Riverine contribution of biogenic silica to the oceanic silica budget

Biological uptake of dissolved silicate (DSi) and formation of biogenic silica (BSi) during diatom growth modifies the form of Si carried from the continents to the world ocean. Significant concentrations of BSi, averaging 28.0 µmol L−1, are found in all sizes of rivers. The global contribution of BSi carried by rivers was estimated as 1.05 ± 0.20 Tmol Si year−1. Combined with the global mean riverine DSi concentration of 150 µmol liter−1, 16% of the gross riverine Si load is delivered to the world ocean as BSi. Most of this BSi would be remobilized by dissolution in marine environments. These results demonstrate that the contribution of biogenic silica carried in suspension by rivers is an important component in the world ocean Si budget that has not been recognized previously.