By Denise Brehm
Civil & Environmental Engineering

The National Academy of Sciences (NAS) awarded Professor Sallie W. (Penny) Chisholm the Alexander Agassiz Medal for original contribution in the science of oceanography, at a ceremony in Washington, D.C., April 25.

Chisholm, the Lee and Geraldine Martin Professor of Environmental Studies in the Department of Civil and Environmental Engineering and the Department of Biology, was chosen for her “pioneering studies of the dominant photosynthetic organisms in the sea and for integrating her results into a new understanding of the global ocean.”

She was a member of the team of scientists from the Woods Hole Oceanographic Institution and Harvard that in 1986 discovered Prochlorococcus, a photosynthetic marine microbe that Chisholm has since developed into a model organism that can be studied from the molecular to the global level. Thanks to the research of Chisholm and others, we now know that these are the smallest and most abundant photosynthetic cells in the oceans, often accounting for as much as half of the oxygen production in some regions of the sea.

In announcing its selection, the NAS award committee said: “Dr. Chisholm is an outstanding biological oceanographer whose studies have revolutionized our views of photosynthesis in the ocean. In particular, her use of flow cytometry (a technique for electronically counting and examining microscopic particles in a stream of fluid) has led her and her colleagues to the discovery that small plankton (in particular Prochlorococcus) account for a much more substantial part of marine productivity than had previously been realized.

“Since the discovery of Prochlorococcus in 1986, Dr. Chisholm has used other modern techniques to examine its genetic structure, its life cycle, the viruses that attack it and its dominant role in the marine biosphere. She has shown a remarkable ability to integrate detailed biological studies at the molecular scale with insightful analyses of the world’s oceans,” the committee’s announcement said.

Chisholm is the 46th recipient of the Agassiz Medal. She recently met His Highness Prince Albert II of Monaco, the great-great-grandson of the second Agassiz Medal winner, when he visited MIT April 13 to discuss his film, “Antarctica 2009: A Continent in a State of Alert.” Albert I was one of the founders of oceanography; he received the Agassiz Medal in 1918.

The award is named after Alexander Agassiz, an American marine scientist who earned his fortune through his investment in a copper mine near Calumet, Mich., in the Upper Peninsula where Chisholm’s hometown, Marquette, is located.

Chisholm joined the MIT faculty in 1976. She was director of the MIT Earth System Initiative from 2002-2008 and MIT director of the MIT/Woods Hole Joint Program in Oceanography and Oceanographic Engineering from 1988-1995. She is recipient of many awards and honors, including the Huntsman Award for Excellence in Marine Science (2005) and the Rosenstiel Award in Ocean Sciences (1991). She has been a resident scholar at the Bellagio Conference and Study Center in Italy (1998) and a Guggenheim Fellow (1997). She was elected to the NAS in 2003, the American Geophysical Union in 1996, and the American Academy of Microbiology in 1993.  She co-authored a children’s book about photosynthesis with Molly Bang, “Living Sunlight: How Plants Bring the Earth to Life.”