Dissolved silica in pore waters of Lakes Ontario, Erie, and Superior sediments

The distribution of dissolved silica in pore waters from Lakes Ontario, Erie, and Superior sediments is not directly related to the deposition of diatomites from the overlying water. It is proposed that silica concentrations in the pore waters are controlled by dissolution of ferroaluminum silicate, Al1−xFe1−x3+(SiO2)x(OH)6(1−x). The cryptocrystalline complex is formed in the sediments by the reaction of biogenic silica with aluminum and ferric oxyhydroxides or by the hydrolysis of clay minerals. A massive episodic flux of biogenic silica to the sediments follows the crash of diatom blooms. Most of the biogenic silica is however dissolved in the water column or at the sediment‐water interface; a small fraction is fixed permanently in the sediments as the cryptocrystalline complex. Budget calculations show that regeneration of silica from Ontario and Erie sediments far exceeds annual input from external sources.