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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - ZOOMecular (Read the fine print: Zooming into paleoenvironmental and biogeochemical processes through molecular imaging of biomarker distributions in sediments)

Teaser

Summary

The project ZOOMECULAR (https://www.marum.de/en/about-us/HinrichsLab-ZOOMecular.html) seeks to exploit laser-based molecular imaging technologies, which have been largely developed for applications in medical and life sciences, for novel applications in the geosciences. Our main targets are lipid biomarker molecules, which bear diagnostic information on their biological sources and the environmental conditions in which they are produced. Such biomarkers are ubiquitous components of sediments and rocks, and are widely used for the reconstruction of paleoenvironmental conditions and for the study of microbial communities that inhabit sedimentary environments, where they mediate important biogeochemical processes. However, analysis by conventional approaches requires gram- and centimeter-sized samples. Within the ZOOMECULAR project, we interrogate dated sediment samples by molecular imaging in order to reconstruct past environmental conditions and ecosystem variations at unprecedented spatial and thus temporal resolution. Additionally we will study the spatial distribution of biomarkers representing active microbial communities in sedimentary matrices on micrometer-scales in order to glean information on their relationship with geochemical processes. The project touches multiple themes of societal relevance: for example, one of our major objectives is to study annual to decadal scales climate variations in the late Pleistocene and in particular, the late Holocene. We want to determine the frequency and amplitudes of such variations and how marine and/or continental ecosystems responded. Such detailed information on past couplings of physical and biological processes is nearly impossible to obtain by traditional geochemical approaches. Our results will contribute to establish a baseline of natural climate and ecosystem variation prior to perturbation by human activity and likewise will provide new means for a more robust assessment of anthropogenic processes.

Work performed

In the first project period we have set up a dedicated laboratory for geobiomolecular imaging. This laboratory houses a Laser Desorption Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometer for molecular imaging of biomarkers in geological samples, a microscale X-Ray Fluorescence spectroscopy system for obtaining images of elemental composition of the same samples and with similar spatial resolution, and laboratory periphery for preparation and pre-treatment of samples. We have completed the method development required for preparing thin slices of sediment for analysis without disturbing the spatial integrity of the sample, established protocols for applying various chemical matrices that enable or enhance detection of our target analytes, and greatly expanded the set of compounds amenable to laser-based analysis in sedimentary matrices. We now have protocols in place for compounds covering a wide polarity range, from n-alkanes to highly functionalized polar lipids. These compounds include pigments, membrane lipids, cuticular waxes of higher land plants, bacterial and archaeal biomarkers, steroids and paleotemperature proxies. In combination, these compounds will aid in establishing rich datasets of past conditions at ultra-high temporal resolution. In addition, we have systematically studied the influence of mineral particles and organic matter coatings on mineral surfaces on the detectability of biomarker compounds. After demonstrating reproducibility of results in different vertical slices of the same sediment core, we have started to construct the first records of marine environmental changes in sediment archives from the Santa Barbara Basin and the Cariaco Basin and are now ready to establish meter-scale long records of micrometer-scales variations of biomarker distribution, translating into thousand-year-long records of monthly to annual environmental variation.

Final results

Work in the previous project period has vastly expanded the horizon for sediment mass spectrometry imaging. At the beginning of the ZOOMECULAR project, we had proof of concept that selected archaeal biomarkers could be detected in sediments and that meaningful variations in their distribution were observable by this technology. At this stage, we have fulfilled our main objectives and set the stage for systematic interrogation of geological samples with the goal to study past high-frequency environmental changes at unprecedented level of detail and resolution. Due to several innovations in the area of compound detection and sample preparation, our project goals will go beyond the ones originally stated in the proposal. Our results may have impact on several areas of the natural sciences, including geochemistry, (paleo)climatology, biogeochemistry and ecology. We have transferred a technology widely used in the medical and life sciences to readiness for applications in the geosciences, where diverse and rich sets of scientific problems await to be solved.