Sallie Penny Chisholm - Chisholm sees big impacts from small sources
An ocean of opportunity
Jennifer Chu | MIT News Office
April 14, 2015
a beaker into any portion of the world’s oceans, and you’re likely to
pull up a swirling mix of planktonic inhabitants. The oceans are teeming
with more than 5,000 species of phytoplankton — microscopic plants in a
kaleidoscope of shapes and sizes. Together, phytoplankton anchor the
ocean’s food chain, supplying nutrients to everything from single-celled
organisms on up to fish and whales.
Through photosynthesis, these tiny organisms supply more than half
the world’s oxygen. When these plants die, they drift to the ocean
bottom, or evaporate into the air as carbon — a process that generates
more than half the world’s cycling carbon.
Phytoplankton play a fundamental role in regulating Earth’s climate.
But figuring out exactly how these organisms contribute to climate
change is a tricky undertaking, primarily because they are so diverse:
Any given species may have a set of genetic or physical characteristics
entirely different from any other, leading to different behaviors and
Such diversity can appear, at the outset, “bewilderingly complex,”
says Mick Follows, an associate professor of oceanography in MIT’s
Department of Earth, Atmospheric and Planetary Sciences (EAPS). He says
wrestling such diversity into global climate models is a futile task.
But lumping phytoplankton into a big “black box” can be equally
Instead, Follows is working at an intermediary level, developing
models of marine microbes at the cellular and community levels, to tease
out fundamental processes that may be worked into global climate
“We’re starting to open up the black box of simple models,” Follows
says. “There’s a balance: Do you want to understand every detail of the
world, or do you want to be able to stand back and have a big picture
view? Somehow you have to keep circling around it from both directions
to develop that view.”
For more than 20 years, Follows has worked as a research scientist at
MIT, answering such questions. He was granted tenure as an associate
professor in 2013.
“I’m now interacting with undergraduates in a way I wasn’t doing in
my little research hole, and I have a whole new appreciation for the
broader aspects of MIT,” Follows says. “I feel much more connected to
the Institute as a whole.”
An ocean of opportunity
While growing up, Follows didn’t expect he would end up in academia: School wasn’t a priority then.
Follows grew up in a small town in the British region of East Anglia,
and fondly remembers “riding bikes around the countryside, and living
His father was a typesetter at a local newspaper, and his mother
worked in a men’s clothing shop. Both his parents have roots in
Manchester — “a downtrodden, post-industrial place,” Follows says —
where his mother was nevertheless able to win a scholarship to a good
“She worked in shops, and in the field, but would be quoting Shakespeare,” Follows says of his mother’s path.
Follows was less inclined toward school, and ended up leaving high
school. “I don’t think people think of me this way now, but I was a bit
of a loudmouth,” Follows recalls.
He ultimately continued his studies at a community college, and spent
a year at an art school — a fact that he’d rather overlook: “My work
was rubbish — terrible!”
He then decided to pursue studies in math and physics at the
University of Leeds. “I liked the organization [the subjects] brought to
the world,” Follows says. While exploring graduate programs, he was
particularly drawn to atmospheric science. Follows enrolled at the
University of East Anglia, where he earned a master’s degree and a PhD
in atmospheric sciences, studying atmospheric circulation of ozone. In
his research, he began to see parallels between the atmosphere and the
“How ozone gets down from the stratosphere to troposphere, there’s an
analogous process, flipped, when you think of how nutrients get from
the subsurface to the surface of the ocean, and I started thinking more
about the ocean,” Follows says.
In particular, Follows felt there was an opportunity to contribute to
a then-emerging field. “While coupled circulation and chemistry models
were established for the atmosphere, the same was just spinning up in
the oceans,” Follows says. “It seemed the ocean world was a bit less
crowded, and there were interesting problems.”
Follows credits his colleague John Marshall, now the Cecil and Ida
Green Professor of Oceanography, for providing his path to MIT. Follows
was still at the University of East Anglia when he first met Marshall,
then a postdoc at Imperial College London.
“Being as I was the local guy, I said, ‘I’ll show you a place where
we can go get a meal,’” Follows recalls. “I sat next to John and said,
‘Are you looking forward to going to MIT?’ And he kind of frowned as he
does, and said, ‘You want to go?’”
A few weeks later, Marshall called Follows about a postdoc position
opening up at Imperial College. Follows accepted the position, and then
after a year, received a similar call from Marshall, this time to MIT.
In 1992, Follows arrived on campus as a postdoc, and stayed for the next
20 years as a research scientist.
From a black box to the real world
At MIT, Follows has devoted his research to understanding the
biological processes of phytoplankton and other microbes that contribute
to the Earth’s carbon cycle. Initially, though, every microbe seemed to
He eventually teamed up with Sallie “Penny” Chisholm, the Lee and
Geraldine Martin Professor in Environmental Studies at MIT, who
discovered Prochlorococcus —the most abundant photosynthetic organism in
the world. Chisholm was studying subpopulations of Prochlorococcus, and
mapping individual communities in the ocean.
“Suddenly there was a beautiful system where organisms that are
almost the same, but not quite, are taking different habitats, occupying
different niches in the environment,” Follows says.
Chisholm’s data of diverse microbes stirred up an idea: What if the
diversity in phytoplankton could be modeled based on natural selection?
Could one predict the makeup of a microbial community, based on its
inhabitants’ traits? It was a simple idea, and yet no one had attempted
to realize it in global models.
Follows and his group developed a model — essentially a virtual ocean
environment — in which a realistic set of microorganisms with diverse
traits can interact and compete. The model determines which traits are
the fittest phenotypes — the ones that will dominate in a given ocean
“I think that in the field, we had reached a bit of a stalemate,
where you would just keep adding more parameters and tuning more knobs
to fit the real world,” Follows says. “We turned around and said, ‘Let’s
build a videogame — make an environment, throw some players in, ask how
the system organizes itself, and acknowledge that in the real world,
there is a huge diversity of organisms.’”
This radical thinking earned Follows a grant from the Moore Foundation in 2007, which he used to start the Darwin Project,
a cross-campus collaboration between oceanographers, biogeochemists,
and marine microbiologists at MIT to develop global ocean-circulation
models built around fundamental microbial processes.
Follows is continuing to run the Darwin Project, and just recently
became a member of SCOPE — the Simons Collaboration on Ocean Processes
and Ecology — a five-year project based at the University of Hawaii. He
and his fellow researchers will measure and model ocean communities
around Hawaii, which are thought to be representative of a large swath
of the North Pacific. Their goal is similar to Follows’ original vision:
to elucidate how such tiny organisms can have such huge climatic
“The climate system is incredibly tied up with life,” Follows says.
“You can think of man in the same way as those first photosynthetic
bacteria that changed the planet in a radical way, to a completely
different set of requirements if you wanted to survive on that planet.
Are we that thing now? Or are we a blip? It’s interesting to put it in