Hidden comet-tails of marine snow impede ocean-based carbon sequestration

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 phenomena is obscured by the biological richness of these aggregates and lack of direct observation of their sedimentation physics. Utilizing a scale-free vertical tracking microscopy in field setting, here we present micro-hydrodynamic 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 halo around sinking aggregates. These invisible comet-tails slows down individual particles, dramatically increasing their residence time. Based on these findings, we construct a reduced order model for the Stokesian sedimentation of these mucus-embedded two-phase particles, paving the way towards a predictive understanding of marine snow.