 |
| Titel |
Molecular insights into the microbial formation of marine dissolved organic matter: recalcitrant or labile? |
| VerfasserIn |
B. P. Koch, G. Kattner, M. Witt, U. Passow |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 15 ; Nr. 11, no. 15 (2014-08-11), S.4173-4190 |
| Datensatznummer |
250117541
|
| Publikation (Nr.) |
 copernicus.org/bg-11-4173-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| The degradation of marine dissolved organic matter (DOM) is an important
control variable in the global carbon cycle. For our understanding of the
kinetics of organic matter cycling in the ocean, it is crucial to achieve a
mechanistic and molecular understanding of its transformation processes. A
long-term microbial experiment was performed to follow the production of
non-labile DOM by marine bacteria. Two different glucose concentrations and
dissolved algal exudates were used as substrates. We monitored the bacterial
abundance, concentrations of dissolved and particulate organic carbon (DOC,
POC), nutrients, amino acids and transparent exopolymer particles (TEP) for
2 years. The molecular characterization of extracted DOM was performed by
ultrahigh resolution Fourier transform ion cyclotron resonance mass
spectrometry (FT-ICR MS) after 70 days and after ∼2 years of
incubation. Although glucose quickly degraded, a non-labile DOC
background (5–9% of the initial DOC) was generated in the glucose
incubations. Only 20% of the organic carbon from the algal exudate
degraded within the 2 years of incubation. The degradation rates for the
non-labile DOC background in the different treatments varied between 1 and
11 μmol DOC L−1 year−1. Transparent exopolymer particles, which are released by
microorganisms, were produced during glucose degradation but decreased back
to half of the maximum concentration within less than 3 weeks
(degradation rate: 25 μg xanthan gum equivalents
L−1 d−1) and were below detection in all treatments after 2 years.
Additional glucose was added after 2 years to test whether labile substrate
can promote the degradation of background DOC (co-metabolism; priming
effect). A priming effect was not observed but the glucose addition led to a
slight increase of background DOC. The molecular analysis demonstrated that
DOM generated during glucose degradation differed appreciably from DOM
transformed during the degradation of the algal exudates. Our results led to
several conclusions: (i) based on our experimental setup, higher substrate
concentration resulted in a higher concentration of non-labile DOC; (ii) TEP,
generated by bacteria, degrade rapidly, thus limiting their potential
contribution to carbon sequestration; (iii) the molecular signatures of DOM
derived from algal exudates and glucose after 70 days of incubation differed
strongly from refractory DOM. After 2 years, however, the molecular patterns
of DOM in glucose incubations were more similar to deep ocean DOM whereas the
degraded exudate was still different. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|