Hidden comet tails of marine snow impede ocean-based carbon sequestration [research article summary]
Chajwa, Rahul ; Flaum, Eliott ; Bidle, Kay D. ; Van Mooy, Benjamin ; Prakash, Manu
Gravity-driven sinking of "marine snow" sequesters carbon in the ocean, constituting a key biological pump that regulates Earth's climate. A mechanistic understanding of this phenomenon is obscured by the biological richness of these aggregates and a lack of direct observation of their sedimentation physics. Utilizing a scale-free vertical tracking microscopy in a field setting, we present microhydrodynamic measurements of freshly collected marine snow aggregates from sediment traps. Our observations reveal hitherto-unknown comet-like morphology arising from fluid-structure interactions of transparent exopolymer halos around sinking aggregates. These invisible comet tails slow down individual particles, greatly increasing their residence time. Based on these findings, we constructed a reduced-order model for the Stokesian sedimentation of these mucus-embedded two-phase particles, paving the way toward a predictive understanding of marine snow.</p>
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