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The Invisible Forest: Microbes in the Sea

Sallie (Penny) Chisholm: November 15, 2006; Running Time: 1:00:35

About the Lecture

About the Lecture

After listening to Penny Chisholm, you’ll view pond scum or aquarium slime in a different light. In fact, Chisholm aims to instill a sense of reverence and concern for the organisms behind this phenomenon, which turn out to be blue-green algae. They’re part of a family of microbes called phytoplanktons that are essential to the earth’s health.

Chisholm sketches the history of phytoplanktons, which first emerged on earth 3.5 billion years ago, and created the oxygen in our atmosphere that made possible all other plant and animal life. “They can live perfectly well without us,” says Chisholm, “but we can’t live without them.” Energized by sunlight, phytoplankton are the ultimate recyclers. Chisholm’s research focus, Prochlorococcus, discovered in 1985, plays a supremely important role in climate control. The smallest and most abundant photosynthetic cell on the planet, it takes carbon from the atmosphere and deposits it safely to the ocean floor.

We must stop viewing all microbes as bad guys, Chisholm says, and instead, start to worry about the collective health of the organisms that regulate the world’s metabolism. Those hard at work clearing our air of global warming gases may not fare so well as the earth heats up. When ocean temperatures rise, Chisholm says, waters get more stratified, and this may make photosynthesis more difficult for the microbes. There are proposed attempts to manipulate or work around phytoplanktons – such as ocean fertilization or deep-sea injection of CO2 – but Chisholm is deeply skeptical. We may end up sucking oxygen out of the water and creating dead zones in the ocean “that release methane, nitrous oxide and other wonderful greenhouse gases that molecule for molecule, prove more powerful than CO2 in absorbing solar energy,” she warns.

Science has only just begun to study the world’s microorganisms. Just .1% of all microbes have been cultured, and who knows what other kinds of unique and essential properties we’ll find when we start looking, says Chisholm. It’s time we begin “to build the knowledge necessary to predict, regulate and sustain these vital functions of earth systems for future generations,” she says.

Lecture Details

Location: Hotel@MIT

“Biomedicine has done amazing things for human health. Now we need to focus on planetary health. ...It’s preventive medicine for the earth, basically. The challenge is orders of magnitude greater.”

Penny Chisholm

About the Speaker

Sallie (Penny) Chisholm

Professor of Civil and Environmental Engineering and Biology;
Lee and Geraldine Martin Professor of Environmental Studies
Director, MIT Earth System Initiative

In addition to her other appointments, Penny Chisholm currently serves as co-director of Terrascope, an MIT learning community for freshmen. She is also a visiting scientist at the Woods Hole Oceanographic Institution. From 1988-1995, she served as the MIT Director of the MIT/Woods Hole Joint Program in Oceanography.

Chisholm received the 2005 Huntsman Award for Excellence in Marine Science, and is a Gordon and Betty Moore Foundation Investigator in Marine Science. She has published papers in PNAS and Nature. She received her Ph.D. in Biology in 1974 from S.U.N.Y. Albany.

Sallie (Penny) Chisholm

Chisholm's Biology website

About the Host

About the Host

MIT Museum

Cutting-edge technologies, amazing holograms, and the beauty of Harold Edgerton's strobe photography entertain, educate, and enlighten at the MIT Museum. Robotics, underwater exploration, kinetic sculptures, and the variety of interactive programs and historic collections attract visitors and researchers from around the world. This unique museum recently opened the Mark Epstein Innovation Gallery featuring some of the latest work of selected research groups at MIT.