Sallie Watson "Penny" Chisholm (born 1947) is an American biological oceanographer at the Massachusetts Institute of Technology. She is an expert in the ecology and evolution of ocean microbes. Her research focuses particularly on the most abundant marine phytoplankton, Prochlorococcus, that she discovered in the 1980s with Rob Olson and other collaborators.[1] She has a TED talk about their discovery and importance called "The tiny creature that secretly powers the planet".[2]
Chisholm has been a faculty member at the Massachusetts Institute of Technology since 1976 and a visiting scientist at the Woods Hole Oceanographic Institution since 1978. Her research has focused on the ecology of marine phytoplankton.[4] Chisholm's early work focused on the processes by which such plankton take up nutrients and the manner in which this affects their life cycle on diurnal time scales. This led her to begin using flow cytometry which can be used to measure the properties of individual cells.
The application of flow cytometry to environmental samples led Chisholm and her collaborators (most notably Rob Olson and Heidi Sosik) to the discovery that small plankton (in particular Prochlorococcus and Synechococcus) accounted for a much more substantial part of marine productivity than had previously been realized. Previously, biological oceanographers had focused on silicaceous diatoms as being the most important phytoplankton, accounting for 10–20 gigatons of carbon uptake each year. Chisholm's work showed that an even larger amount of carbon was cycled through these small algae, which may also play an important role in the global nitrogen cycle.
In 1994, Chisholm was one of 16 women faculty in the School of Science at MIT who drafted and co-signed a letter to the then-Dean of Science (now Chancellor of Berkeley) Robert Birgeneau, which started a campaign to highlight and challenge gender discrimination at MIT.[6]
In January 2010, she was awarded the Alexander Agassiz Medal, for "pioneering studies of the dominant photosynthetic organisms in the sea and for integrating her results into a new understanding of the global ocean."[7]
In 2013, she was awarded the Ramon Margalef Prize in Ecology, "for being one of the most productive, charismatic and active researchers on biology and marine ecology".[8]
On May 24, 2018, she was awarded the Doctor of Science degree by Harvard University.[9]
In 2019 she received the Crafoord Prize in Biosciences, "for the discovery and pioneering studies of the most abundant photosynthesising organism on Earth, Prochlorococcus".[10] This prize is considered equivalent to the Nobel Prize (for which there is no Biosciences category). Chisholm was honored at the Crafoord Prize Symposium in Biosciences[11] at which 6 internationally prominent scientists spoke (in order of presentations): Alexandra Worden (GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany), Corina Brussaard (NIOZ Royal Netherlands Institute for Sea Research, The Netherlands), Ramunas Stepanauskas (Bigelow Laboratory for Ocean Sciences, US), Rachel Foster (Stockholm University, Sweden), Francis M. Martin (INRA French National Institute for Agricultural Research, France) and David Karl (University of Hawaii, US).
Lindell, D.; Jaffe, J.D.; Coleman, M.L.; Axmann, I.M.; Rector, T.; Kettler, G.; Sullivan, M.B.; Steen, R.; Hess, W.R.; Church, G.M.; Chisholm, S. W. (2007). "Genome-wide expression dynamics of a marine virus and host reveal features of coevolution". Nature. 449 (7158): 83–86. Bibcode:2007Natur.449...83L. doi:10.1038/nature06130. PMID17805294. S2CID4412265.
Chisholm, Sallie W.; Falkowski, Paul G.; Cullen, John J. (October 12, 2001). "Dis-Crediting Ocean Fertilization". Science. 294 (5541). American Association for the Advancement of Science (AAAS): 309–310. doi:10.1126/science.1065349. ISSN0036-8075. PMID11598285. S2CID130687109.
Chisholm, S.W.; Olson, R.J.; Zettler, E.R.; Goericke, R.; Waterbury, J.; Welschmeyer, N. (1988). "A novel free-living prochlorophyte abundant in the oceanic euphotic zone". Nature. 334 (6180): 340–343. Bibcode:1988Natur.334..340C. doi:10.1038/334340a0. S2CID4373102.
