Isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs) are commonly preserved molecular biomarkers of archaea whose distributions can be used to reconstruct past temperature, and possibly, methane and nitrogen cycling. To date, iGDGT systematics have not been widely investigated in Arctic lacustrine environments. Here, we analyze iGDGTs in sediments of Lake El'gygytgyn, located in the Russian Arctic, to reconstruct the paleoenvironmental conditions from the Pliocene to today using TEX86 and other indices. The TEX86-inferred temperature history shows a long-term warming trend, in stark contrast to other Arctic records and other proxies from Lake El'gygytgyn, suggesting that non-temperature factors obfuscate the use of TEX86 at this site. Other GDGT-based indices including the BIT Index, ΔRing Index, Methane Index and the GDGT-0/crenarchaeol ratio suggest that TEX86 is strongly influenced by archaeal community changes. The most significant community shifts are observed c. 2.4 Ma and record an increase in Euryarchaeota production and/or a decrease in Thaumarchaeota production, which was driven by the establishment of permafrost and perennial lake ice during the early Pleistocene. Overall, this study demonstrates an important interpretative framework for iGDGTs in lacustrine systems and describes variations in Arctic climate and lake biogeochemistry over timescales of thousands to millions of years. © 2021 John Wiley & Sons, Ltd.
Bibliographical noteFunding Information:
This work was supported by the Lake El'gygytgyn Drilling Project, an international collaboration and the National Science Foundation, grant no. 1204087. We thank Martin Melles and Volker Wennrich for providing bulk geochemical data and for useful discussions about Lake El'gygytgyn. We thank Dr Stephanie Kusch and an anonymous reviewer for insightful comments that helped improve the manuscript. We further thank the numerous UMass Amherst graduate and undergraduate students who have contributed to the organic geochemical analyses of Lake El'gygytgyn samples including Thomas Barrasso, Julie Chessia, Kayley Donze, Joanne Johnson, Stephen Lukas, Nicholas Lyons, Daniel Miller, Victoria Phu, Geoffrey Small, Rebecca A. Smith, Meghan Thompson‐Munson and Ben Urann. We thank Anders Noren, Kristina Brady and the staff at LacCore for their assistance and support with numerous large sample requests. We also are grateful to John Sweeney for technical support.
© 2021 John Wiley & Sons, Ltd.
- isoprenoid glycerol dialkyl glycerol tetraethers
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