Isotopic and GDGTs analysis of methane-related biological processes (methane production and oxidation) in a Miocene sedimentary pool

Methane is one of the most important greenhouse gases. A substantial proportion of this gas originates from marine environments where both its biological formation and oxidation occur. Variations in seawater properties due to climatic perturbations are likely to be reflected in the living conditions of both methanotrophic and methanogenic microbiota. The debate about the fate of the marine methane cycle facing global change may benefit from the inclusion of data concerning marine palaeoenvironments, especially salt-bearing sediments, which are a relic of the evaporitic sea. The study presents a GDGT-derived palaeorecord of methane-related biological processes in Miocene Wieliczka Formation sediments (a remnant of the Paratethys sea) as well as a description of present-day microbial communities subsisting in evaporates using  activity measurements and high throughput sequencing. The results revealed that GDGT-based indices corresponded with the reconstructed sedimentary conditions and microbial ecophysiology which confirms their applicability of reconstruction for biological methane formation and oxidation in saline environments.