Diatoms are key primary producers and therefore make an important contribution to carbon export. These phytoplankton utilise dissolved silica (DSi), sourced from riverine, atmospheric, sedimentary and hydrothermal inputs, and convert it to biogenic silica (bSiO₂). Some of this bSiO₂ dissolves in the water column, regenerating the DSi pool, whereas the remaining fraction settles out to the sediments (e.g. via aggregates) to form bSiO₂ accumulations. These occur primarily in the Southern Ocean and provide a sedimentary archive regarding export production over hundreds to millions of years.