@article{0da0e9da5dfb4063b55b61cfbcda519d,
title = "Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids",
abstract = "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 × CBTpeat + 8.07 (n = 51, R2 = 0.58, RMSE = 0.8) and the degree of methylation of brGDGTs is positively correlated with MAAT, MAATpeat (°C) = 52.18 × MBT5me′ − 23.05 (n = 96, R2 = 0.76, RMSE = 4.7 °C). These peat-specific calibrations are distinct from the available mineral soil 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.",
keywords = "Biomarker, Calibration, GDGT, Lignite, Peatland",
author = "Naafs, {B. D.A.} and Inglis, {G. N.} and Y. Zheng and Amesbury, {M. J.} and H. Biester and R. Bindler and J. Blewett and Burrows, {M. A.} and {del Castillo Torres}, D. and Chambers, {F. M.} and Cohen, {A. D.} and Evershed, {R. P.} and Feakins, {S. J.} and M. Ga{\l}ka and A. Gallego-Sala and L. Gandois and Gray, {D. M.} and Hatcher, {P. G.} and {Honorio Coronado}, {E. N.} and Hughes, {P. D.M.} and A. Huguet and M. K{\"o}n{\"o}nen and F. Laggoun-D{\'e}farge and O. L{\"a}hteenoja and M. Lamentowicz and R. Marchant and E. McClymont and X. Pontevedra-Pombal and C. Ponton and A. Pourmand and Rizzuti, {A. M.} and L. Rochefort and J. Schellekens and {De Vleeschouwer}, F. and Pancost, {R. D.}",
note = "Funding Information: We acknowledge support from Labex VOLTAIRE (ANR-10-LABX-100-01). Peat from Patagonia and Tierra del Fuego were collected thanks to a Young Researcher Grant of the Agence National de la Recherche (ANR) to FDV, project ANR-2011-JS56-006-01 ?PARAD? and with the help of Ramiro Lopez, Andrea Coronato and Veronica Pancotto (CADIC-CONICET, Ushuaia). Peat from Brazil was collected with the context of CNPq project 482815/2011-6. Samples from France (Frasne and La Guette) were collected thanks to the French Observatory of Peatlands. Samples from the French Pyr?n?es were obtained in the context of the LABEX DRIIHM ? OHM VICDESSOS program, while the GDRI Car-Wet-Sib II program funded the Siberian peat samples. The Tanzanian samples were collected in the framework of a ?CNRS INSU EC2CO project (2012-2013)? called ?Etude de lipides complexes (alkyl tetra?thers de glyc?rol) et de leurs microorganismes sources en milieu lacustre: cas du lac Masoko (Tanzanie)?. The Canadian peat was collected in the context of the NSERC-Discovery grant of L. Rochefort. Peats from China were obtained under a National Natural Science Foundation of China grant (No. 41372033), awarded to Y. Zheng. Samples from Poland were obtained using funding from the National Science Centre in Poland, grant no. DEC-2013/09/B/ST10/01589. Samples from Latvia were obtained in collaboration with the Latvian Peat Producer's Association and projects ETF9031, IUT 1-8 and EBOR. Thanks to Uldis Ozols for valuable support during the fieldwork. We thank the editor, 3 anonymous reviewers, and Jess Tierney for valuable comments. Publisher Copyright: {\textcopyright} 2017 The Authors",
year = "2017",
month = jul,
day = "1",
doi = "10.1016/j.gca.2017.01.038",
language = "English",
volume = "208",
pages = "285--301",
journal = "Geochimica et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier",
}