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Pulley Ridge coral off the Keys has scientists puzzled

They have embarked on a scientific armada to the deepest coral reef in the continental United States.

Associated Press
Published August 21, 2005


OFF THE FLORIDA KEYS - A small craft hovers over a slimy purplish red creature feeding on small organisms as a diver combs the dark terrain, scooping up a spineless creature that looks so bizarre, it couldn't possibly be from Earth.

The vessel and explorer drift off into the cobalt blue abyss in search of more species.

"We've got worms," a voice from the vessel radios to the mother ship, as the sub crosses a field of tubular white invertebrates.

A small red grouper swims by, reminding the diver that he's not on Mars or the moon, but exploring a coral reef hundreds of feet deep in the Gulf of Mexico. The reef offers as many questions for scientists as space but is, to some degree, less explored.

Few people have made the 250-foot descent to Pulley Ridge, the deepest coral reef in the continental United States. Fishermen knew it was a grouper and tilefish habitat and that there were sponges, but it was not until recently that it was really visited.

A submersible vessel made the journey in the late 1990s, allowing scientists to see it. Recently, a few brave souls dove the reef and for the first time man was able to touch it. The trip also led to the most profound research of the area ever, scientists said.

A collection of the world's leading coral ecologists, scientists and divers embarked on a scientific armada to Pulley Ridge, 150 miles west of the Dry Tortugas. The goal was to search the sea floor in search of coral, fish and other unusual sea life that call the reef home.

The research trip was reminiscent of early space exploration of the 1960s. Instead of a moon rover and space suits, they had a one-person submersible, a remote operating vessel and some of the most high tech diving gear the world has to offer.

Key West naturalist diver and Explorers Club fellow Tim Taylor and Mote Marine Laboratory scientist Jim Culter led a hand-picked group of highly experienced "tech divers" to serve as scouts and sample collectors on the expedition. Divers worked in conjunction with scientists explored the bottom in a $1.5 million submersible research vessel and a remote control vessel.

Crews worked through the night to process samples and made one of the expedition's most interesting findings with the help of the night skies: the discovery of a bioluminescent algae that could yield clues to the corals' health. Sylvia Earle, an oceanographer and the National Geographic Society's explorer-in-residence, called the reef "enormously rich with life and diversity."

"It's like a beautiful garden," said Earle, who viewed the reef the first time via a submersible in the late 1990s on a National Geographic/NOAA Sustainable Seas Expedition.

The coral on the reef is exceptionally healthy compared with many shallow reefs in the Florida Keys and Caribbean. The reef may be isolated from the mainland but it is not immune from some of its problems. And the reef sits downstream from the notorious "dead zone" that forms each year in the Gulf at the mouth of the Mississippi River. However, strong currents, clear blue water and possible symbiotic relationships among organisms could allow it to thrive.

Scientists are puzzled about how the agaricia coral survive and thrive in deep water with such little light. Other coral reefs lie no deeper than 150 feet, but the Pulley Ridge reef sits below 250 to 275 feet of water, coral ecologist Wes Tunnell said. The 10-day research trip allowed some of the leading coral researchers to explore the relationships among coral, bioluminescent algae, red grouper and other creatures that call the reef home.

The iridescent multicolor coral called agaricia served as the main lure to Pulley Ridge. Scientists collected samples of the red, purple and blue lettuce-like coral and its neighboring green, leafy algae called anadyomene.

Living coral reefs are usually restricted to depths light can reach, which is why most are in shallow waters. At Pulley Ridge, the clear cobalt blue water and strong currents definitely lift some obstacles blocking the sun, but scientists wonder if it is enough.

The answer to Pulley Ridge's coral health could be tied to another symbiotic relationship, between the coral and a bioluminescent bacteria. Scientists discovered bacterial strains that glow in the dark and range in intensity and color from a neon green to greenish blue, said Kim Ritchie, manager of microbiology research at Mote Marine Laboratory in Sarasota, who likens the bacteria's properties to "superpowers."

Corals have never been shown to harbor bioluminescent bacterial symbionts. The glowing bacteria may help the coral access additional light. Ritchie speculates that the Pulley Ridge corals could also use the bioluminescence in the bacteria to attract zooplankton, a coral food source, she said.

[Last modified August 21, 2005, 00:50:20]


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