Opal studied as a marker of paleoproductivity

Abstract

Biogenic silica, better known as opal, is one of the three biogenic components of pelagic sediments, along with carbonate and organic matter, and it is a powerful tool for understanding the carbon cycle of the present and past. Opal is formed in surface waters during the photosynthesis of siliceous phytoplankton such as diatoms. After cells die, they sink through the water column; the fraction that is not dissolved ultimately is buried in the underlying sediments. In the modern ocean, siliceous phytoplankton generates more than 50% of the biological pump of CO 2 .