Publication Details |
| Category | Text Publication |
| Reference Category | Journals |
| DOI | 10.1016/j.gca.2024.12.003 |
Licence  |
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| Title (Primary) | Invariable selection of compounds from organic matter by stream microbes |
| Author | Tittel, J.; Lüderitz, V.; Radke, S.; Rosenlöcher, Y.; Lechtenfeld, O.J.
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| Source Titel | Geochimica et Cosmochimica Acta |
| Year | 2025 |
| Department | SEEFO; EAC |
| Volume | 392 |
| Page From | 107 |
| Page To | 118 |
| Language | englisch |
| Topic | T5 Future Landscapes |
| Supplements | https://ars.els-cdn.com/content/image/1-s2.0-S0016703724006318-mmc1.pdf |
| Keywords | DOC; DOM; Decomposition; Radiocarbon; 14C; FT-ICR MS; Microbes |
| Abstract | Organic carbon (OC) in rivers is one of the most rapidly recycled carbon
pools. A significant proportion of OC is remineralized and contributes
to the globally relevant CO2 emissions of river networks.
However, there is no consensus on the mechanisms that determine which
compounds are remineralized. Previous studies found that OC older than
the mean age of the source was decomposed by aquatic microorganisms.
Here, we study the radiocarbon (Δ14C) age of dissolved OC
(DOC) that is decomposed in laboratory experiments across a range of
stream bulk DOC ages. Stream DOC was collected from small forested
catchments under summer dry flow, average flow and storm flow
conditions. The decomposed DOC was neither consistently older nor
younger than the original stream DOC. The Δ14C of respiratory CO2 increased with the Δ14C of stream DOC (P = 0.006, N = 16). However, the slope of the regression was small (0.20 ± 0.06) and the dependence was weak (R2 = 0.43).
Moreover, the age range of respired DOC (modern to 950 years BP) was
considerably narrower than the age range of stream DOC (modern to
3880 years BP). In further experiments, we used leachates of catchment
soil from 0-8 cm and 8–20 cm depth and a 1:1 mixture of the two depths
as initial DOC. Again, the increase in Δ14C-CO2 as a function of Δ14C-DOC was significant (R2 = 0.74, P = 0.028, N
= 6), but the slope was small (0.13 ± 0.04) and the age range of
respired DOC was narrow (modern to 280 years BP) compared to initial
leachate DOC (600 to 3400 years BP). Fourier-transform ion cyclotron
resonance mass spectrometry showed that the dissolved organic matter
(DOM) starting material from the deeper soil layer was characterized by
smaller, more reduced (i.e. aliphatic) molecules as compared to the DOM
from the shallower soil layer. However, similar (small, unsaturated,
oxygen-rich) CHO molecules were consumed regardless of DOM source. The
narrow age ranges of respired DOC suggest that intrinsic chemical
quality sets the limits for which compounds can be utilized under given
geochemical conditions. However, strategies of microorganisms to
optimize growth (optimal foraging) may modulate their specific substrate
choice, as indicated by the dependence of the age of respired OC on the
age composition of the original DOC. Analysis of published decomposition experiments showed that in 60% of measurements the decomposed OC was older than the original river or lake OC, excluding studies with peat-derived OC or OC affected by permafrost thaw. However, due to the freshwater reservoir effect (photosynthetic assimilation of 14C-old inorganic carbon), existing data provide no consistent evidence that either younger or older OC is preferentially decomposed. |
| Persistent UFZ Identifier | https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=30074 |
| Tittel, J., Lüderitz, V., Radke, S., Rosenlöcher, Y., Lechtenfeld, O.J. (2025): Invariable selection of compounds from organic matter by stream microbes Geochim. Cosmochim. Acta 392 , 107 - 118 10.1016/j.gca.2024.12.003 |
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