Bacterial GDGTs in Holocene sediments and catchment soils of a high-alpine lake: application of the MBT/CBT-paleothermometer

Abstract

A novel proxy for continental mean annual air temperature (MAAT) and soil-pH, the MBT/CBT-paleothermometer, is based on the temperature (<i>T</i>) and pH-dependent distribution of specific bacterial membrane lipids (branched glycerol dialkyl glycerol tetraethers – GDGTs) in soil organic matter. Here, we tested the applicability of the MBT/CBT-paleothermometer to sediments from Lake Cadagno, a small high-alpine lake in southern Switzerland with a small catchment of 2.4 km<sup>2</sup>. We analysed the distribution of bacterial GDGTs in catchment soils and in a radiocarbon-dated sediment core from the centre of the lake, covering the entire Holocene. The composition of bacterial GDGTs in soils are almost identical to that in the lake's surface sediments, indicating a common origin of the lipids. Consequently, their transfer from the soils into the sediment record is undisturbed, apparently without any significant alteration of their distribution through in situ production or early diagenesis of branched GDGTs. The MBT/CBT-inferred MAAT-estimates from soils and surface sediments are in good agreement with instrumental values for the Lake Cadagno region (~0.5 °C). Moreover, downcore MBT/CBT-derived MAAT-estimates match in timing and magnitude other proxy-based <i>T</i>-reconstructions from nearby locations for the last two millennia. Major climate anomalies recorded by the MBT/CBT-paleothermometer are, for instance, the Little Ice Age (~14th to 19th century) and the Medieval Warm Period (~10th to 14th century). Together, our observations confirm the applicability of the MBT/CBT-paleothermometer to Lake Cadagno sediments. Consistent with other <i>T</i>-records from both the Alps and from the subpolar NE-Atlantic, our lacustrine paleotemperature record indicates Holocene MAAT-variations with an apparent cyclicity of ~2 kyr. The good temporal match of the warm periods determined for the S-Alpine region with NW-European winter precipitation strength implies a strong and far-reaching influence of the North Atlantic Oscillation on continental European Holocene <i>T</i>-variations

Impact of riverine suspended particulate matter on the branched glycerol dialkyl glycerol tetraether composition of lakes: The outflow of the Selenga River in Lake Baikal (Russia)

“…Peterse et al, 2011), speleothems (Blyth and Schouten, 2013), lake sediments (e.g. Niemann et al, 2012), but initially in marine sediments (e.g. Weijers et al, 2007b;Bendle et al, 2010).…”

Glacial and Holocene terrestrial temperature variability in subtropical east Australia as inferred from branched GDGT distributions in a sediment core from Lake McKenzie

“…The MBT/CBT index from terrestrial soils has subsequently been used to estimate paleotemperatures in marine sediment cores from coastal regions (Rueda et al, 2009;Weijers et al, 2007a), and potentially be additionally used to reconstruct the paleotemperature from lacustrine sediment cores (e.g. Tierney et al, 2010;Niemann et al, 2012).…”

“…Although many studies observed that branched GDGTs are ubiquitously found in lake sediments (e.g. Niemann et al, 2012;Sinninghe Damsté et al, 2009;Tierney et al, 2010;Tyler et al, 2010), numerous studies have found evidence suggesting that branched GDGTs in the many lake sediments were not only derived from the surrounding soils. Instead, at least part of the branched GDGTs appear to have been produced within the water column or sediments of these lakes (Bechtel et al, 2010;Loomis et al, 2011;Sinninghe Damsté et al, 2009;Tierney and Russell, 2009;Tierney et al, 2012).…”

Sources of core and intact branched tetraether membrane lipids in the lacustrine environment: Anatomy of Lake Challa and its catchment, equatorial East Africa

“…Niemann et al 2012), differences in brGDGT distributions between lake sediments and adjacent terrestrial soils have now been observed at numerous sites, such as Lake Towuti, Indonesia (Tierney and Russell, 2009), several small lakes in western Uganda (Loomis et al, 2011), and a small pond in the US (Tierney et al, 2012). Using a relatively small soil dataset, Sinninghe reported this same discrepancy between soils and sediments at Lake Challa, and speculated that this may point to an additional source of brGDGTs either from outside the area then sampled for soils, or in the water column or sediments of Lake Challa, making it necessary to further constrain fluxes to the lake system.…”