Effects of biogenic silica dissolution on silicon cycling and export production

Abstract

Biogenic silica (bSiO2) dissolution plays an important role in the marine silicon cycle, diatom production and vertical export production. An ocean ecosystem model that incorporates dependency of bSiO2 dissolution on water temperature was used to examine the effects of bSiO2 dissolution on diatom production and bSiO2 export. Diatoms dominate with higher bSiO2 dissolution rates because of enhanced silicic acid supply for diatom production. Annual bSiO2 export does not change with bSiO2 dissolution rate, because of less bSiO2 production with lower rates and greater bSiO2 dissolution with higher rates. The ratio of bSiO2 export to production changes seasonally, with maximum in late spring. The contribution of spring diatom bloom to the annual bSiO2 export is 21-30%, smaller than observation-based estimates. This suggests necessity for incorporating other factors controlling bSiO2 dissolution besides water temperature, such as difference in organic coating protections against bSiO2 dissolution between live and dead diatoms, in the model. Copyright 2005 by the American Geophysical Union.