NOir – Nutrient budgets in the Ocean in recent and past environments: Foraminifera as keyplayers and archives

• Applicant: Dr. Nicolaas Glock
• Subject Area: Palaeontology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 447553644

This part of the NOir project will focus on a climate relevant biogeochemical cycle: the marine nitrogen cycle. Nitrogen (N) is a fundamental component of amino and nucleic acids and thus essential for all living organisms. Nitrate (NO3-) is an important limiting macronutrient and the most abundant form of oceanic reactive N. The NOir project will utilize fossil foraminifera to reconstruct past NO3- concentrations ([NO3-]) in the intermediate Pacific over the last deglaciation. In order to predict future changes in marine nutrient budgets, it is not only important to develop a comprehensive understanding about the recent nutrient cycles but also to reconstruct past nutrient cycling focusing on periods with rapidly changing climatic conditions. The terminations of global ice-ages are one of the best examples for the Earth’s dramatic environmental variability. While the global cooling and the time for the ice sheets to reach their maximum extent was relatively slow, the posterior warming and ice-sheet retreat was more abrupt. Within the NOir project we will use and refine a new, state-of-the-art multiproxy approach, using benthic foraminifera as archives to quantitatively reconstruct deglacial [NO3-] and redox conditions. The proxy set will be applied over the last deglaciation at four oxygen-depleted locations in the East Pacific, the Sea of Okhotsk and the Gulf of California to achieve a widespread reconstruction in different parts of the main Pacific basin and to get a comparison to records from marginal sea basins still bathed in water masses from the Pacific. The reconstruction of oxygenation and nutrient budgets in oxygen depleted regions is of special interest, considering the growing concern about ongoing ocean deoxygenation decline due to anthropogenic climate change.Foraminifera are amoeboid protists, typically covered by a test, and populate a diverse range of marine habitats. The tests of calcitic species are well preserved as fossils in the sedimentary record and perfect archives for various paleoproxies. NOir will use morphological characteristics, i.e. the porosity of the benthic foraminifer Bolivina spissa, and geochemical signatures, i.e. the Mn/Ca ratio, the stable carbon (C)-isotope composition of benthic foraminiferal calcite (δ13CFORAM) and the stable nitrogen (N)-isotope fractionation of organic matter (δ15Norg), as [NO3-]- and redox-proxies. There are strong feedbacks between oceanic N-inventories and climate, due to the coupling of the biogeochemical C- and N-cycles through the biological C-pump. The C-cycle is a main driver of climate change. With the reconstruction of past N-cycling, the NOir project will thus contribute to a more comprehensive understanding of climatic variability, a key objective in contemporary earth sciences. This research grant (“Sachbeihilfe”) proposal is a complementary proposal to the proposal for the Heisenberg Fellowship by Nicolaas Glock that has been submitted in parallel.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Professor Dr. Frans Jorissen