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Rahul Chajwa (Stanford University, USA)
Date & Time
Wed, 01 May 2024, 14:30 to 16:00
Chern Lecture Hall

The gravity-driven downward flux of carbon in our oceans in the form of marine snow, commonly referred to as a biological pump, directly regulates our climate, and the vertical migration of plankton adds further richness to this phenomenon. In this talk, I will share [1] an inflation-induced motility mechanism in plankton that allows single cells to vertically migrate distances ∼105 times their own size in the absence of swimming and advective transport. We find that a dynamic buoyancy during the cell cycle via rapid inflation contributes a singular perturbation to migration dynamics. We show that treating gravity as selection pressure in the evolution of phytoplankton leads to critical bounds on cytoplasm and vacuole densities in non-motile plankton. [2] Sedimentation of marine snow presents a notoriously difficult fluid-structure interaction problem. We conduct a highly resolved PIV of marine snow at sea, which presents detailed fluid-structure dynamics, revealing an invisible comet-tail like morphology composed of mucus. We construct a minimal model of Stokesian sedimentation and viscoelastic distortions of mucus to understand the sinking speeds and tail lengths of marine snow and find that these hitherto unknown invisible degrees of freedom significantly impede carbon sequestration.


[1] A. Larson*, R. Chajwa*, H. Li, M. Prakash, Inflation induced motility for long-distance vertical migration, bioRxiv 2022.08.19.504465 (2022)

[2] R. Chajwa, E. Flaum, K.D. Bidle, B.V. Mooy, M. Prakash, Hidden Comet-Tails of Marine Snow Impede Ocean-based Carbon Sequestration, arXiv:2310.01982 [] (2023)


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Meeting ID: 910 9968 7605
Passcode: 010203