Warmed Icelandic Soils, Lipids and Sequencing: towards a better understood climate proxy (2016 - 2018)
Researcher: Cindy De Jonge
Chemical fossils are molecular components that carry information on the environment in which they were produced, sometimes millions of years ago. The distribution of a group of 15 membrane lipids in soils, for instance, depends on the temperature and pH of the soils in which these organisms are living. They are conserved in several types of geological archives (marine sediments, lake sediments, soils) and their distribution has been used to reconstruct changes in the temperature of the past. However, even the most recent temperature calibration is not accurate enough to reconstruct absolute temperatures.
In this research project we aim to improve this thermometer of the past, with geochemical and microbiological research. Firstly, the branched tetraethers that are currently used in the existing climate proxies will be measured in soils, together with their precursor compounds, their building blocks. These components will be measured in a set of Icelandic soils that are warmed by thermal water, and thus show a gradient in temperature. As these soils have been studied extensively in the framework of the Forhot project (www.forhot.is), the lipid distribution can be linked directly to the in-situ measured temperature.
Following up on this, the patterns that are recognized on a local scale will be tested on a larger spatial scale. For this purpose, soil that have been studied in the framework of the EU ICOS project (www.icos-ri.eu) will be used, as they cover the different European ecosystems and soil types.
Previous studies have indicated that Acidobacteria are probably the source organisms of the branched tetraether lipids, but only 1 of the 15 compounds that are frequently encountered in soils, has been recovered from an Acidobacterial culture. To shed light on the abundance and variability of the source organisms in soils, the bacterial diversity along the local temperature gradient (Forhot soils) will be analyzed with Illumina MiSeq technology. This diversity and its dependence on soil temperature will also be studied on a larger spatial scale (ICOS soils).
This research will allow to gain a better insight in the environmental factors that influence the bacterial source organisms. This understanding will improve the accuracy and interpretation of the thermometer for the temperature in the past.