NOAA 2000-514
Contact: Jana Goldman


People do not usually think of corals in the same way that they think of sharks, but both are predators. While sharks chase large prey, corals wait in the watery darkness of night and prey on nearly microscopic zooplankton that drift by, or swim too close. The sixth of ten planned research missions conducted using NOAA's underwater laboratory will document exactly how corals feed, and what they eat.

A team of scientists led by Drs. Ken Sebens and Karla Heidelberg, both of the University of Maryland, will spend ten days fifty feet underwater in Aquarius, the nation's only underwater laboratory. They will be collaborating with Drs. John Bythell and Jeremy Thompson of the University of Newcastle, England.

"Interestingly, corals feed primarily at night because that's when more zooplankton are in the water," said Dr. Steven Miller, director of the National Undersea Research Center that manages Aquarius. "But corals are attached to the bottom by their hard skeletons, so how do they hunt? Corals have tentacles that are armed with tiny, poisonous stinging cells, that can be discharged into prey that happen to float or swim into range. The special stinging cells help to immobilize and hold the prey, until transfer into the coral mouth."

The research team will document this hidden world of coral feeding biology using high-resolution infrared video cameras and specially designed sampling devices. The aquanauts will spend considerable time on the reef at night, setting up experiments and
collecting data.

The aquanauts will also study how water motion affects coral feeding and growth. Even at short distances, the rate of flow over and around corals can change dramatically. This is significant because water motion has large impacts on coral biology, affecting processes such as growth, competition, larval dispersal, fragmentation, and sedimentation, Miller said. Water motion also delivers prey to corals and enhances the uptake and exchange of nutrients, oxygen, and carbon dioxide. The aquanaut team will deploy sophisticated equipment to measure current speed and direction at the site, as well as flow over and around individual corals.

After the aquanauts spend time diving on the reef each day—dives that average between three and four hours are common—they swim back to their underwater home and laboratory. Hot food, warm bunks, Internet access, and sophisticated equipment are all immediately at hand inside Aquarius. Living quarters are tight, and resemble a high-tech motor home in terms of size and comfort.

Aquarius is the world's only undersea laboratory dedicated to science, and is operated by the University of North Carolina at Wilmington for NOAA. The underwater lab is 3.5 miles offshore near Key Largo, in the Florida Keys National Marine Sanctuary. Aquarius provides computers, power and the necessary bottom time that allows the scientists, or aquanauts, to conduct their studies directly on the reef - day and night.

During this mission, Mike Hutchens and Thor Dunmire are the UNCW onboard specialists who run Aquarius from inside. Hutchens and Dunmire are supported by a highly trained shore-based team who work from Mission Control, ten miles away in Key Largo.

This month, ocean data (underwater temperature, salinity, and current speed and direction) will be posted live on the Internet at UNCW's Aquarius Web site, along with Web cameras inside and outside Aquarius, expedition journals from the aquanauts, and detailed project information.

Information collected during this Aquarius mission is related to understanding the distribution and abundance of corals on reefs, especially in Florida where substantial human impacts occur and significant natural system variation in water quality frequently occurs.