such as side scan sonar, a remotely operated vehicle (ROV) and a small single-man submarine.

“Side scan sonar illuminates, with sound, the sea floor and that sound is reflected back to a transducer. Then it all goes into a computer and it makes a map,” Hine said.

Hine said there will be much more research of the Pulley Ridge reef in the future. Not only in the water, but also back in the lab, before any conclusions could be fully reached.

“A research project typically produces more questions than answers, and this was a reconnaissance mission,” Hine said.