Age of Aquarius: Undersea lab immersed in coral reef research

July 24, 2000
Web posted at: 3:56 p.m. EDT (1956 GMT)

By Environmental News Network staff

They lived on the ocean floor for 10 days straight.

"You never see the sun and you never completely dry out," explained Karla Heidelberg, a lead scientist from the celebrated Aquarius mission that ended this week.

Operated by the University of North Carolina at Wilmington, Aquarius is the world's only undersea laboratory dedicated to science. Positioned near Key Largo in the Florida Keys National Marine Sanctuary, the lab is allowing scientists to monitor more closely and comprehensively life at the bottom of the sea.

With their base of operations set snugly on the ocean floor, researchers can dive for up to nine hours at a time. Surface dives, by comparison, usually last between one to two hours.

Aquarius researchers, or "aquanauts," conducted studies day and night, directly on coral reefs. For the first time, they evaluated all aspects of coral feeding in their natural habitat.

Prior to the Aquarius project, most research on coral reef diet was conducted in a laboratory "under unnatural conditions," Heidelberg said.

At least 30 different species of coral were examined on the Aquarius mission. In addition to filming coral feeding throughout the night, the aquanauts examined zooplankton abundance at multiple heights off the reef bottom to determine available prey. They also were able to characterize the fine-scale patterns of water flow around coral colonies.

Experiments such as this coral feeding flume require continuous power for data transmission, supplied by cable from the Aquarius vessel

Even at short distances, the rate of water flow over and around corals can change dramatically. This is significant because water motion plays a big role on coral biology, growth, competition, larval dispersal, fragmentation and sedimentation. Water motion also delivers prey to corals and enhances the exchange of nutrients, oxygen, and carbon dioxide.

"We focused on the basic biology of coral reefs, Heidelberg explained. "First we wanted to find out how many nutrients are available to the coral. Next, we wanted to see how the interaction between zooplankton and coral works.

"Coral reefs are unique systems that we know relatively little about. Ironically, scientists and legislatures are being asked to develop management guidelines to preserve these rapidly changing ecosystems before we fully understand the basic biology of reef ecosystems. As we learn more about the biology of the reefs, we will be better able to develop management guidelines that will protect our reefs."

The greatest impact of human activities on coral reefs are added nutrients caused by fertilizer, non-point source pollution, sedimentation from coastal development, forest destruction and sewage runoff from land, Heidelberg noted.

"Nutrients cause large algae blooms and increased particulate matter in the water column," she explained. "The added particulates filter out needed sunlight to the bottom and also clog coral feeding structures. The coral has to expend excess energy to remove the particles and consequently may have more difficulty feeding on zooplankton."

Coral reefs in the Florida Keys are particularly sensitive because of their location, Heidelberg said. "Florida reefs are at the northernmost extreme of where they can survive before the water gets too cold. Adding more stress could be enough to shift the ecosystem."

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Aquarius mission web site
Florida Keys National Marine Sanctuary

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