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Xiaole Sun: Silicon isotope-based reconstruction of the silicon cycle and diatom production in the Baltic Sea; Implications for climate change and eutrophication
The objective of the 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 waters, Baltic Sea water, phytoplankton material and marine 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 (DSi) concentrations caused by damming of rivers and eutrophication and the response of diatoms 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 to promote the understanding of longer-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 that 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.The project will address the following items: i) Characterisation of Si inputs and its isotope values, ii) Si isotope composition of BSi in Baltic Sea sediments, iii) Modelling of Si isotopes in the Baltic Sea and iv) Budgets of diatom production and carbon sequestration based on isotope values of Si during the last 1000 years.
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