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| Titel |
Seasonal lake surface water temperature trends reflected by heterocyst glycolipid-based molecular thermometers |
| VerfasserIn |
T. Bauersachs, J. Rochelmeier, L. Schwark |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 12 ; Nr. 12, no. 12 (2015-06-17), S.3741-3751 |
| Datensatznummer |
250117991
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| Publikation (Nr.) |
 copernicus.org/bg-12-3741-2015.pdf |
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| Zusammenfassung |
| It has been demonstrated that the relative distribution of heterocyst
glycolipids (HGs) in cultures of N2-fixing heterocystous cyanobacteria
is largely controlled by growth temperature, suggesting a potential use of
these components in paleoenvironmental studies. Here, we investigated the
effect of environmental parameters (e.g., surface water temperatures, oxygen
concentrations and pH) on the distribution of HGs in a natural system using
water column filtrates collected from Lake Schreventeich (Kiel, Germany)
from late July to the end of October 2013. HPLC-ESI/MS (high-performance liquid chromatography coupled to electrospray ionization–mass
spectrometry) analysis revealed a
dominance of 1-(O-hexose)-3,25-hexacosanediols (HG26 diols) and
1-(O-hexose)-3-keto-25-hexacosanol (HG26 keto-ol) in the solvent-extracted water column filtrates, which were accompanied by minor abundances
of 1-(O-hexose)-3,27-octacosanediol (HG28 diol) and
1-(O-hexose)-3-keto-27-octacosanol (HG28 keto-ol) as well as
1-(O-hexose)-3,25,27-octacosanetriol (HG28 triol) and
1-(O-hexose)-3-keto-25,27-octacosanediol (HG28 keto-diol). Fractional
abundances of alcoholic and ketonic HGs generally showed strong linear
correlations with surface water temperatures and no or only weak linear
correlations with both oxygen concentrations and pH. Changes in the
distribution of the most abundant diol and keto-ol (e.g., HG26 diol and
HG26 keto-ol) were quantitatively expressed as the HDI26
(heterocyst diol index of 26
carbon atoms) with values of this index ranging from 0.89 in mid-August
to 0.66 in mid-October. An average HDI26 value of 0.79, which
translates into a calculated surface water temperature of 15.8 ± 0.3 °C,
was obtained from surface sediments collected from Lake
Schreventeich. This temperature – and temperatures obtained from other HG
indices (e.g., HDI28 and HTI28) – is similar to the one measured
during maximum cyanobacterial productivity in early to mid-September and
suggests that HGs preserved in the sediment record of Lake Schreventeich
reflect summer surface water temperatures. As N2-fixing heterocystous
cyanobacteria are widespread in present-day freshwater and brackish
environments, we conclude that the distribution of HGs in sediments may
allow for the reconstruction of surface water temperatures of modern and
potentially ancient lacustrine settings. |
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