ALBERT

Description: This dataset provides glycerol dialkyl glycerol tetraethers (GDGTs) concentrations for the Lateglacial sediment sequence retrieved from Lake Hämelsee (Germany) in 2013. GDGTs concentrations (ng/g) are presented against both depth (m) and age (cal yr. BP). The GDGTs dataset was used to calculate the GDGT-0/crenarchaeol ratio, which was interpreted to represent lake water oxygenation, which, given the local settings, was likely driven by changes in windiness. Additionally, the GDGT dataset was used to calculate the degree of methylation of 5-methyl brGDGTs (MBT'5me), which can be used to reconstruct past temperature change through translation MBT'5me into mean temperature of the months above freezing. As such, the GDGT data provides information on LGIT climate dynamics at lake Hämelsee. Of the 167 samples used for lipid extraction (see https://doi.pangaea.de/10.1594/PANGAEA.964524), the alcohol/fatty acid fraction of 94 samples was further processed to analyse glycerol dialkyl glycerol tetraethers (GDGTs), which are membrane lipids of certain archaea and bacteria (Schouten et al., 2013). In short, a known amount of internal standard was added to each fraction, which was then redissolved in hexane:isopropanol 99:1 and passed over a 0.45 µm PTFE filter prior to injection on a Agilent 1260 Infinity ultra-high performance liquid chromatograph coupled to an Agilent 6130 single quadrupole mass spectrometer following the settings and elution protocol of Hopmans et al. (2016). A minimum peak area of 3000 and a signal-to-noise ratio of 〉3 was maintained as detection limit. Quantification of the GDGTs is based on the assumption that the mass spectrometer equally responds to the GDGTs and the internal standard. All analyses were performed in the laboratories of Utrecht University, the Netherlands.