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In Search of Vent Protists
The USC research team includes, from left, Amy Koid, Diane Kim, Dave Caron, Jamie Botelho, Karla Heidelberg, and Pete Countway.
Seldom has a scientist dived so deep to look at something so small.
David Caron, a professor in the Wrigley Institute for Environmental Studies at the University of Southern California (USC), is leading the Extreme 2008 research team that is focusing on protists, the single-celled organisms from which all complex life on Earth evolved.
He and his colleagues, including several USC researchers and expedition chief scientist Craig Cary of the University of Delaware, are 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 Dr. 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,” Dr. Caron says. “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,” he notes.
On a previous expedition, Dr. 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.
The Caron team observed protozoa--ciliates--similar to this
shallow-water Euplotes species at the vents in 2007. Click to view a movie.
Another goal of the team is to chart the variation of ecologies at the base of the marine food web. The result has implications for climate change researchers, Dr. Caron says. 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, Dr. Caron notes.
The USC research team includes Drs. Karla Heidelberg, assistant professor of biological sciences and Pete Countway, postdoctoral researcher; graduate students Amy Koid and Diane Kim; technician Jamie Botelho; and documentarian and USC alumna Lauren Farrar.
Adapted from an article by Carl Marziali, USC Public Relations.
This 3-D image shows an amoeba with pseudopods engulfing its food. Courtesy of Kirk Czymmek, Delaware Biotechnology Institute Bio-Imaging Center, University of Delaware.
The word "Protista," or "protists," means "the first ones." Protists include a rich diversity of tiny single-celled organisms from slime molds to protozoa, the latter of which are the focus of the Extreme 2008 protist team.
The word "protozoa" means "first animals." These tiny organisms come in a diversity of shapes, sizes, and methods of feeding and moving.
Hair-like cilia propel some protozoa through the water, while whip-like flagella move others along.
In marine and freshwater systems, protozoa play important roles in the food chain because they feed on the vital first link -- bacteria, archaea, and microalgae. This grazing activity by protozoa not only controls populations of other microbes but also helps to return nutrients back into the environment for reuse. Some protists have even evolved symbiotic and parasitic relationships with other organisms of their kind and with higher-order life forms.
To learn more, visit
Dr. Caron's Protists Web page!
