Student Research Takes a Dive ... to the Ocean Floor

Story posted October 28, 2009

submersible on crane
A large crane aboard ship lowers the submersible containing Will Hatleburg '11, Dan Thornhill, and pilots, into the Gulf of Mexico.

The panic lasted less than a minute.

Shortly after the crane lowered the small submersible from the deck of the research boat into the waters of the Gulf of Mexico, Will Hatleberg '11 forgot that he couldn't move more than a couple of inches in any direction. That he was pinned inside a vacuum-sealed vessel with his professor and two sea pilots—and several days' life support —slowly sinking to the bottom of the sea.

He watched in growing wonder as the darkening depths were illuminated by bioluminescent organisms that streamed past a small porthole "like snow going upward." Skates glided by. A squid released a jet of ink. Slowly, the light disappeared until they descended into total darkness.

Twenty minutes later, at about 1,500 feet, they hit bottom.

"It was a strange feeling of arrival," said Hatleberg. "It all came into vision suddenly. You could see about 40 feet around you from lights outside the submersible. It just snapped to."

What they saw was exactly what his professor, Dan Thornhill, was hoping for: a thicket of annelid tubeworms growing along the muddy ocean floor. The Bowdoin Doherty Marine Biology Postdoctoral Scholar had brought Hatleberg to this exact spot off the coast of Louisiana in search of a lowly worm.

The 10-day research trip, which was sponsored by the National Science Foundation, included Thornhill's research cohorts from Auburn University, two Bowdoin students, and 11 graduate and undergraduate Auburn students. View project Web site.

The team was there to collect samples of the rarely seen species, which is an ancient form of sea life that lives off energy completely unrelated to the sun.

The annelid tubeworm is unique in that it lacks a functional digestive system. Instead it receives nourishment produced by bacteria that exist symbiotically inside its storage organ. There, the bacteria convert toxic chemicals, such as hydrogen sulfide or methane, into life-sustaining sugars.

underwater creatures
The divers encountered a wide array of sea life, including (l. to r.) anemones and Blackbelly Rose Fish, a 15-inch pelagic salp, and clams among the annelid tubeworms.

Tubeworms are typically found at sites where there is significant geothermal energy, such as hydrothermal vents. However, this trip's discoveries brought the study of tubeworms into new territory.

"We were studying hydrocarbon seeps," explained Thornhill. "These are areas of the ocean floor where fossil fuels percolate up through the sediments. There are lots of oil rigs in this part of the Gulf that also extract these hydrocarbons. Complex microbiological reactions take place at these ecosystems that produce hydrogen sulfide, which the worms and bacteria then turn into a useable form of energy for life."

hatleberg and bell
In spite of several days of rough seas, both Hatleberg (l.) and Bell describe the voyage as one of the "best experience of my life."

In their six days at sea, various teams of researchers made four-hour dives in the submersible—usually two dives per day. Using sonar to navigate, the vessel sampled several sites along the ocean floor, collecting tubeworm colonies with cup-shaped equipment affixed to robotic arms.

Among the other creatures collected were sea stars, shrimp and crabs. While not their primary research focus, the biodiversity of this rarely studied ecosystem is of wide import to marine ecologists, noted Thornhill.

"There are a few fish at the bottom," he said, "but mostly it's expansive mud down there. In some places you can see methane bubbling up and mats of orange bacterial masses where clams and mussels can live. We saw a lot of shark eggs at one site."

sorting worms
Will Hatleberg '11 (r.) works with a student research colleague from Auburn University to sort tubeworm samples.

Once the bounty was brought topside, the rest of the team scrambled to sort, extract, and preserve the worm samples. Cutting through their fingernail-thick chitin tubes, the live worms had to be removed quickly in order to keep their DNA and RNA intact.

The purpose of the sampling is to try to understand the evolutionary biology of both tubeworm and its microbial flora—and to begin unraveling the genetic functioning of its symbiotic relationship.

"When you step back and think about it the worms are a little gross," noted Courtney "CJ" Bell '10, the other Bowdoin student researcher aboard. "But it was totally interesting and cool while we were doing it."

submersible reaches surface
Having just been lowered into the sea by a giant crane aboard ship, the submersible begins its 1,500-foot descent.

The best part, she said, was the moment when an incoming submersible would "bob like a cork to the surface."

"When it came up at night it looked like a crazy alien thing. You would see lights off in the distance—the big spotlights on front and a safety beacon on top to help the ship locate them. You would see those lingering under the surface."

The trip was a defining moment for both Bowdoin students.

Bell, a psychology major, is engaged in a yearlong independent study with Thornhill to locate communities of a related annelid that are believed to be colonizing on whale bones in the Gulf of Maine. "After having this great experience on the boat, it gives me more of a direction of where I want to go," she says. "Research really appeals to me."

Hatleberg, who spent the summer as a Doherty Fellow in Thornhill's lab, says his trip to the bottom of the sea fulfilled a lifelong dream: "When I was younger I watched a lot of nature shows and I always told my parents it was goal of mine to go to the bottom of the ocean.

thornhill and students
Thornhill (center) stands aboard the R/V Seward Johnson with Will Hatleberg '11 and Courtney Bell '10.

"The whole time on the trip I kept thinking how incredible it was, a once-in-a-lifetime opportunity that very few undergrads get a chance to do. I think it also says a lot about Bowdoin and what students can achieve if they want to. If you show interest, you can have some incredible experiences."

Hatleberg says he plans to continue the research as a honor's project, and hopes his work may contribute to publication.

"Both of these students were integral to the project," said Thornhill, "from dives, to sorting, to molecular work done onboard ship. Students so bright and hard-working are great ambassadors for Bowdoin."

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