horizontal and vertical distribution of biogenic silica in coastal and profundal sediments of the Gulf of Finland (northeastern Baltic sea)

We studied the distribution of biogenic silica (BSi) and other potentially bio-available Si pools (NaCl-, NaBDand NaOH-extractable Si) in short (0–25 cm) sediment cores from estuarine, coastal and open-sea areas in the Gulf of Finland (northeastern Baltic Sea). The BSi pool (150–1200 μmol g–1 DM, dry matter) was the largest potentially bio-available Si pool. In a part of the studied area, the concentration of BSi increased towards the sediment surface and could be used as an indicator of eutrophication. Several profiles were uneven due to disturbances in the sediment surface layer. The concentration of BSi was higher in the eastern (> 1000 μmol g–1 DM) than in the western Gulf of Finland (ca. 500 μmol g–1 DM). Although high estuarine retention of Si occurred, its importance in the studied area was small. High local variability in BSi concentrations probably contributes to earlier found discrepancies between external load and burial of Si in the Gulf of Finland.