Si isotope-based reconstruction of silicon cycle and diatom production in the Baltic Sea; implications for eutrophication and climate change

The objective of my PhD study is to reconstruct diatom productivity and carbon sequestration in the Baltic Sea over the last 1000 years by means of d30Si isotope signatures in river water, Baltic Sea water, phytoplankton and sediments. These isotope signatures will be compared with a recently developed Si budget for the Baltic Sea. The Baltic Sea is one of the many aquatic ecosystems around the world that show long-term decreases in water column dissolved silicate concentrations, caused by damming of rivers and eutrophication; the response of diatoms to these changes will be reflected in the d30Si isotopic signature in the sediment. Moreover, available data on allochthonous and autochthonous Si fluxes in the Baltic Sea together with the new information on their d30Si isotope signatures will allow promoting the understanding of long-term variations in d30Si in the sedimentary record of the global ocean. The Baltic Sea is a unique model system due to its semi-enclosed character which makes it possible to investigate and use isotope data to constrain marine Si budgets and the significance of the biological pump for long-term C sequestration.

Contact information:
Xiaole Sun
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