Diatoms contribute over 75 % of annual primary production in the Southern Ocean, resulting in a strong coupling of silica and carbon cycles in the region. However, a mechanistic understanding of the full extent of these interactions in the modern-day ocean is still not fully developed. Si fractionation by diatoms in the formation of siliceous frustules is the primary process controlling seawater δ³⁰Si variations and can therefore be used as a tool to shed light on the interactions of diatoms with carbon export processes in the marine environment.

This work aims to uncover linkages between carbon and silica cycling across different temporal and geographical scales in the Southern Ocean. This includes examination of δ³⁰Si of sinking particulate material on the Western Antarctic Peninsula shelf, through the water column over a long transect across the Scotia and Weddell Seas, ands around the perimeter of a giant iceberg in the south Scotia Sea. The use of other stable isotope analyses will provide information on phytoplankton community composition (using δ¹³C), trophic transfer and community structure (using δ¹⁵N), and water mass composition and nutrient supply (using δ¹⁸O).

This work will contribute to developing a mechanistic understanding of silica and carbon cycle linkages, allowing consideration of the impact of changes to the Southern Ocean silica cycle on the future state of the ocean carbon sink and climate.