Congratulations to Stephanie Dutkiewicz, recently promoted to principal research scientist in MIT’s Center for Global Change Science, and still associated with the Earth, Atmospheric, and Planetary Science department. Stephanie focuses on biogeochemical cycling and phytoplankton distribution in the ocean. Her research follows the circulation of the ocean, from the surface waters to the depths, and back. Within that cycle, Stephanie focuses on another cycle: she models how oceanic circulation affects the flux of carbon and other nutrients, how the consequent availability of these nutrients drives phytoplankton distributions, and how changes in the phytoplankton community in turn drive changes in nutrient distribution.
Stephanie’s work begins with 3-Dimensional modeling of how ocean waters move and mix, an effort accomplished through collaboration with MIT research scientist Jeffrey Scott. She then overlays information on how carbon, nitrogen, phosphorus, and other nutrients move on top of these computer simulations.
Next, Stephanie models the biological component. “The oceans are responsible for about 50% of primary production,” explains Stephanie. “So 50% of the sunlight that is taken into the body of plant-like organisms (phytoplankton) occurs in the ocean.” These organisms take up carbon and other nutrients and, upon dying, some fraction sink to the bottom of the ocean, carrying those nutrients with them.
But not all phytoplankton are created equal — some species are better able to act as carbon sinks than others. Phytoplankton structure and type is driven by ocean circulation and the distribution of nutrients. Large species pull more carbon into deep ocean reservoirs when they sink; smaller species less.
As climate change affects ocean circulation and nutrient availability, some species may become “winners”, filling ecological niches and spreading to new geographical regions. Other species may die out. Stephanie models how these community structures change in the future, and how those changes in turn affect carbon cycling.
Unfortunately, it seems climate change favors mostly the smaller species, resulting in less of a carbon sink. “Understanding climate change means understanding feedbacks,” says Stephanie. “If the ocean takes up less carbon, that’s a feedback into the carbon system.”
During her 12 years at MIT, Stephanie has contributed to the development of the MIT Joint Program’s Integrated Global Systems Model (IGSM) and collaborated with the MIT Climate Modeling Initiative and the Darwin Project. “I really like the group of people I’m working with. Developing this model has been quite exciting — it’s a good place to be.”
Schematic of a sample marine ecosystem model - source: Dutkiewicz (2012)
The work by Stephanie and her group is featured in the July 2012 issue of Microbe magazine. An animated MOVIE of the simulation shown below is available here.
The distribution of virtual autotrophic marine microbes. The simulation shown uses an ecosystem model initialized with 78 virtual phytoplankton types which were all assigned to one 4 functional groups indicated here in color. Green and blue colors indicate biomass dominated by cyanobacteria and pico-eukaryotes; red indicates diatoms and yellow other eukaryotes. Brighter regions have higher biomass. The diatoms and larger eukaryotes dominate in highly seaonal regions with high nutrient supply, while the cyanobacteria and pico-eukaryotes dominate in the more stable tropics and subtropics. The physical virtual environment was a high resolution (18km) version of the MIT general circulation model developed by the Estimating the Circulation and Climate of the Oceans Consortium (ECCO). The simulation was performed by Oliver Jahn, MIT, with help from Michael Follows, Stephanie Dutkiewicz and Christopher Hill, MIT. Figure provided by Oliver Jahn.
