We measured 305 benthic fluxes of silicate (dSi) on the major sediment types across the Baltic Sea. Upscaling these data together with literature values suggested an integrated annual benthic release of dSi for the Baltic Sea being about three times larger than the diatom export production. This may explain the trend of increasing Baltic water column dSi standing stock. Reactive Si of terrestrial origin should have a much more profound influence on the Baltic Si cycle than previously known.