Changes in the distribution and preservation of silica in the Bohai Sea due to changing terrestrial inputs

The spatial distribution of reactive silica (RSi) and organic carbon (OC) in the Bohai Sea was determined on the basis of field measurements, and budgets were calculated with support from literature data. The riverine input, primary production and water exchange between the Bohai Sea and Yellow Sea have a strong effect on the distributions of RSi and OC, with particularly high contents in sediments in the estuarine and mud areas in the Bohai Sea. Silica preservation in the sediment is more efficient than that of carbon. Exchanges via the Bohai Strait result in a net export of RSi and OC for the Bohai Sea. Increasing riverine inputs of RSi in the Bohai Sea due to water and sediment regulation since 2002 have induced a 10% increase in primary production. As a result, RSi has declined due to enhanced diatom growth and sedimentation. The Bohai Sea has thus shifted from a nitrogen to a silica limited ecosystem.