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Deep-Sea Expedition Begins

USC team to study some of Earth’s smallest organisms in some of the ocean’s darkest depths.

Deep-Sea Expedition Begins

Seldom has one scientist dived so deep to look at something so small.

For three weeks this month, USC College’s David Caron will join an expedition to study marine life around deep-sea hydrothermal vents. His specialty: protists, the single-celled organisms from which all complex life on earth evolved.

Caron, a professor in the Wrigley Institute for Environmental Studies at USC, belongs to a small band of marine biologists whose work is considered important enough to earn them a ticket on Alvin, the famous three-person submersible on loan to science from the U.S. Navy.

Caron and his colleagues, including several USC researchers and expedition leader Craig Cary of the University of Delaware, will sail aboard the research vessel Atlantis to two hydrothermal hot spots: Guaymas Basin in the Gulf of California and a group of vents in the eastern Pacific Ocean about nine degrees north of the equator.

Once above the vents, the researchers will take Alvin down from one to nearly two miles below the surface. Built to withstand crushing pressures and to pierce the utter blackness of the deep, Alvin will let the scientists observe life around the steaming vents and collect samples for analysis.

Caron will be studying an overlooked link in the deep-ocean food chain. Protozoa, a class of protists that feed on other organisms (unlike their vegetative cousins known as microalgae), may form a crucial bridge between bacteria and animal life.

If Caron is correct, the samples from the deep will show that protozoa feed on bacteria or on the products of bacterial activity and are in turn eaten by larger life forms.

The most surprising thing about the theory may be the lack of evidence for it. While other studies have found a protozoan-animal link in surface waters, the analogous middle step in the deep ocean has been overlooked.

“Protozoa are everywhere and they’re in virtually every environment. They play this intermediate food web role in a number of these environments, and there’s no reason to believe that they aren’t doing the same thing in the vents. It simply hasn’t been looked at to any degree,” Caron said.

According to study leader Cary, professor of marine biosciences at the University of Delaware, “For many years, the vents have been explored with little to no attention to viruses and protests. Yet because these organisms eat bacteria, they have the most dramatic effect on the bacterial communities that support the vent system. Our research programs are among the first to focus on these remarkable scavengers.”

The deep ocean is especially interesting due to the lack of plants, which depend on sunlight for photosynthesis. Instead, Caron said, bacteria around the vents create organic matter by transforming elements such as sulfur.

On a previous expedition, Caron’s group placed glass slides and an artificial mini-reef around the vents in order to collect protozoa. On this trip, the researchers will retrieve and analyze the samples.

Another goal of the expeditions is to chart the variation of ecologies at the base of the marine food web. The result has implications for climate change researchers, Caron said. If the base of the food web looks more or less the same around the oceans, then it would be less vulnerable to climate change. But if the ecologies at the base of the food web vary greatly between locations, then even small changes in climate could significantly affect ecosystem function.

The evidence so far is not conclusive on either side, Caron said.

The expedition sailed Nov. 10 and will return Dec. 1. High school and middle school students in classrooms across the country will be able to follow the researchers, submit questions, read blog entries, watch video and even place a “Phone Call to the Deep” through the expedition’s outreach portal at

“It is absolutely amazing to be on the bottom of the ocean,” Caron said. “I think probably the only thing you could liken it to would be to go up on the shuttle, and I’d do that at the drop of a hat.”

The USC research team includes Karla Heidelberg, assistant professor of biological sciences; postdoctoral researcher Pete Countway; graduate students Amy Coid and Diane Kim; technician Jamie Botelho; and documentarian and USC alumna Lauren Farrar.

Other researchers include scientists and graduate students from the University of Delaware, the University of Colorado, the University of North Carolina, the J. Craig Venter Institute, Universidad Nacional Autónoma de México and the University of Waikato, New Zealand.

The National Science Foundation funded the expedition.

For the blog "Daily Discoveries," visit