Introducing global peat-specific temperature pH calibrations based on brGDGT bacterial lipids

Naafs, B D and Inglis, G N and Zheng, Y and Amesbury, J and Biester, H and Bindler, R and Blewett, J and Burrows, M A and del Castillo Torres, D and Chambers, Frank M and Cohen, A D and Evershed, R P and Feakins, S J and Gallego-Sala, A and Grandois, L and Gray, D M and Hatcher, P G and Honorio Coronado, E N and Hughes, P D and Huguet, A and Könönen, M and Laggoun-Défarge, F and Lähteenoja, O and Marchant, R and McClymont, E and Pontevedra-Pombal, X and Ponton, C and Pourmand, A and Rizzuti, A M and Rochefort, L and Schellekens, J and De Vleeschouwer, F and Pancost, R D (2017) Introducing global peat-specific temperature pH calibrations based on brGDGT bacterial lipids. Geochimica et Cosmochimica Acta, 208. pp. 285-301. ISSN 0016-7037

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Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane-spanning lipids from Bacteria and Archaea that are ubiquitous in a range of natural archives and especially abundant in peat. Previous work demonstrated that the distribution of bacterial branched GDGTs (brGDGTs) in mineral soils is correlated to environmental factors such as mean annual air temperature (MAAT) and soil pH. However, the influence of these parameters on brGDGT distributions in peat is largely unknown. Here we investigate the distribution of brGDGTs in 470 samples from 96 peatlands around the world with a broad mean annual air temperature (−8 to 27 °C) and pH (3–8) range and present the first peat-specific brGDGT-based temperature and pH calibrations. Our results demonstrate that the degree of cyclisation of brGDGTs in peat is positively correlated with pH, pH = 2.49 x CBTpeat + 8.07 (n = 51, R2 65 = 0.58, RMSE = 0.8) and the degree of methylation of brGDGTs is positively correlated with MAAT, MAATpeat (°C) = 52.18 x MBT5me’ – 23.05 (n = 96, R2 67 = 0.76, RMSE = 4.7 °C).These peat-specific calibrations a 68 re distinct from the available mineral soil 69 calibrations. In light of the error in the temperature calibration (~ 4.7 °C), we urge caution in any application to reconstruct late Holocene climate variability, where the climatic signals are relatively small, and the duration of excursions could be brief.Instead, these proxies are well-suited to reconstruct large amplitude, longer-term shifts in climate such as deglacial transitions. Indeed, when applied to a peat deposit spanning the late glacial period (~15.2 kyr), we demonstrate that MAATpeat yields absolute temperatures and relative temperature changes that are consistent with those from other proxies. In addition, the application of MAATpeat to fossil peat (i.e.lignites) has the potential to reconstruct terrestrial climate during the Cenozoic. We conclude that there is clear potential to use brGDGTs in peats and lignites to reconstruct past terrestrial climate.

Item Type: Article
Article Type: Article
Uncontrolled Keywords: GDGT, biomarker, peatland, calibration, lignite
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Divisions: Schools and Research Institutes > School of Natural & Social Sciences > Environmental Sciences
Research Priority Areas: Environmental Dynamics & Governance
Depositing User: Anne Pengelly
Date Deposited: 16 Jan 2017 15:33
Last Modified: 12 May 2017 08:07

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