Preprints
https://doi.org/10.5194/bg-2020-428
https://doi.org/10.5194/bg-2020-428

  24 Nov 2020

24 Nov 2020

Review status: a revised version of this preprint is currently under review for the journal BG.

Development of global temperature and pH calibrations based on bacterial 3-hydroxy fatty acids in soils

Pierre Véquaud1, Sylvie Derenne1, Alexandre Thibault2, Christelle Anquetil1, Giuliano Bonanomi3, Sylvie Collin1, Sergio Contreras4, Andrew Nottingham5, Pierre Sabatier6, Norma Salinas7, Wesley Philip Scott8, Josef P. Werne8, and Arnaud Huguet1 Pierre Véquaud et al.
  • 1Sorbonne Université, CNRS, EPHE, PSL, UMR METIS, Paris, 75005, France
  • 2Antea Group, Innovation Hub, 803 boulevard Duhamel du Monceau, Olivet, 45160, France
  • 3Dipartimento di Agraria, Università di Napoli Federico II, via Università 100, Portici, NA, 80055, Italy
  • 4Laboratorio de Ciencias Ambientales (LACA), Departamento de Química Ambiental, Facultad de Ciencias & Centro de Investigación en Biodiversidad y Ambientes Sustentables (CIBAS), Universidad Católica de la Santísima Concepción, Casilla 297, Concepción, Chile
  • 5School of Geosciences, University of Edinburgh, Crew Building, Kings Buildings, Edinburgh EH9 3FF United Kingdom
  • 6Univ. Savoie Mont Blanc, CNRS, EDYTEM, Le Bourget du Lac, 73776, France
  • 7Instituto de Ciencias de la Naturaleza, Territorio y Energías Renovables, Pontificia Universidad Catolica del Peru, Av. Universitaria 1801, San Miguel, Lima 32, Peru
  • 8Department of Geology and Environmental Science, University of Pittsburgh, Pittsburgh, PA 15260, USA

Abstract. 3-hydroxy fatty acids (3-OH FAs) with 10 to 18 C atoms are membrane lipids mainly produced by Gram-negative bacteria. They have been recently proposed as temperature and pH proxies in terrestrial settings. Nevertheless, the existing correlations between pH/temperature and indices derived from 3-OH FA distribution (RIAN, RAN15 and RAN17) are based on a small soil dataset (ca. 70 samples) and only applicable regionally. The aim of this study was to investigate the applicability of 3-OH FAs as mean annual air temperature (MAAT) and pH proxies at the global level. This was achieved using an extended soil dataset of 168 topsoils distributed worldwide, covering a wide range of temperatures (5 °C to 30 °C) and pH (3 to 8). The response of 3-OH FAs to temperature and pH was compared to that of established branched GDGT-based proxies (MBT'5Me/CBT). Strong linear relationships between 3-OH FA-derived indices (RAN15, RAN17 and RIAN) and MAAT/pH could only be obtained locally, for some of the individual transects. This suggests that these indices cannot be used as paleoproxies at the global scale using simple linear regression models, in contrast with the MBT'5Me and CBT. However, strong global correlations between 3-OH FA relative abundances and MAAT/pH were shown by using other algorithms (multiple linear regression, k-NN and random forest models). The applicability of the k-NN and random forest models for paleotemperature reconstruction was tested and compared with the MAAT record from a Chinese speleothem. The calibration based on the random forest model appeared to be the most robust. It showed similar trends with previously available records and highlighted known climatic events poorly visible when using local 3-OH FA calibrations. Altogether, these results demonstrate the potential of 3-OH FAs as paleoproxies in terrestrial settings.

Pierre Véquaud et al.

 
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

Pierre Véquaud et al.

Pierre Véquaud et al.

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Short summary
A better understanding of past climate variations is essential to apprehend future climatic changes. Most of the available paleoenvironmental proxies were developed and used in oceanic environments. Nevertheless, it is essential to have reliable proxies which can be applied to continental archives. The aim of this study is to investigate the applicability of specific organic compounds, 3-hydroxy fatty acids, as temperature and pH proxies at the global level using an extended soil dataset.
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