In:
Biogeosciences, Copernicus GmbH, Vol. 18, No. 12 ( 2021-07-01), p. 3937-3959
Abstract:
Abstract. Gram-negative bacteria produce specific membrane lipids, i.e. 3-hydroxy fatty acids with 10 to 18 C atoms. They have
been recently proposed as temperature and pH proxies in terrestrial
settings. Nevertheless, the existing correlations between pH or temperature and
indices derived from 3-OH FA distribution
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
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 glycerol dialkyl glycerol tetraether (GDGT)-based proxies
(MBT'5Me/CBT). Strong linear relationships between 3-OH-FA-derived
indices (RAN15, RAN17 and RIAN) and MAAT or pH could only be
obtained locally for some of the individual transects. This suggests that
these indices cannot be used as palaeoproxies 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 or pH were shown by using other algorithms (multiple linear regression,
k-NN and random forest models). The applicability of the three
aforementioned models for palaeotemperature 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
generally 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 palaeoproxies in terrestrial settings.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-18-3937-2021
DOI:
10.5194/bg-18-3937-2021-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2021
detail.hit.zdb_id:
2158181-2
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