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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
 

Lead Supervisor: Oscar Branson, Earth Sciences

Co-Supervisor: Nicholas Tosca, Earth Sciences

Brief summary: 
Working out the mechanisms of calcium carbonate precipitation by organisms, which are critical to our ability to predict the future of Earth’s climate, and key to interpreting the record of Earth’s past.
Importance of the area of research concerned: 
Carbonate biominerals are central to the evolution of life and climate, but we do not understand how they form. The advent of carbonate biominerals allowed an explosion in biological form and function and transformed Earth’s long-term carbon cycle, leading to the climate we know today. In the ocean, benthic (bottom-dwelling) and planktic (floating) organisms such as coccolithophores, foraminifera and corals produce the majority of the biogenic calcium carbonate on Earth. The response of these marine calcifiers to anthropogenic CO2 emissions will be a major determining factor in the trajectory of climate change. The trace-element and isotope chemistry of carbonate biominerals preserved in marine sediments also provide our primary long-term archive of Earth climate history. Despite the importance of biomineralisation for biology, global biogeochemistry and climate, and as recorders of past environmental change, the mechanisms controlling their formation remain largely unknown. Understanding the mechanisms of biomineral formation is critical to our ability to predict the future of Earth’s climate, and key to interpreting the record of Earth’s past.
Project summary : 
This project will address the key question “How does the use of metastable phases in biomineral formation alter our understanding of biomineralisation and geochemistry?”, with emphasis on the role of amorphous calcium carbonate and vaterite in the formation and geochemistry of foraminiferal calcite. The first phase of the project will constrain the structure and stabilisation mechanisms of metastable phases employed by foraminifera. The second phase of the project will study synthetic analogues of these metastable phases to understand their transformation mechanisms and the influence of these transformations on the trace element and isotopic composition of the mature minerals.
What will the student do?: 
The student will conduct an extensive review of metastable phases and their stabilisation and transformation pathways. Knowledge gained during this exercise will inform novel characterisation experiments to constrain the phases involved in foraminiferal calcification. These characterisation experiments may be conducted in-house using Ramen, X-Ray diffraction or SEM/TEM imaging techniques, or at synchrotron X-ray sources. The student will then synthesise analogue phases under controlled laboratory conditions and study the structural and geochemical changes associated with phase transformations. Geochemistry will be measured using mass spectrometry facilities within the department, and resulting patterns will be interpreted within the context of foraminiferal geochemistry and biomineralisation models.
References - references should provide further reading about the project: 
Jacob et al. (2017) Planktic foraminifera form their shells via metastable carbonate phases. Nature Communications 8, 1265. https://doi.org/10.1038/s41467-017-00955-0
Zhu et al. (2021) Magnesium partitioning into vaterite and its potential role as a precursor phase in foraminiferal Mg/Ca thermometer. Earth Plan. Sci. Lett. 567, 116989. https://doi.org/10.1016/j.epsl.2021.116989
Evans et al. (2020) Trace and major element incorporation into amorphous calcium carbonate (ACC) precipitated from seawater. Geochim. Cosmochim. Act. 290, 293-311. https://doi.org/10.1016/j.gca.2020.08.034
Applying
You can find out about applying for this project on the Department of Earth Sciences page.
Prof Nicholas Tosca
Dr Oscar Branson
Department of Earth Sciences Graduate Administrator