Carbon isotope fractionation in various forms of biogenic organic matter: I. Partitioning of carbon isotopes between the main polymers of higher plant biomass

2010 ◽  
Vol 48 (12) ◽  
pp. 1157-1165 ◽  
Author(s):  
L. A. Kodina
Keyword(s):  
Organic Matter ◽  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Isotope Fractionation ◽  
Plant Biomass ◽  
Higher Plant ◽  
Carbon Isotope Fractionation

An experimental study of carbon-isotope fractionation between diet, hair, and feces of mammalian herbivores

2003 ◽  
Vol 81 (5) ◽  
pp. 871-876 ◽  
Author(s):  
Matt Sponheimer ◽  
Todd Robinson ◽  
Linda Ayliffe ◽  
Ben Passey ◽  
Beverly Roeder ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Isotope Fractionation ◽  
Cynodon Dactylon ◽  
Isotope Composition ◽  
Mammalian Herbivores ◽  
Carbon Isotope Fractionation ◽  
Tropical Environments ◽  
The Mean ◽  
Lama Pacos

The carbon-isotope composition of hair and feces offers a glimpse into the diets of mammalian herbivores. It is particularly useful for determining the relative consumption of browse and graze in tropical environments, as these foods have strongly divergent carbon-isotope compositions. Fecal δ13C values reflect the last few days consumption, whereas hair provides longer term dietary information. Previous studies have shown, however, that some fractionation occurs between dietary δ13C values and those of hair and feces. Accurate dietary reconstruction requires an understanding of these fractionations, but few controlled-feeding studies have been undertaken to investigate these fractionations in any mammalian taxa, fewer still in large mammalian herbivores. Here, we present data from the first study of carbon-isotope fractionation between diet, hair, and feces in multiple herbivore taxa. All taxa were fed pure alfalfa (Medicago sativa) diets for a minimum period of 6 months, at which point recently grown hair was shaved and analyzed for carbon isotopes. The mean observed diet–hair fractionation was +3.2‰, with a range of +2.7 to +3.5‰. We also examined diet–feces fractionation for herbivores on alfalfa and bermudagrass (Cynodon dactylon) feeds. The mean diet–feces fractionation for both diets was –0.8‰, with less fractionation for alfalfa (–0.6‰) than bermudagrass (–1.0‰). Fecal carbon turnover also varies greatly between taxa. When diets were switched, horse (Equus caballus) feces reflected the new diet within 60 h, but alpaca (Lama pacos) feces did not equilibrate with the new diet for nearly 200 h. Thus, fecal carbon isotopes provide far greater dietary resolution for hindgut-fermenting horses than foregut-fermenting alpacas.

δ13C of organic matter transported from the leaves to the roots in Eucalyptus delegatensis: short-term variations and relation to respired CO2

2007 ◽  
Vol 34 (8) ◽  
pp. 692 ◽  
Author(s):  
Arthur Gessler ◽  
Claudia Keitel ◽  
Naomi Kodama ◽  
Christopher Weston ◽  
Anthony J. Winters ◽  
...  
Keyword(s):  
Organic Matter ◽  
Carbon Isotope ◽  
Isotope Fractionation ◽  
Stable Carbon Isotope ◽  
Water Soluble ◽  
Starch Accumulation ◽  
Diel Variation ◽  
Phloem Exudate ◽  
Carbon Isotope Fractionation ◽  
Eucalyptus Delegatensis

Post-photosynthetic carbon isotope fractionation might alter the isotopic signal imprinted on organic matter (OM) during primary carbon fixation by Rubisco. To characterise the influence of post-photosynthetic processes, we investigated the effect of starch storage and remobilisation on the stable carbon isotope signature (δ13C) of different carbon pools in the Eucalyptus delegatensis R. T. Baker leaf and the potential carbon isotope fractionation associated with phloem transport and respiration. Twig phloem exudate and leaf water-soluble OM showed diel variations in δ13C of up to 2.5 and 2‰, respectively, with 13C enrichment during the night and depletion during the day. Damped diel variation was also evident in bulk lipids of the leaf and in the leaf wax fraction. δ13C of nocturnal phloem exudate OM corresponded with the δ13C of carbon released from starch. There was no change in δ13C of phloem carbon along the trunk. CO2 emitted from trunks and roots was 13C enriched compared with the potential organic substrate, and depleted compared with soil-emitted CO2. The results are consistent with transitory starch accumulation and remobilisation governing the diel rhythm of δ13C in phloem-transported OM and fragmentation fractionation occurring during respiration. When using δ13C of OM or CO2 for assessing ecosystem processes or plant reactions towards environmental constraints, post-photosynthetic discrimination should be considered.

scholarly journals The Carbon-Isotope Record of the Sub-Seafloor Biosphere

Geosciences ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 507 ◽  
Author(s):  
Patrick Meister ◽  
Carolina Reyes
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Isotope Fractionation ◽  
Dissolved Inorganic Carbon ◽  
Isotopic Signature ◽  
Enzymatic Reactions ◽  
Deep Biosphere ◽  
Geological Time ◽  
Isotopic Signatures ◽  
Carbon Isotope Fractionation

Sub-seafloor microbial environments exhibit large carbon-isotope fractionation effects as a result of microbial enzymatic reactions. Isotopically light, dissolved inorganic carbon (DIC) derived from organic carbon is commonly released into the interstitial water due to microbial dissimilatory processes prevailing in the sub-surface biosphere. Much stronger carbon-isotope fractionation occurs, however, during methanogenesis, whereby methane is depleted in 13C and, by mass balance, DIC is enriched in 13C, such that isotopic distributions are predominantly influenced by microbial metabolisms involving methane. Methane metabolisms are essentially mediated through a single enzymatic pathway in both Archaea and Bacteria, the Wood–Ljungdahl (WL) pathway, but it remains unclear where in the pathway carbon-isotope fractionation occurs. While it is generally assumed that fractionation arises from kinetic effects of enzymatic reactions, it has recently been suggested that partial carbon-isotope equilibration occurs within the pathway of anaerobic methane oxidation. Equilibrium fractionation might also occur during methanogenesis, as the isotopic difference between DIC and methane is commonly on the order of 75‰, which is near the thermodynamic equilibrium. The isotopic signature in DIC and methane highly varies in marine porewaters, reflecting the distribution of different microbial metabolisms contributing to DIC. If carbon isotopes are preserved in diagenetic carbonates, they may provide a powerful biosignature for the conditions in the deep biosphere, specifically in proximity to the sulphate–methane transition zone. Large variations in isotopic signatures in diagenetic archives have been found that document dramatic changes in sub-seafloor biosphere activity over geological time scales. We present a brief overview on carbon isotopes, including microbial fractionation mechanisms, transport effects, preservation in diagenetic carbonate archives, and their implications for the past sub-seafloor biosphere and its role in the global carbon cycle. We discuss open questions and future potentials of carbon isotopes as archives to trace the deep biosphere through time.

Carbon isotope fractionation by photosynthetic aquatic microorganisms: experiments with Synechococcus PCC7942, and a simple carbon flux model

1998 ◽  
Vol 76 (6) ◽  
pp. 1109-1118 ◽  
Author(s):  
Jonathan Erez ◽  
Anne Bouevitch ◽  
Aaron Kaplan
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Isotope Fractionation ◽  
Isotopic Fractionation ◽  
Bisphosphate Carboxylase ◽  
Carbon Isotope Fractionation ◽  
Concentrating Mechanism ◽  
Aquatic Microorganisms ◽  
Synechococcus Pcc7942 ◽  
Flux Model

Stable carbon isotopes (12C and 13C) are widely used to trace biogeochemical processes in the global carbon cycle. Natural fractionation of carbon isotopes is mainly due to the discrimination of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) against 13C during photosynthesis. In marine and other aquatic microorganisms, this fractionation is lowered when the dissolved CO2 (CO2(aq)) is decreasing, but the underlying mechanisms are poorly understood. Cultured Synechococcus PCC7942 showed maximum isotopic fractionations of -33omicron (in delta 13C units) relative to the total inorganic carbon (Ci) when CO2(aq) is above 30 m M. As the culture grew, pH increased, CO2(aq) was lower than 1 m M, and the Ci concentrating mechanism was induced although the Ci was above 3 mM. The isotopic fractionation was drastically reduced to values of -1 to -3 omicron relative to Ci. A simple carbon isotope flux model suggests that during the first stages of the experiment the total uptake (F1) was roughly three- to four-fold greater than the photosynthetic net accumulation (F2). When the Ci concentrating mechanism was induced, the leakage of CO2 from the cells declined, the cells started to utilize HCO3- and the F1/F2 ratio decreased to values close to 1. Based on this model the isotopic variability of oceanic phytoplankton suggests that the F1/F2 ratio may be above 3 in high latitudes and ~1.1 in equatorial waters, where the Ci concentrating mechanism is probably induced. Attempts to reconstruct past atmospheric CO2 levels and paleoproductivity should take into account the effects of the Ci concentrating mechanism on the isotopic fractionation of aquatic primary producers.Key words: carbon concentrating mechanism, carbon isotope fractionation, CO2, photosynthesis.

scholarly journals Carbon Isotope Fractionation during the Formation of CO2 Hydrate and Equilibrium Pressures of 12CO2 and 13CO2 Hydrates

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4215
Author(s):  
Hiromi Kimura ◽  
Go Fuseya ◽  
Satoshi Takeya ◽  
Akihiro Hachikubo
Keyword(s):  
Carbon Isotope ◽  
Isotope Fractionation ◽  
Small Difference ◽  
Hydrate Formation ◽  
Formation Temperature ◽  
Carbon Isotope Fractionation ◽  
Unit Cell Size ◽  
Naturally Occurring ◽  
Three Phase ◽  
The Difference

Knowledge of carbon isotope fractionation is needed in order to discuss the formation and dissociation of naturally occurring CO2 hydrates. We investigated carbon isotope fractionation during CO2 hydrate formation and measured the three-phase equilibria of 12CO2–H2O and 13CO2–H2O systems. From a crystal structure viewpoint, the difference in the Raman spectra of hydrate-bound 12CO2 and 13CO2 was revealed, although their unit cell size was similar. The δ13C of hydrate-bound CO2 was lower than that of the residual CO2 (1.0–1.5‰) in a formation temperature ranging between 226 K and 278 K. The results show that the small difference between equilibrium pressures of ~0.01 MPa in 12CO2 and 13CO2 hydrates causes carbon isotope fractionation of ~1‰. However, the difference between equilibrium pressures in the 12CO2–H2O and 13CO2–H2O systems was smaller than the standard uncertainties of measurement; more accurate pressure measurement is required for quantitative discussion.

Sign in / Sign up

Export Citation Format

Share Document