 |
| Titel |
Provenance of tetraether membrane lipids in a large temperate lake (Loch Lomond, UK): implications for glycerol dialkyl glycerol tetraether (GDGT)-based palaeothermometry |
| VerfasserIn |
L. K. Buckles, J. W. H. Weijers, X.-M. Tran, S. Waldron, J. S. Sinninghe Damsté |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 19 ; Nr. 11, no. 19 (2014-10-09), S.5539-5563 |
| Datensatznummer |
250117633
|
| Publikation (Nr.) |
 copernicus.org/bg-11-5539-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
The application of glycerol dialkyl glycerol tetraether (GDGT)-based
palaeoenvironmental proxies, such as the branched vs. isoprenoidal
tetratether (BIT) index, TEX86 and the MBT–CBT palaeothermometer, has
lately been expanded to lacustrine sediments. Given recent research
identifying the production of branched, bacterial GDGTs (brGDGTs) within
lakes, it is necessary to ascertain the effect of this lacustrine production
on GDGT-based proxies. This study profiles a temperate, monomictic lake (Loch
Lomond, UK), analysing labile intact polar GDGT lipids (IPLs) and resilient
core GDGT lipids (CLs) in catchment soils, small tributary rivers, lake water
and lake sediments.
Loch Lomond consists of two basins bisected by the Highland Boundary Fault,
resulting in a mesotrophic to oligotrophic gradient from south to north. The
north basin is fjord-like, while the south basin is shallow with a lowland
catchment. Besides abundant influxes of allochthonous soil- and peat-derived
(CL) brGDGTs, brGDGTs are produced in a variety of settings in Loch Lomond.
Rather than integrating a scattered soil signal, there is some evidence that
small rivers may contribute to the brGDGT pool through addition of brGDGTs
produced in situ in these streams. Three hundred days of settling particles and water
column profiles of suspended particulate matter (SPM; March and September
2011) reveal brGDGT production throughout the water column, with (IPL and
CL) brGDGT distributions varying by basin. In lake sediments, in situ brGDGT
production affects the distributions of sedimentary brGDGTs despite high
soil- and peat-derived organic matter influxes from the catchment.
MBT–CBT-derived mean annual air temperature (MAAT) estimates from soil,
river and lake sediments vary widely. A strong bias towards higher MAATs in
the south and lower MAATs in the north basin further complicates the
application of the proxy. These results emphasise that caution must be
exercised when applying the MBT–CBT palaeothermometer to individual lakes in
which the use of the proxy has not been validated and therefore the factors
affecting its application are not well understood. Despite elevated BIT
indices, (partly) due to in situ brGDGT production, reliable TEX86 lake
surface temperature (LST) estimates were obtained from SPM with BIT indices
up to 0.9. Lower north basin sediments yielded accurate LST estimates but
require further evaluation to properly constrain the application of the
TEX86 proxy. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|