סמינר בכימיה פיזיקלית: Biochemical remodeling of phytoplankton cell composition under climate change

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Abstract:

Half of global primary productivity occurs in the ocean by unicellular, photosynthetic microorganisms called phytoplankton. Their activity sustains the entire marine food web and influences Earth’s biogeochemistry and climate. Unlike organisms that maintain strict chemical homeostasis, phytoplankton elemental composition (mainly the carbon-to-nitrogen-to-phosphorus ratio) varies under different environmental conditions. In my research, I explore the causes and biogeochemical consequences of such variations. I approach these topics through a combination of theory, experiments, and models of hierarchical complexity, informed and constrained by laboratory and field observations.

In my talk, I will focus on my postdoctoral work, during which I developed the “Darwin” model, the ecological and biogeochemical module of the MIT general circulation model, to include variations in phytoplankton macromolecular composition (i.e., proteins, lipids, and carbohydrates). Using this model, I simulate the global distribution of phytoplankton macromolecular and elemental composition at present, and under a warmer climate. My major finding is that under warming, phytoplankton will alter their composition, becoming more “junk food” (i.e., higher in calories but lower in nutritional value) due to changes in environmental conditions. In situ macromolecular measurements in polar regions show trends consistent with our predictions. Our findings indicate that changes in the macromolecular composition of phytoplankton can serve as indicators of shifting environmental conditions. Such changes will reshape the nutritional landscape at the base of the marine food web and alter global biogeochemical cycles.

מארגן הסמינר: פרופ' איליה קמינקר