Innovative method opens up new perspectives for reconstructing climatic conditions of past eras
FRANKFURT. Corals and cave carbonates are important archives of past climate. This is because the composition of these carbonate deposits can reveal the temperatures that prevailed at the Earth’s surface at the time they formed. An international team of geoscientists led by Goethe University Frankfurt, Germany, has now developed a new method that makes it possible to identify whether the composition of these deposits was exclusively controlled by temperature, or if the formation process itself exerted an additional control. The new method allows scientists to determine past Earth surface temperatures more reliably and to study the processes involved in calcareous skeleton formation of modern and extinct species. (Nature Communications, DOI 10.1038/s41467-020-17501-0)
Corals precipitate their calcareous skeletons
(calcium carbonate) from seawater. Over thousands of years, vast coral reefs
form due to the deposition of this calcium carbonate. During precipitation,
corals prefer carbonate groups containing specific variants of oxygen (chemical
symbol: O). For example, the lower the water temperature, the higher the
abundance of a heavy oxygen variant, known as isotope 18O, within
the precipitated carbonate. Unfortunately, the 18O abundance of the
seawater also influences the abundance of 18O in the calcium
carbonate – and the contribution of 18O from seawater cannot be
resolved when determining temperatures based on carbonate 18O
A great step forward was the discovery that the isotopic composition of the precipitated carbonate allows temperature determinations independent of the composition of the water if the abundance of a specific, very rare carbonate group is measured. This carbonate group contains two heavy isotopes, a heavy carbon isotope (13C) and a heavy oxygen isotope (18O) which are referred to as “clumped isotopes”. Clumped isotopes are more abundant at lower temperatures.
However, even with this method there was still a problem: The mineralization process itself can affect the incorporation of heavy isotopes in the calcium carbonate (kinetic effects). If unidentified, the bias introduced by such kinetic effects leads to inaccurate temperature determinations. This particularly applies for climatic archives like corals and cave carbonates.
An international research group led by Professor Jens Fiebig at the Department of Geosciences at Goethe University Frankfurt has now found a solution to this problem. They have developed a highly sensitive method by which – in addition to the carbonate group containing 13C and 18O – the abundance of another, even rarer carbonate group can be determined with very high precision. This group also contains two heavy isotopes, namely two heavy oxygen isotopes (18O).
If the theoretical abundances of these two rare carbonate groups are plotted against each other in a graph, the influence of the temperature is represented by a straight line. If, for a given sample, the measured abundances of the two heavy carbonate groups produce a point away from the straight line, this deviation is due to the influence of the mineralization process.
David Bajnai, Fiebig’s former PhD student, applied this method to various climatic archives. Among others, he examined various coral species, cave carbonates and the fossil skeleton of a squid-like cephalopod (belemnite).
Today, Dr. Bajnai is a post-doctoral researcher at the University of Cologne. He explains: “We were able to show that – in addition to temperature – the mechanisms of mineralization also greatly affect the composition of many of the carbonates that we examined. In the case of cave carbonates and corals, the observed deviations from the exclusive temperature control confirm model calculations of the respective mineralization processes conducted by Dr. Weifu Guo, our collaborator at the Woods Hole Oceanographic Institution in the USA. The new method, for the first time, makes it possible to quantitatively assess the influence of the mineralization process itself. This way, the exact temperature of carbonate formation can be determined.”
Professor Jens Fiebig is convinced that the new method holds great potential: “We will further validate our new method and identify climatic archives that are particularly suitable for an accurate and highly precise reconstruction of past Earth surface temperatures. We also intend to use our method to study the effect that anthropogenic ocean acidification has on carbonate mineralization, for instance in corals. The new method might even allow us to estimate the pH values of earlier oceans.” If all this succeeds, the reconstruction of environmental conditions that prevailed throughout Earth’s history could be greatly improved, he adds.
Publication: David Bajnai, Weifu Guo, Christoph Spötl, Tyler B. Coplen, Katharina Methner, Niklas
Löffler, Emilija Krsnik, Eberhard Gischler, Maximilian Hansen, Daniela Henkel, Gregory D. Price, Jacek Raddatz, Denis Scholz, Jens Fiebig: Dual clumped isotope thermometry resolves kinetic biases in carbonate formation temperatures, Nature Communications, DOI 10.1038/s41467-020-17501-0, http://www.nature.com/ncomms
Professor Jens Fiebig
Department of Geosciences
Goethe University Frankfurt
Tel.: +49 (0) 69 798 40182
Dr. David Bajnai
Institute of Geology and Mineralogy
University of Cologne
Tel.: +49 (0)221 470 89829
How microbes in the primordial atmosphere obtained energy without oxygen
Iron transport protein is upregulated in SARS-CoV-2 infected cells
FRANKFURT. The Institute of Medical Virology at Goethe-University, Frankfurt am Main, Germany, and the University of Kent’s School of Biosciences (UK) have identified that a glycoprotein known as transferrin may critically contribute to severe forms of COVID-19.
SARS-CoV-2 is the coronavirus that causes COVID-19. It is currently not known why some individuals develop only mild or no symptoms when infected, whilst others experience severe, life-threatening forms of the disease. However, it is known that the risk of COVID-19 becoming severe increases with age and is higher in males than in females. Many severe COVID-19 cases are characterised by increased blood clotting and thrombosis formation.
The team combined existing data on gene expression in humans with cell culture research of SARS-CoV-2-infected cells to search for molecules involved in blood coagulation that differ between females and males, change with age, and are regulated in response to SARS-CoV-2 infection.
Out of more than 200 candidate factors, researchers identified a glycoprotein called transferrin to be a procoagulant (a cause of blood clotting) that increases with age, is higher in males than in females, and is higher in SARS-CoV-2-infected cells. Hence, transferrin may have potential as a biomarker for the early identification of COVID-19 patients at high risk of severe disease.
Publication: Katie-May McLaughlin, Marco Bechtel, Denisa Bojkova, Christian Münch, Sandra Ciesek, Mark N. Wass, Martin Michaelis, Jindrich Cinatl, Jr.: COVID-19-Related Coagulopathy - Is Transferrin a Missing Link? Diagnostics 2020, 10(8), 539; https://doi.org/10.3390/diagnostics10080539
Prof. Dr. rer. nat. Jindrich Cinatl
Institute for Medical Virology
University Hospital Frankfurt
Tel.: +49 69 6301-6409
Frankfurt scientists identify possible Achilles’ heel of SARS-CoV-2 virus
Geoscientists from Goethe University create sedimentary archive with annual resolution