Abstract:Silicon is crucial in numerous biochemical and geochemical processes, its cycle is a hot issue of global environmental change and also an important area of marine science. Despite the importance of silicon, less knowledge is available on wetland silicon cycle. Base on the investigation in Yellow River estuary wetland in January of 2011 and October of 2012, distributions and sources of biogenic silica (BSi) were discussed. The results showed that: BSi in soil ranged from 2.48 to 19.3 g/kg, a significant linear relationship was found between BSi and particle organic carbon (POC) and particle organic nitrogen (PON), which indicated their sources were same to some extent. Phytoliths were very rich in surface sediment, with forms of spiny bar, bar, pie, short saddle, corrugated shape, triangle, dumb-bell shape, etc. Spiny bar and dumb-bell shape were main forms of phytolith in I area of the Yellow River estuary wetland. While smooth bar model was the dominant form in II area. In this study, BSi in sediment was composed by diatoms and phytolith. As a small amount in the BSi, part of phytolith in I area came from the basin of Huanghe River transferred by river. While in II area, most of phytolith came from sediment of the Huanghe River deposited before the Yellow River diversion. Phytolith is co-affacted by river and ocean and may influence the silicon cycle in Huanghe River and Bohai Sea.