Mote Marine Laboratory

Under Pressure

By: Nadine Slimak

When the call came for scientists to sample the United States’ deepest coral reef — newly discovered about 150 miles off Key West — Mote Marine Laboratory had just the team of technically trained divers needed to plunge more than 200 feet into the Gulf of Mexico. This was no dive for sissies.

On a hot July day more than 150 miles west of Key West, the Gulf of Mexico was smoother than a skillet, bluer than cobalt. Divers aboard the R/V Tiberon, a private research support vessel based in Key West, geared up. Tanks, hoses, booties, weights, masks, fins, semi-dry suits, hoods and more tanks.

Then the plunge; dropping for one minute, dropping for two, for three. All of a sudden, shallow water coral in a deep place where no one ever expected it. “Gorgeous. Just like a different world,” said dive team leader Jim Culter. “It’s like a two-dimensional coral reef because it’s so low and compact — like a grassland or prairie. There are oranges and yellows and electric-looking colors. It’s really exhilarating being the first divers.”

At the surface, humans are always under pressure — 14.7 pounds per square inch, to be exact. But 215 feet below the water’s surface, 111 pounds push down on every square inch of a diver’s body. At that depth, certain things — like breathing — are complicated.

“Oxygen gets to be toxic,” said Culter, Mote senior scientist and benthic ecologist who led the first team of scientific divers to ever explore Pulley Ridge. The dives were part of a multi-agency expedition to gather samples of species living on what the U.S. Geological Survey determined in December 2004 is the deepest reef populated with shallow-water corals ever discovered in the waters of the continental U.S.

While USGS had been surveying Pulley Ridge to discover its makeup since 1999 using remotely operated vehicles equipped with cameras and scientists seated in one-person mini-subs, Culter and his crew of nine technically trained divers had probably the most sophisticated viewing and sample-gathering devices of all: Their eyes and their hands. “They have a dexterity underwater that you just don’t have in the sub,” said oceanographer Dr. Sylvia Earle, who spent hours exploring the reef from a mini-sub during the expedition.

Gearing up for such dives is complicated. Because gases — such as oxygen — can become toxic at extreme depths, divers have special gas mixes that enable them to dive deep. They also have redundant systems — multiple tanks, multiple regulators, multiple safety devices — in case anything goes wrong. “There is a level of risk that could be severe,” Culter says. “Small problems become big problems.”

Such dives depend as much on years of training and hundreds of hours of experience as they do on the right equipment. Culter found his team members in a group of recreational divers who commonly put themselves through the rigors of complicated dives just for the fun of it. “We’re doing our part for science and we get to explore a place that’s never been explored before,” said diver Rusty Farst.

And, oh, what a place it is.

Some 12,000 to 14,000 years ago, Pulley Ridge was a barrier island that drowned in the last melting of the ice age. The 125-mile- long ridge sits at the western edge of the Loop Current, which brings warm, clear water and nutrients north into the Gulf of Mexico. It’s perhaps this loop that has helped shallow-water corals survive and thrive in such deep water.

Hermatypic, or reef-building, corals are usually only found in temperate, clear, shallow waters up to about 150 feet deep. Corals, which are animals made of polyps like sea anemones, secrete the calcium carbonate that makes up the reef. They live in symbiosis with zooxanthellae (zoh-zan-THEL-ee), tiny single-celled algae-like organisms that live in the polyp tissues, taking in light and emitting oxygen and energy that helps the corals produce calcium carbonate.

The zooxanthellae depend on light for survival, so Pulley Ridge — which gets very little sunlight because of its depth — really is a miracle when it comes to coral reef type and location, says Dr. Robert Halley, leader of the USGS team that confirmed Pulley Ridge was the deepest coral reef. “We’ve documented the southern end of the reef as coral rich areas and we’re trying to place that in a regional context. Are there more of them like it in the world? It’s a big ocean. “We’re just beginning to get a picture of what’s down there. We know a fair amount of reefs in shallow water have been declining in the last couple of decades because of coral disease. There’s no disease here.”

That might be because of the reef’s location so far offshore, said Billy Causey, superintendent of the Florida Keys National Marine Sanctuary, which helped underwrite the expedition. The ridge, located about 40 miles outside sanctuary boundaries, is farther away from man-created problems that plague inshore reefs. “We’re further away from the anthropogenic effects,” he said. “When these reefs start bleaching out here, then we’re really in trouble.”

Pulley Ridge could also be a place for fish to hide out before moving to shallower reefs closer to shore. Scientists have documented that the reef is peppered by burrow-building tile fish and other fish species that construct mounds. These structures in turn help attract other species. “Can these be refugia for species to resupply shallow reefs?” Halley asked. Perhaps. One researcher, Dr. Felicia Coleman from Florida State University has found what are believed to be spawning aggregations of red grouper using the burrows, Halley said.

The ridge is also unique in the types of fish species that inhabit it. Deep water species like deepwater squirrelfish (Sargocentron bullisi), bank butterfly fish (Chaetodon aya), and spotfin hogfish (Bodianus pulchellus) live alongside fish more common to  shallow reefs such as French angelfish (Pomacanthus paru), bicolor damselfish (Stegastes partitus) and hogfish (Lachnolaimus maximus).

For the scientists — and the divers recruited into scientific service — the 2005 Pulley Ridge expedition was the chance of a lifetime. “Ever since I’ve heard of Pulley Ridge, I’ve really wanted to see it for myself — even it’s only from an ROV (remotely operated vehicle),” said G.P. Schmahl, manager of the Flower Garden Banks National Marine Sanctuary in Texas.

Schmahl got his wish. He spent an hour or so underwater in Deep Worker, the mini-sub lent to the mission by Deep Marine Technology, based in Houston, Texas. “Being in the sub is just cool,” he said after returning topside to see the funny-looking creature one of the divers had placed in the sub’s collection basket. “I saw several of these as I was cruising by. They just looked like black lumps, so I’m glad someone put it in there.”

The black lump turned out to be a big slippery mollusk called a nudibranch, or sea slug — quite likely a species that had never been documented before.

In fact, many of the animals at Pulley Ridge — like the rows of polychaete worms swaying in the current there — have probably never been seen before. And scientists have only begun to explore its mysteries and learn about the creatures that live there. “Pulley Ridge was unexplored for all of human-kind’s history,” Earle says. “It wasn’t until recently that we’ve even had the technology to get deeper than 100 feet. I haven’t seen anything like this anywhere in the world.”

Coming from a woman who has dived all over the world, from a woman who holds records for deep dives, that’s saying a lot.

Miracle Expedition

Scientists on the June 22 to July 2, 2005 expedition to explore Pulley Ridge have dubbed it the “miracle expedition on the miracle reef.”

One reason was the technology that came together during the exploration: divers, remotely operated vehicles, mini-subs and sophisticated mapping equipment. Another was the number of agencies that participated.

Dr. Wes Tunnell of the Harte Research Institute for Gulf of Mexico Studies and Sylvia Earle hatched the idea to explore Pulley Ridge. “Then we started e-mailing colleagues,” Tunnell said.  Armed with $50,000 from the institute, the pair sent word out to others they thought might join the expedition.

The Florida Department of Environmental Protection and the Florida Keys National Marine Sanctuary provided additional funding. In-kind financing and scientific experts for the expedition came from the U.S. Geological Survey, Mote Marine Laboratory, the Florida Institute of Oceanography, the University of South Florida College of Marine Sciences, the Florida Fish and Wildlife Research Institute and Earle’s company, Deep Ocean Exploration and Research.

“This was a very focused effort on the part of a half-dozen agencies,” says the USGS’ Robert Halley, the expedition’s chief scientist. “It’s very unusual because the natural tendency is for people to do their own thing. This was a miracle cruise.”

On Topic: A Conversation with Dr. Sylvia Earle

Sylvia Earle wears so many sets of flippers it’s hard to keep track of her comings and goings. Among her many endeavors, Earle is a former director at Mote Marine Laboratory and still serves on the lab’s board of trustees. Earle is also a member of the board of the newly endowed Harte Research Institute for Gulf of Mexico Studies at Texas A&M University-Corpus Christi, chairman of Deep Ocean Exploration and Research, director of Global Marine Programs for Conservation International and Explorer-in-Residence for the National Geographic Society.

There is one job Earle holds above others: “My main job is to explore the oceans and that’s exactly what we’re doing here,” she says aboard the R/V Suncoaster, base of mini-sub operations on Pulley Ridge. After decades of exploration, Earle has some definite opinions on ocean science, conservation and man’s role as ocean protector.  Here is a snapshot of some of those views. For more, see a MoteTV video clip at www.mote.org/motetv.

On ocean education:  “These days, in the 21st Century, with our communication systems being what they are, no one is really isolated from knowledge about what’s happening anywhere else in the world. We have the technology to be able to share the understanding (of oceans) with everybody. It really should start as basic as learning your A-B-Cs and your 1-2-3s that we’re dependent on the natural world; we’re dependent on the oceans for every breath we take and for every drop of water we drink.”

On funding for ocean science:  “I wouldn’t take a thing away from what we’re doing with space exploration and I applaud it, I support it and I really think we ought to do more in that direction. But we should have an equal commitment to exploring this part of space — this aquatic planet that does happen to be the only place that we know in the universe that’s suitable for 6 billion people.”

On the U.S. Ocean Commission report to Congress:  “I’m encouraged by the fact that there is an ocean commission — the first time in decades that a national committee has been appointed to really take an overview of the ocean and its relevance back to human beings to find out what we’re doing to the oceans, what the nature of the ocean is, to really assess where we are at this point in time.”

On recommendations made by three key ocean reports:  “Curiously, these three committees as well as other committees and other meetings around the world have convergence. The common sense appraisal of what’s happening to the oceans focuses on a number of issues. We’re taking too much wildlife out of the oceans and we’re doing it with techniques that are too disruptive. All of these arrows are pointing to the idea that we have to get serious about exploring the ocean and we have to get serious about governance.”

Deep-Reef Lighting

One of the coolest things that researchers found on the Pulley Ridge expedition was glow-in-the-dark coral bacteria.

“We were going through all this stuff on the boat” — after dark and by the light of a flashlight — “when we saw a little pinpoint of green neon glow,” said Dr. Kim Ritchie, whose job on the expedition was to sort samples taken at the ridge for 26 different researchers. “We finally pinpointed it. I have to credit Jim (Culter). He spotted it.”

It was when Ritchie cultured the bacteria in the lab as part of her ongoing studies into coral microbiology that she found them glowing. “I did all these fancy bioassays to find antibiotics, and all I had to do was turn off the lights. It was so exciting.”

The bacteria were so bright that when Ritchie shut the lights in her lab off, the corner of the room where the Petri dishes were stacked glowed. “It was pretty eerie.”

Why would Pulley Ridge corals have glow-in-the-dark properties? “You find bioluminescence in organisms living in the water column — like in angler fish and squid,” Ritchie said. “The deeper you go, you find more bioluminescence. To grow there, you need to make your own light. Why would corals have it? Maybe it helps them catch plankton but we’re still trying to determine its significance.”

Learn more about: Coral Reef Research

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