Archaeal lipids reveal climate‐driven changes in microbial ecology at Lake El'gygytgyn (Far East Russia) during the Plio‐Pleistocene

Abstract

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.

Biomarker proxy records of Arctic climate change during the Mid-Pleistocene transition from Lake El'gygytgyn (Far East Russia)

“…The high GDGT-0 / crenarchaeol ratio (average 68.8), as well as the fact that many samples did not contain all of the iGDGTs required to calculate a TEX 86 value, precludes the use of the TEX 86 paleothermometer (Schouten et al, 2002) at Lake El'gygytgyn. This result is consistent with prior investigations of different time intervals of the Lake El'gygytgyn record (D'Anjou et al, 2013;Holland et al, 2013;de Wet et al, 2016;Keisling et al, 2017;Daniels et al, 2021).…”

“…The lack of MPT cooling at El'gygytgyn is difficult to explain given the expansion of Northern Hemisphere ice sheets at that time. It could imply that the climate at the study site is not representative of the pan-Arctic region, and indeed, there is considerable spatial variability in climate change across the Arctic (Daniels et al, 2021;Tulenko et al, 2020). Alternatively, it may sug-gest that Arctic cooling was not the critical driver of intensified ice sheet growth, implicating a strong role for the regolith removal hypothesis (Clark and Pollard, 1998;Yehudai et al, 2021) or Southern Hemisphere (i.e., Antarctic) cooling and ice sheet expansion (Ford and Raymo, 2020).…”

“…Lake El'gygytgyn sediments are dominated by brGDGTs with only small concentrations of iGDGTs present (Fig. S4 in the Supplement) (Holland et al, 2013;D'Anjou et al, 2013;de Wet et al, 2016;Keisling et al, 2017;Daniels et al, 2021). Thus, we use the methylation of branched tetraethers index (Eq.…”

Lake Dynamics Modulate the Air Temperature Variability Recorded by Sedimentary Aquatic Biomarkers: A Holocene Case Study From Western Greenland

“…Caldarchaeol (GDGT-0) and crenarchaeol (GDGT-4) are the most abundant isoGDGTs, with mean fractional abundances of 0.79 ± 0.13 and 0.14 ± 0.12 (Figure S3b in Supporting Information S1), similar to sediments of other Arctic lakes (Daniels et al, 2021). Caldarchaeol is more abundant than crenarchaeol in all samples, although it decreases in absolute and relative abundances in step with an increase in crenarchaeol in the mid-Holocene.…”

Quaternary environmental and climatic history of the northern high latitudes – recent contributions and perspectives from lake sediment records

“…Wennrich et al, 2016, and references therein). In this volume, Daniels et al (2022) present a new molecular biomarker data set that extends throughout the entire core (Table 1). The data reveal that the TEX 86 index, which is often used as an organic palaeothermometer, in Lake El'gygytgyn is strongly influenced by non-temperature factors, in particular, archaeal community changes.…”