Dissolution kinetics of biogenic silica and tentative silicon balance in the Yellow Sea

Abstract

AbstractThe dissolution of biogenic silica (bSiO2) in coastal environments is important for marine productivity and essential to the global silicon cycle. BSiO2 dissolution experiments were performed using sediments from the Yellow Sea (YS) to explore the factors that influence bSiO2 dissolution and to better understand the silicon cycle in the YS. The results showed that the bSiO2 content in surface sediments varied from 0.40% to 3.7% (average 2.2% ± 0.79%, SiO2%). Additionally, the bSiO2 content was higher in the central areas of the northern and southern YS and lower in the near‐shore area of the northern Changjiang Estuary. The burial flux of bSiO2 in surface sediments ranged from 0.12 mol m−2 yr−1 to 2.3 mol m−2 yr−1 and gradually decreased eastward from near shore to offshore. Continuous flow experiments showed that the solubilities of bSiO2 in the YS sediments varied from 91.0 to 303 μM‐Si. Further, the dissolution rate constant of bSiO2 was 9.3–41 nmol g−1 h−1, which is 2–3 orders of magnitude lower than that of other marginal seas such as the Arabian Sea and Scotia Sea. The structural incorporation of aluminum in bSiO2 and the content of lithogenic minerals in sediments hindered bSiO2 dissolution. The silica budget of the YS was established. The burial efficiency of bSiO2 in the surface sediment was calculated to be 73%, which accounts for 4% of the global balance and is much higher than that of the global ocean average. Because of its high sediment accumulation rate and much lower dissolution rate constant, bSiO2 was well preserved in the YS, highlighting the important role of the YS in the global silicon cycle.