Reconstruction of silicon concentrations across the last interglacial-glacial transition using the silicon isotope signature of diatoms and sponges

In this project we aim to reconstruct the historical distribution of silicon concentration in Southern Ocean waters. Understanding the distribution of nutrients during the past is a fundamental prerequisite for paleoproductivity reconstructions. The distribution of nutrients (silicon, phosphate and nitrate) in the ocean is important in controlling the growth of microscopic marine algae. It is important to understand what controls the growth of these organisms because they influence the uptake of carbon dioxide (CO2) by the ocean, especially when modelling the links between the ocean and the atmosphere.

The oceanic distribution of silicon during the past is thought to have been quite different to its present-day distribution. There are, however, no proxies available to reconstruct palaeo-silicon concentrations. In this research project we are using the silicon isotope signature of diatom opal and sponge spicules to try and reconstruct the silicon concentration of the surface and deep ocean. (Collaborators: Stephen Eggins - RSES, Bill Maher - University of Canberra & Michelle Kelly - NIWA, NZ)