Dissolution of biogenic silica: Roles of pH, salinity, pressure, electrical charging and reverse weathering. Geologica Ultraiectina (302)

The recycling of biogenic silica (bSiO2) produced by diatoms is a vital process sustaining a significant fraction of primary production in the oceans. The efficiency with which bSiO2 dissolves controls the availability of nutrient silicon in the water column, and modulates the export of organic carbon to the deep sea. Environmental conditions during biomineralization affect the silicification and weathering resistance of diatom frustules, while ecosystem processes are determining factors for the recycling of bSiO2 in the water column. The dissolution rate of diatom frustules is a function of the physicochemical properties of both the silica and the aqueous medium. This thesis focuses on the biogeochemical processes, physicochemical variables (salinity, pH, and pressure) and material properties that affect the recycling efficiency of biogenic silica, in the water column, in marine sediments and along the land to ocean continuum. It provides an overview of the current knowledge on the subject, and presents novel findings based on laboratory and field experiments.