Dissolved silica

Oceanic silicic acid

Dissolved silica (DSi) is a term used in the field of oceanography to describe the form of water-soluble silica, which is assumed to be Si(OH)₄ (orthosilicic acid) or its conjugate bases (orthosilicate anions) such as O−Si(OH)₃ and (O−)₂Si(OH)₂. Theoretical computations indicate that the dissolution of silica in water proceeds through the formation of a SiO₂·2H₂O complex and then orthosilicic acid. The biogeochemical cycle of silica is regulated by the algae known as the diatoms. These algae polymerise the silicic acid to so-called biogenic silica, used to construct their cell walls (called frustules).