ISTerre seminar

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Unearthing ancient DNA from sediment archives: a journey from fire to ice

Wednesday 26 November 2025 - 11h00

Lucinda Duxbury - Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia
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Understanding how ecosystems have responded to past environmental changes is an important way we can contextualise the current climate crisis. Sedimentary archives can preserve nucleic acids over millions of years and thus represent a treasure trove of long-term records of past biodiversity. Despite this, the taphonomic processes governing their preservation in sediments are poorly understood. In this talk, I will discuss two well-preserved sedimentary ancient DNA records from opposite sides of the globe. The first comes from a small lake on Kangaroo Island/Karti, Australia, with a maximum depth of about one metre and high summer temperatures. Although conventional wisdom at the time suggested such a lake would be unfavourable to the preservation of DNA, we recovered sedimentary ancient DNA throughout the entire 7,000-year sequence. Our results helped to untangle local and regional signals of vegetation change in response to changes in climate, fire and people. The other record comes from an international collaborative effort to drill Arctic marine sediments down to 600 metres below the seafloor from water depths of over a kilometre. The expedition targeted sediments in the eastern Fram Strait, Arctic, with highly expanded deposition during past warm periods. We have so far successfully extracted sedimentary ancient DNA up to approximately half a million years old, including a high resolution record of marine ecosystem change from the transition into MIS 5e (~130-115 Ka), which by some estimates was the last time the Arctic was ice free in summer. Furthermore, we are attempting to extract DNA from 3-million-year-old sediment. In recent years, a link between the presence of certain clays and the preferential preservation of ancient DNA has been proposed. At ISTerre, I am conducting X-ray diffraction analysis to investigate the mineralogical properties of these Arctic sediments. We aim to link these results with indicators of DNA damage to interrogate the potential control of mineralogy on DNA preservation in the eastern Fram Strait.

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Organizing team : Minéralogie

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

Informations de visio :

Stanislav Jelavic is inviting you to a scheduled Zoom meeting.

Topic: Unearthing ancient DNA from sediment archives: a journey from fire to ice
Time: Nov 26, 2025 11:00 AM Paris
Join Zoom Meeting
https://univ-grenoble-alpes-fr.zoom.us/j/94964887683?pwd=0ja2VFZQcgKhNhKkoyIgfDvFt4lLxF.1