Newswise — A team of researchers from the University of South Florida's College of Marine Science, the Florida Institute of Oceanography, the U.S. Geological Survey, Mote Marine Laboratory and the Harte Institute of Texas A&M University, returned to USF's Bayboro Harbor July 1 after an eight-day reconnaissance mission to Pulley Ridge, a 225 mile long feature extending along the west Florida shelf in approximately 250 feet of water. The shelf supports multiple ancient shorelines submerged when sea levels rose due to melting ice after the last glaciation over 13,000 years ago. The southernmost 25 miles of Pulley Ridge supports active coral growth that comprises the newly-discovered deepest reef in U.S. waters.
"The expedition had three objectives" explained John Ogden, FIO director. "We wanted to map the reef and photograph it with state-of-the-art digital cameras and bring back samples of the reef and algae."
The research team combined resources to analyze the biology and geology of the parts of the shelf. While researchers aboard "RV Suncoaster" documented seafloor biology, Al Hine, associate dean of research at the College of Marine Science, was aboard "RV Bellows," where efforts to map the seafloor along Pulley Ridge revealed four ancient shorelines dating back to when sea levels in the Gulf of Mexico were 400 feet lower than today.
"During the last glaciation, ice melted unevenly in North America," said Hine, a geological oceanographer. "This caused multiple rises of sea level, creating successive shorelines, like bathtub rings."
Hine said the successive shorelines, 100 miles off Florida coast, still stand seven to eight meters high submerged between 60 and 90 meters below the surface. In appearance, the series of shorelines are not unlike the barrier islands off west Florida.
"They did not erode - as so many barrier islands do - but became submerged and served as the hard substrate on which coral reefs could be built," explained Hine.According to Hine, crews on both vessels worked in shifts, 24 hours a day, for the duration of the expedition.
"The shelf is bigger than the state of Florida," said Hine. "We wanted to cover as much as possible."
A number of environmental conditions helped establish the reef.
"The exceptionally clear water along Florida's southwest coast allows sunlight to penetrate to 250 feet below the surface where photosynthesis can take place, creating a symbiotic relationship between the algae and coral," said Ogden. "Coral is a living organism and needs light to live.
Biologists aboard the "RV Suncoaster" brought back samples of algae thought to be rare in the Gulf of Mexico, a possible new species of coral, unusual mollusks and seafloor "reef worms," which may be newly discovered species.
The announcement in January of the unique reef's discovery made a big splash in marine science circles and in the media.
Besides the two FIO research vessels, the expedition included a mini submarine for photography, a remotely operated vehicle (ROV) for mapping operations and several scuba divers, who breathed a special mix of gasses to allow them to work between 250 and 300 feet down while collecting samples.
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