Read the fine print: Zooming into paleoenvironmental and biogeochemical processes through molecular imaging of biomarker distributions in sediments

Periodic Reporting for period 4 - ZOOMecular (Read the fine print: Zooming into paleoenvironmental and biogeochemical processes through molecular imaging of biomarker distributions in sediments)

Okres sprawozdawczy: 2020-05-01 do 2021-04-30

A major challenge of high societal relevance is to assess the future effects of ongoing climate change. Records of past climate, including events of abrupt change and past warm worlds, are useful analogues in this regard. Molecular biomarkers, i.e. organic molecules in geological samples that can be traced back to a biological origin, carry taxonomic information on source organisms and can record conditions prevailing in their habitat. When such biomarkers are preserved in marine or lacustrine sediments, they can be used as proxies for the reconstruction of physical, chemical and biological parameters in paleoenvironments. In sedimentary archives with established age models, this proxy information is used to generate records of past climate and environmental change.
Conventional biomarker analyses require relatively large samples, which limits the temporal resolution of reconstructions. Even at locations with high sedimentation rates, samples will integrate information of decades to centuries. The groundbreaking goal of the ZOOMECULAR project was to enable and apply ultra-high-resolution biomarker analysis to the investigation of suitable climate archives, and to obtain paleoenvironmental records with unprecedented temporal resolution.
In the framework of the project, we have established the Geobiomolecular Imaging Laboratory at the University of Bremen (Germany) as the sole facility worldwide dedicated to micrometer-resolution biomarker analysis in geological samples. A transformative approach to molecular biomarker analysis has been implemented, including the development of methods for the preparation of samples, the spatially resolved analysis of molecular biomarkers, and the evaluation and visualization of obtained maps of biomarker distributions.
After implementation and method development, we have intensively worked on varved sediment cores with well-established age models. We have demonstrated that in these archives, sub-annual variability of properties such as sea surface temperature, redox condition, and upwelling intensity can be reconstructed. In recent sediments, this allowed us to compare proxy signatures to instrumental records, and thus to better understand the information they store. In older sediments, ultra-high-resolution molecular proxy records inform on seasonal to decadal variability associated to past warm worlds or to events of abrupt climate change, and can track the sequence of climate and environmental change during such events. As a result, our understanding of climate variability on timescales relevant from the human and ecosystem perspective will be greatly enhanced.

The first task was to establish the Geobiomolecular Imaging Laboratory at the University of Bremen (https://www.marum.de/en/about-us/HinrichsLab-Geobiomolecular-Imaging-Laboratory.html). A new lab was built to house an ultra-high-resolution mass spectrometer, the analytical centerpiece, a micro X-Ray Fluorescence system, and infrastructure for sample preparation. This task was completed efficiently so that routine operation of the facility could start a few months after the beginning of the project.
Initially, the main resources were devoted towards establishing methods for ultra-high-resolution biomarker analysis. At that stage, we had only completed one proof of concept study that introduced mass spectrometry imaging (MSI) of molecular proxies using instrumentation from the manufacturer (Wörmer et al., PNAS, 2014), but protocols for sample preparation were lacking. This goal was addressed in work package (WP) 1, the analytical backbone of the project, and WP5, which dealt with data processing. Development of methods was more complex than anticipated, especially regarding (1) preparation of samples to ensure high sensitivity and unaltered spatial distribution of the analytes and (2) the quality control, evaluation and visualization of the complex datasets, which consist of 2D maps of a vast number of mass spectra. Three published papers (Alfken et al., 2019; Wörmer et al., 2019; Alfken et al., 2020) addressed these issues and laid the groundwork for subsequent applications of the approach to geological archives. As a result of the extensive method developments, progress on the scientific interrogation of geological archives was not as rapid as initially projected.
In subsequent applications to environmental samples, micrometer scale mapping of proxies led to previously inaccessible observations. In recent sediments, comparison of MSI data to the instrumental record provided clues on mechanisms of sedimentary proxy formation (WP2). We investigated the variability of molecular proxies for sea surface temperatures (SST) with sub-annual resolution and demonstrated that MSI resolves seasonal SST fluctuations, but also showed that varying nutrient concentrations influence the amplitude of the SST signal (Alfken et al., 2020).
In older sedimentary archives, MSI allows to reconstruct climate and ecosystem variability at ultra-high resolution beyond the instrumental record. This ability is the core of WP3 and was the major focus during the last years of the project. We have published new insights regarding the mechanisms that caused the delay in cooling of Western Europe relative to the Arctic into the Younger Dryas (Obreht et al., 2020). Additionally, a number of manuscripts are close to submission or currently being revised that deal with the magnitude of decadal climate change during the last interglacial as compared to current and predicted future warming, the changes of intra- to interannual climate variability at the onset of the Holocene, and the interplay of combustion events, soil erosion and eutrophication preceding the Permian Triassic Mass Extinction.
In contrast to the fossil biomarkers used to reconstruct paleoenvironments, labile biomolecules are used in biogeochemical studies to track microbes and their actions in modern environments (WP4). By mapping biomarkers in microbial mats from hydrothermal springs, we learned how these communities are spatially structured, and how they respond to micrometer scale environmental gradients (Wörmer et al., 2020).
At this point, we have published five papers, and another seven are at advanced stages of preparation or revision. 11 undergraduate students carried out their MSc or BSc thesis work in the context of the project. The project enabled team members to significantly advance in their careers advances and follow-up funding has been generated that supports the operation of the scientific infrastructure and secures the retention of core personnel as well as further development of our approach to full maturity at an intensity level comparable to the ERC project.

The ZOOMecular project has improved the resolution of molecular proxy records by orders of magnitude and thereby redefined the state of the art in high resolution paleoclimate reconstruction in sedimentary archives.
Being able to routinely generate paleoclimate and paleoenvironmental records with µm-resolution, and to track sub-annual variability, has to be considered a major breakthrough in the geosciences.
The real impact of the ZOOMecular project will be fully visible in the next years, when paleoclimate records with unprecedented resolution will have been published that inform on environmental changes at the seasonal to decadal timescales, i.e. those timescales most relevant from the human perspective.

Grafical abstract of ZOOMecular

Periodic Reporting for period 4 - ZOOMecular (Read the fine print: Zooming into paleoenvironmental and biogeochemical processes through molecular imaging of biomarker distributions in sediments)

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