July 13, 2014

NC State, Duke University team up to explore the deep sea

NC State and Duke University scientists plunged more than 3,500 feet in the submarine Alvin to investigate the underwater communities that thrive among methane gas bubbles and seeping hydrogen sulfide.

Scientists plunged more than 3,500 feet in the submarine Alvin to investigate the underwater communities that thrive among methane gas bubbles and seeping hydrogen sulfide. Activated floodlights revealed the mysterious creatures living in one of the most extreme environments on Earth – cold seeps.

As scientists peered through a tiny porthole to the ocean’s abyss, they wondered: How did these animals get here?

In May and June, researchers at N.C. State, Duke University and the University of Oregon ventured out into the Gulf of Mexico on the R/V Atlantis, the 142-foot research vessel home to the deep-sea submersible Alvin. The three universities banded together – each equipped with a unique skill set – on a mission to understand the interconnectedness of cold-seep communities there, Barbados and off North Carolina.

Cold-seep communities differ from the much hotter and less common hydrothermal vents. Cold seeps have a typical deep-sea temperature of 35 to 39 degrees Fahrenheit and leak gases from the seafloor. Hydrogen sulfide and methane ooze and bubble, providing chemical food to bacteria that live in the sediment and inside the guts of animals such as worms and clams.

Cold seeps have evolved under such extreme environmental and chemical conditions that scientists predict they may be candidate sites for bio-prospecting for anti-cancer agents or other pharmaceuticals.

Cold seeps are scattered like islands across the ocean floor. They appear disconnected, but ocean currents carry larval spawn to seeps near and far. Even though seeps are some of the most abundant and large geologic features in the planet, scientists are just beginning to understand how these communities are colonized.

Scientific partnering

Researchers from the three universities partnered to study cold-seep communities as part of a multiyear project funded by the National Science Foundation.

“It was like getting the A-team together,” said Cindy Van Dover, the lead scientist on the project. She’s a biology professor and director of the Duke University Marine Lab.

David Eggleston, N.C. State biologist and director of the Center for Marine Sciences and Technology, and N.C. State physical oceanographer Roy He brought expertise on the movement of marine larvae and ocean currents.

“We use observation and numerical models to predict larval transport,” explained He.

Duke University scientists offered genetic tools to identify the relatedness of populations. University of Oregon larval biologists provided the skills to spawn animals on board and for rearing their larval offspring, which are still living and being studied today.

The collaboration allows scientists to compare results and synthesize their information to form a more holistic study of cold-seep communities.

N.C. State graduate student Doreen McVeigh is building a particle-tracking model to simulate the movement of larvae. Her model combines He’s measurements of ocean currents with larval behavior. She is comparing her model predictions to genetic information to see whether they match up. These tools reveal whether cold-seep “island” populations are isolated or connected.

During meals and library meetings, scientists problem-solved challenges and brainstormed how to maximize their collections, all agreeing that these conversations inspired new hypotheses and solved puzzles.

“By being on ship at the same time, we were able to initiate a really exciting project that could bear fruit,” said Craig Young a professor of biology at the University of Oregon.

Next summer the research team will travel to its final collection sites off North Carolina, adding to data collected in Barbados during the summer of 2013 in the Gulf of Mexico last month.

“We are all really eager to see the synthesis paper that comes out of this. … The real big picture has yet to come, and that’s going to be super exciting,” said Van Dover.

A day at sea

Scientists deployed larval traps, plankton nets, hydrophones and even train wheels to collect their data. The most advanced technology on ship were the submarine Alvin and the unmanned remote-operating vehicle Sentry. Sentry used sonar to map the seafloor and target areas for Alvin to explore.

“This was a tremendous asset,” said Eggleston. “We can have maps in hand before going down in the submarine.”

Guided by Sentry’s map, Eggleston directed Alvin to a deep-sea brine lake surrounded by mussels, a location not seen since the late 1990s. The close proximity to the brine pool of mussels suggests that they are consuming bacteria seeping from the pool, an exciting find for the scientists. Alvin’s large robotic arm collected specimens and captured video footage of the seafloor teeming with mussel beds, 150-year-old tube worm forests, bizarre fish and a type of sea cucumber called the headless deep-sea chicken. Calm seas enabled Alvin to complete all of its scheduled dives, giving more students the opportunity to direct an expedition.

“Every time one of these students came up, they had big old grins on their faces. It’s just the best thing in the world to share that environment,” Van Dover said.

After Eggleston completed his first Alvin dive, he was greeted on deck by a game-winning water cooler shower, his initiation as a deep-sea explorer.

Scientists collect animals at different times and depths to determine whether floating larvae find new habitat using surface or bottom currents, which typically flow in opposite directions and at different speeds. N.C. State scientists collected and deployed large moorings equipped with time-release larval traps, current meters and sound-recording hydrophones. These hydrophones recorded the sounds of deep-sea life for the first time. Traveling larvae may use sound to find the right habitat to live.

In the ship’s laboratory, scientists identified specimens, studied their behavior and preserved samples for genetic analysis.

“By studying how these organisms are adapted to extreme environments,” Van Dover said, “we can learn a lot about the diversity of life.”

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