Project period: 2023
Contact: Dr. Zofia Dubicka
Calcium carbonate minerals produced by marine organisms play a central role in the global carbon cycle and carbonate sedimentation, which influence the climate by regulating atmospheric CO2 levels. Foraminifera are important marine single-celled organisms that produce calcite shells for over 300 million years. Foraminiferal biominerals are commonly utilised as reliable proxies for past environmental conditions such as climate changes, sealevel fluctuations or oceanic acidifications as their skeletons are archives of geochemical parameters (stable isotope and trace elements) of the ancient sea water. Understanding of the way how these organisms produce their skeleton is a precondition to correctly interpret geochemical data. Unfortunately, up to now many of the fundamental problems of foraminiferal biomineralization have not been resolved.
The aim of the project is to study the biomineralization mechanisms of foraminifera using complementary techniques. I plan to integrate fluorescence imaging of living cells by confocal/multi-photon laser scanning microscopy (CLSM) with application of various fluorescence markers with examination of fixed foraminifera at different stages of calcification by e.g., field-emission scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometry (EDS), electron backscatter diffraction (EBSD), field-emission electron probe microanalyzer (EPM-WDS) and transmission electron microscopy (TEM).
Project period: 2022 - 2023
Contact: Dr. Anke Neumann Jenal
Clay minerals are ubiquitous in sediments and soils and have long been regarded as mostly unreactive but are emerging as potentially important redox-active minerals in natural environments. Intriguingly, their interaction with the naturally abundant reductant ferrous iron leads to the formation of transient, yet highly reactive mineral species capable of degrading recalcitrant contaminants. We suspect that the mineral identity and crystallinity of these mineral species is key to the reactivity observed and hence to understanding their role in many of Earth’s crucial element cycles, as well as nutrient availability, and contaminant degradation.
The target minerals are likely amorphous or nano-crystalline, present in low abundance and most often made up of particles of very small sizes (nanometer range). Thus, facilities and analytical tools that cannot just identify but fully characterize these nanophases are needed. At GFZ, high-resolution transmission electron microscopy (HR-TEM) and atomic pair distribution function (PDF) method will be used and complemented with Mössbauer spectroscopy at Newcastle University. Insights from this project will improve our understanding of how clay mineral redox reactions control the identity and reactivity of reactive mineral intermediates and, hence, how clay minerals control redox reactions on Earth.
Project period: 2021 - 2023
Contact: Dr. Elizaveta Kovaleva
The research project aims at understanding the impact cratering process, its conditions and effects, by constraining the pressure-temperature (P-T) phase diagrams (geo-thermobarometry) and geochronological studies (age dating) for accessory minerals that experienced shock deformation. The project will be realized via search and identification of the new shock microstructures in accessory minerals; study of known shock microstructures in accessory minerals (microtwins, planar fractures, neoblastic granular textures, inclusions of high-pressure polymorphs), and determining their formation mechanisms and the age of shock deformation. Besides, I will study the spatial distribution of shocked minerals within the target rocks relative to the crater center and the shock-induced melt bodies within the impact structure; conduct the estimation and calibration of the shock pressures throughout the crater with in situ studies of shocked minerals; correlate shock microstructures found in different minerals and various types of impactites from different impact craters.
Publikationen
Kovaleva, E., Helmy, H., Belkacim, S., Schreiber, A., Wilke, F. & Wirth, R. (2023): Libyan Desert Glass: New evidence for an extremely high-pressure-temperature impact event from nanostructural study. - American Mineralogist, 108(10), 1906-1923. https://doi.org/10.2138/am-2022-8759
Kusiak, M., Kovaleva, E., Vanderliek, D., Becker, H., Wilke, F., Schreiber, A., Wirth, R. (2022): Nano- and micro-structures in lunar zircon from Apollo 15 and 16 impactites: implications for age interpretations. - Contributions to Mineralogy and Petrology, 177, 112.
https://doi.org/10.1007/s00410-022-01977-8
Kovaleva, E., Kusiak, M. A., Kenny, G. G., Whitehouse, M. J., Habler, G., Schreiber, A., Wirth, R. (2021): Nano-scale investigation of granular neoblastic zircon, Vredefort impact structure, South Africa: Evidence for complete shock melting. - Earth and Planetary Science Letters, 565, 116948.
https://doi.org/10.1016/j.epsl.2021.116948
Project period: 2021 - 2023
Contact: Dr. Runa Antony
Light absorbing organic matter, together with mineral dust and pigmented microbes, massively reduce the snow and ice surface albedo (amount of solar energy reflected from the ice surface). This leads to increased solar radiation absorption, resulting in accelerated melting of the ice sheet surface.
I aim to derive a quantitative and qualitative understanding of the nature, sources, on-ice microbial processing and fluxes of organic matter on the ever-changing ice surface during melting. This way I hope to provide novel, holistic insights on the interplay between microbial metabolism, carbon cycling and surface melting and help fine tune the response of Greenland’s ice masses to future climate warming scenarios in global predictive models.
Project period: 2019 - 2021
Contact: Dr. James Bradley
The Greenland lce Sheet Surface (GrISS) hosts diverse communities of microorganisms and algae whose activity controls transfers and transformations of carbon and nutrients, and albedo (and thus melting). A numerical tool to capture the biological and biogeochemical processes on ice surfaces currently does not exist, and thus a fully mechanistic understanding of these processes is lacking. Without this tool, quantifying and predicting past, present and future GrISS biogeochemical processes and their associated global feedbacks is impossible. I will address this key knowledge gap by developing and implementing a new modelling tool used to simulate biogeochemical processes on the GrISS and the susceptibility of these processes to climate change. The model will also guide future experimental efforts and act as a cross-disciplinary knowledge-sharing platform. This fellowship will provide me with the means to become an expert in developing, applying and integrating numerical and experimental techniques and benefit my future career.
Project period: 2022 - 2023
Contact: Dr. Lukasz Stachnik
Climate change inducted glacier ablation is strongest in polar regions and enhances water runoff and sediment mass flux to the aquatic system. Meltwater transports bioavailable and bio-limiting nutrients that lead to an increase in primary production facilitating CO2 consumption in the marine environments (process called “biological pump”). Biogeochemical studies focused mainly on dissolved macronutrients (mainly Fe, Mn) and little emphasize has been put on micronutrients adsorbed on suspended particulate matter (e.g., Fe, Mn, Zn, Co, Cd, Mo, Ni), which are important for limiting biological marine production. For glacierised basins outside of Ice Sheets, there is a limited data on secondary phases consisting of micronutrients adsorbed onto the suspended particulate matter. Furthermore, recent studies have mainly focused on aquatic ecosystems affected by meltwater from the Greenland Ice Sheet (underlain by ingenuous bedrock) and analyses were mainly performed on iron.
The aim of the fellowship is to determine the impact of glacier-derived nutrients on negative feedback effect leading to a potential CO2 consumption. The study will be focused on High Arctic glacierised basin underlain by sedimentary/metasedimentary rocks, which are underrepresented in the recent studies.