Editor’s note: This is the second in a series of articles called Working Conditions, about the unusual work environments in which some University of Hawaiʻi faculty conduct their research.

Investigating nutrient cycling by sponges. Photo courtesy NOAA and UNC Wilmington

Marine biogeochemist Brian Popp recently found himself 65 feet deep on a colorful reef off the coast of Florida.

Not too unusual for a fellow who studies marine sponges, among other things… except for the fact that he remained underwater for 10 days.

The 52 year-old researcher, a professor at the University of Hawaiʻi at Mānoa’s School of Ocean and Earth Science and Technology since 1990, was one of the lucky few awarded a stay as an aquanaut aboard the world’s only undersea research laboratory.

While there are other underwater habitats around the globe, Aquarius is the only one solely dedicated to scientific research. Owned by the National Oceanic and Atmospheric Administration and operated by the University of North Carolina at Wilmington, Aquarius lies approximately four miles off Key Largo, Fla.

Aquanauts called the underwater habitat home for 10 days. Photo courtesy NOAA and UNC Wilmington

Aboard Aquarius, four researchers and two support technicians eat, sleep and perform all the functions of daily life in a structure about the size of a school bus.

“School kids always want to know if we have a bathroom,” says Popp, blue eyes twinkling. “We do.” The habitat also has a hot shower, six bunks and a kitchenette where freeze-dried meals are prepared.

Why live underwater relatively close to shore? Earth’s air is mostly nitrogen, about 80 percent, and only about 20 percent oxygen. SCUBA divers using air tanks operate under strict safety guidelines—the deeper the dive, the shorter its duration—because the buildup of nitrogen in the diver’s body causes decompression sickness if a diver resurfaces too quickly.

There is a point at which the diver’s body is saturated, meaning no more nitrogen can be absorbed, allowing the diver to remain submerged for days on end.

Aquanauts must decompress for 18 hours to remove the nitrogen from their bodies before resurfacing, but being free from constraints of conventional SCUBA diving protocols maximizes research time and minimizes logistical complications, Popp says.

After 10 days underwater, aquanauts must decompress for 18 hours before resurfacing

Using Aquarius as a base, the crew spent up to six hours doing research on surrounding Conch Reef, returning to replenish their SCUBA tanks and talk to each other in an air-filled gazebo. (While diving, the researchers have no verbal communication and rely on hand gestures and writing notes to each other on underwater slates.)

“It means being able to work, uninterrupted, for six hours,” he says. “Six hours might seem like a long time, but when you’re down there, it doesn’t seem nearly long enough.”

On his most recent mission in October 2008, Popp closely monitored the chemistry of barrel sponges and explored their importance in reef ecology.

“We were very surprised to find that they play a significant role in nutrient cycling,” he says. Sponges are porous, they host numerous bacteria and they pump a lot of seawater,” he explains.

With University of North Carolina colleagues Christopher Martens and Niels Lindquist and UH graduate student Christina Bradley, he was able to accurately measure just how effective a filter even a moderately-sized sponge can be.

Popp points to a photograph of a sponge so festooned with instrumentation, including an underwater mass spectrometer, that it resembles Star Wars robot R2D2. “A sponge that’s only 2 feet tall can filter the seawater equivalent of an Olympic-sized swimming pool in less than five days,” he exclaims.

Such findings, published only within the past five years, have tremendous implications with respect to the health of reefs worldwide, particularly in a changing global climate, he adds.

“The taxpayers are paying for this and I’d like to think that our work helps maintain the health of coral reefs in the future.”

Watch fluorescent dye flow through a sponge.

The mission also supports community outreach education. Popp used the live, 24-hour video stream feed on the Aquarius website to illustrate a presentation to daughter Nicole’s Lanikai Elementary class in October, talking remotely via cellular phone set on speaker by his wife, private sector geologist Jan Reichelderfer.

Popp may make his fourth, and possibly last, saturation mission as an Aquarius aquanaut this year. Meanwhile, he promotes opportunities for younger researchers to take advantage of the habitat’s unique and limited research capability.

“After all,” he says, “they are the next wave.”

Read more about Aquarius or view the photo galery.

Tags: marine biology, School of Ocean and Earth Science and Technology, UH Manoa, Vol. 34 No. 1, Working Conditions