Delayed settling of marine snow at sharp density transitions driven by fluid entrainment and diffusion-limited retention

摘要: Marine snow is central to the marine carbon cycle, and quantifying its small-scale settling dynamics in different physical environments essential understanding role bio- geochemical cycles. Previous field observations of aggregate thin layers associated with sharp density gradients have led hypothesis that these may be caused by a decrease speed at interfaces. Here, we present experimental data on aggre- gate behavior, showing particles can dramatically their veloc- ity when passing through transitions. This delayed 2 potential mechanisms: (1) entrainment lighter fluid from above as particle passes gradient, (2) retention transition driven changes par- ticle due porosity. The aggregates observed this study exhibited distinct behav- iors transition. Quantitatively comparing predictions models allow us infer first group was primarily diffusion-limited retention, whereas dominant mechanism for second group. Coupled theory, our results demonstrate both play an important determining thus pro- vides insight into ways lead formation layers, biological hotspots affect trophic dynamics, biogeochemical cycling ocean.