Greenhouse gas production and lipid biomarker distribution in Yedoma and Alas thermokarst lake sediments in Eastern Siberia

Permafrost thaw leads to thermokarst lake formation and talik growth tens of meters deep, enabling microbial decomposition formerly frozen organic matter (OM). We analyzed two 17-m-long sediment cores taken in Central Yakutia, Russia. One core was from an Alas a Holocene basin that underwent multiple generations, the second young Yedoma upland (formed ~70 years ago) whose sediments have thawed for first time since deposition. This comparison provides glance into OM fate thawing deposits. total carbon (TOC) dissolved (DOC) content, n-alkane concentrations, bacterial archaeal membrane markers. Furthermore, we conducted 1-year-long incubations (4°C, dark) measured anaerobic dioxide (CO2) methane (CH4) production. The both contained little TOC (0.7 ± 0.4 wt%), but DOC values were relatively high, with highest (1620 mg L−1). Cumulative greenhouse gas (GHG) production after 1 year (226 212 µg CO2-C g−1 dw, 28 36 CH4-C dw) 3 1.5 times lower sediments, respectively (75 76 19 29 dw). CO2 likely results readily bioavailable OM, while CH4 non-frozen top this suggests methanogenic communities established upon thaw. GHG resulted advanced during development. found drivers differ following Our suggest TOC-poor mineral deposits, which are widespread throughout Arctic, can be substantial. Therefore, our novel data relevant vast ice-rich permafrost deposits vulnerable formation.