Importance of particle formation to reconstructed water column biogenic silica fluxes

Abstract : The particles sinking out of the ocean's surface layer are made up of a mixture of living and dead algal cells, fecal pellets, and aggregates, while the parameters used to describe the behavior of biogenic silica (bSiO2) in today's models are experimentally determined on freely suspended diatoms (FC). In a simple advection-reaction model we combine sinking rates of FC, zooplankton fecal pellets, and aggregates with recent measurements of bSiO2 dissolution to reconstruct theoretical downward profiles of bSiO2 fluxes at eight sites in the world ocean. Statistical analyses showed that sinking and dissolution parameters for two pools of bSiO2 are required to model particle fluxes accurately. The two-pool model results confirm the importance of seasonality for particle formation and its connection to the percentage of the bSiO2 production that reaches the seafloor. The depth of bSiO2 recycling appears to be influenced more by particle formation than by dissolution rates of bSiO2 or the ballast effect of the dense diatom frustules.