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Membrane lipids of soil bacteria as recorders of past climatic changes

On 15 September 2011 Francien Peterse will defend  her thesis 'Environmental controls on the distribution of bacterial tetraether membrane lipids: Constraints on the MBT-CBT paleothermometer'.


Branched glycerol dialkyl glycerol tetraethers (GDGTs) are membrane lipids of as of yet unknown bacteria that adapt the structure of their membranes to changes in their living environment. An empirical study showed that their distribution in soils worldwide is mainly determined by mean annual air temperature and soil pH. Hence, based on the distribution of branched GDGTs in old soils or coastal marine sediments, past continental air temperatures can be reconstructed. Although this method shows a lot of promise to obtain information on past continental climate change, its validity and applicability needs further testing.

The influence of temperature, for example, was tested by analyzing the distribution of branched GDGTs in geothermally heated soils surrounding hot springs, as well as along an altitude transect, where air temperature decreases with increasing altitude. These tests showed that changes in temperature are indeed reflected in the distribution of branched GDGTs.

After testing, the method was applied on a loess-paleosol sequence from the loess plateau in China. This resulted in a temperature reconstruction covering the last 34,000 year, and showed that the onset of atmospheric warming and the intensification of the summer monsoon were decoupled over the last deglaciation.

Although these results show that branched GDGTs are a suitable tool to reconstruct past climatic changes, care must be taken in interpreting the absolute temperatures that are generated with this method.