Claudia Ehlert

1. Introduction Silicon (Si) is a major constituent of Earth's silicate crust that is released to solution during rock weathering and delivered to the ocean by rivers, where it sustains the productivity of marine biosilicifying organisms (Tréguer and De La Rocha, 2013). Oceanic Si concentrations also determine the rate of authigenic clay formation in sediments, which has been proposed to influence global climate through its effects on the marine carbonate balance (Mackenzie and Garrels, 1966).