 |
| Titel |
Assessing the potential of amino acid 13C patterns as a carbon source tracer in marine sediments: effects of algal growth conditions and sedimentary diagenesis |
| VerfasserIn |
T. Larsen, L. T. Bach, R. Salvatteci, Y. V. Wang, N. Andersen, M. Ventura, M. D. McCarthy |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 16 ; Nr. 12, no. 16 (2015-08-21), S.4979-4992 |
| Datensatznummer |
250118070
|
| Publikation (Nr.) |
 copernicus.org/bg-12-4979-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Burial of organic carbon in marine sediments has a profound influence in
marine biogeochemical cycles and provides a sink for greenhouse gases such
as CO2 and CH4. However, tracing organic carbon from primary
production sources as well as its transformations in the sediment record
remains challenging. Here we examine a novel but growing tool for tracing
the biosynthetic origin of amino acid carbon skeletons, based on naturally
occurring stable carbon isotope patterns in individual amino acids (δ13CAA).
We focus on two important aspects for δ13CAA utility in sedimentary paleoarchives: first, the fidelity
of source diagnostic of algal δ13CAA patterns across
different oceanographic growth conditions, and second, the ability of
δ13CAA patterns to record the degree of subsequent
microbial amino acid synthesis after sedimentary burial. Using the marine
diatom Thalassiosira weissflogii, we tested under controlled conditions how δ13CAA
patterns respond to changing environmental conditions, including light,
salinity, temperature, and pH. Our findings show that while differing
oceanic growth conditions can change macromolecular cellular composition,
δ13CAA isotopic patterns remain largely invariant. These
results emphasize that δ13CAA patterns should accurately
record biosynthetic sources across widely disparate oceanographic
conditions. We also explored how δ13CAA patterns change as
a function of age, total nitrogen and organic carbon content after burial,
in a marine sediment core from a coastal upwelling area off Peru. Based on
the four most informative amino acids for distinguishing between diatom and
bacterial sources (i.e., isoleucine, lysine, leucine and tyrosine),
bacterially derived amino acids ranged from 10 to 15 % in the sediment layers from the
last 5000 years, and up to 35 % during the last glacial period. The
greater bacterial contributions in older sediments indicate that bacterial
activity and amino acid resynthesis progressed, approximately as a function
of sediment age, to a substantially larger degree than suggested by changes
in total organic nitrogen and carbon content. It is uncertain whether archaea may
have contributed to sedimentary δ13CAA patterns we
observe, and controlled culturing studies will be needed to investigate
whether δ13CAA patterns can differentiate bacterial from archeal
sources. Further research efforts are also needed to understand how closely
δ13CAA patterns derived from hydrolyzable amino acids
represent total sedimentary proteineincous material, and more broadly
sedimentary organic nitrogen. Overall, however, both our culturing and
sediment studies suggest that δ13CAA patterns in sediments
will represent a novel proxy for understanding both primary production
sources, and the direct bacterial role in the ultimate preservation
of sedimentary organic matter. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|