Those sinking moments: measuring sedimentation dynamics of marine snow

Ecosystems on our planet are driven out of equilibrium with energy input from the sun resulting in a flux of matter across food chains, contributing to the global carbon cycle. This flux is remarkably vivid in the biological pump of our oceans, with gravity driving the downward flux of carbon in the form of marine snow. Using a newly invented hydrodynamic levitation based microscopy [Nature Methods vol. 17, 1040–1051 (2020)], we measure the sedimentation dynamics of marine snow aggregates in the Gulf of Maine; highlighting the dynamic nature of marine snow aggregates. Drawing on the insights from field observations, we construct a minimal model based on far-field Stokesian hydrodynamics with inter-particle stickiness, and numerically explore the formation of these aggregates from an initially homogeneous sedimenting suspension. Our experimental observations and theoretical model paves the way for understanding the structure and dynamics of marine snow; thus offering a new window into the physics of Carbon transport in the ocean.