BRIDGE Seminar

Professor Ann Pearson: Lipids of marine Archaea – a new paleobarometer for pCO2?

Marine planktonic Thaumarchaeota oxidize ammonia and fix inorganic carbon to biomass.  The pathway for carbon fixation in these taxa is known as the 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB) pathway, and unique among all known autotrophic carbon metabolisms, this pathway exclusively uses HCO₃^-, rather than CO₂, as the substrate for carbon fixation.  To date it has been assumed that growth in the ocean at pH ≥7.5 (high [HCO₃^-]) necessarily implies that Thaumarchaeota are never carbon-limited.  However, recently we measured carbon isotope ratios (d¹³C) of archaeal lipids (GDGTs) in a marine water column transect, showing that the expressed isotope effect (e) scales directly with dissolved CO₂ concentrations, implying that d¹³C_GDGT values hold promise as a pCO₂ paleobarometer.  The same relationship appears to hold also with a limited set of modern sediment core-tops.  Sensitivity of this new proxy is similar to other geochemical methods such as boron isotopes and the alkenone paleobarometer, although additional calibration and testing is needed.   

This seminar is given by Prof. Ann Pearson (Harvard University) who is currently in Bristol as a visiting professor, working with Fanny Monteiro and Rich Pancost (https://www.bristol.ac.uk/ias/fellowships/meakers/pearson.html/#d.en.378670). 

Please note that the BRIDGE Earth System modelling group discussion will take place in SR1 at 1pm after this seminar. 

Please note this seminar is only open to University of Bristol Staff and Students.