The13C/12C of dissolved inorganic carbon (
- Award ID(s):
- 1652606
- NSF-PAR ID:
- 10064766
- Date Published:
- Journal Name:
- Chemical Communications
- ISSN:
- 1359-7345
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract δ 13CDIC) carries valuable information on ocean biological C‐cycling, air‐sea CO2exchange, and circulation. Paleo‐reconstructions of oceanic13C from sediment cores provide key insights into past as changes in these three drivers. As a step toward full inclusion of13C in the next generation of Earth system models, we implemented13C‐cycling in a 1° lateral resolution ocean‐ice‐biogeochemistry Geophysical Fluid Dynamics Laboratory (GFDL) model driven by Common Ocean Reference Experiment perpetual year forcing. The model improved the mean of modernδ 13CDICover coarser resolution GFDL‐model implementations, capturing the Southern Ocean decline in surfaceδ 13CDICthat propagates to the deep sea via deep water formation. Controls onδ 13CDICof the deep‐sea are quantified using both observations and model output. The biological control is estimated from the relationship between deep‐sea Pacificδ 13CDICand phosphate (PO4). Theδ 13CDIC:PO4slope from observations is revised to a value of 1.01 ± 0.02‰ (μ mol kg−1)−1, consistent with a carbon to phosphate ratio of organic matter (C:Porg) of 124 ± 10. Model output yields a lowerδ 13CDIC:PO4than observed due to too low C:Porg. The ocean circulation impacts deep modernδ 13CDICin two ways, via the relative proportion of Southern Ocean and North Atlantic deep water masses, and via the preindustrialδ 13CDICof these water mass endmembers. Theδ 13CDICof the endmembers ventilating the deep sea are shown to be highly sensitive to the wind speed dependence of air‐sea CO2gas exchange. Reducing the coefficient for air‐sea gas exchange following OMIP‐CMIP6 protocols improves significantly surfaceδ 13CDICrelative to previous gas exchange parameterizations. -
Summary Autotrophic respiration is a major driver of the global C cycle and may contribute a positive climate warming feedback through increased atmospheric concentrations of
CO 2. The extent of this feedback depends on plants' ability to acclimate respiration to maintain a constant carbon use efficiency (CUE ).We quantified respiratory partitioning of gross primary production (GPP) and
CUE of field‐grown trees in a long‐term warming experiment (+3°C). We delivered a13C–CO 2pulse to whole tree crowns and chased that pulse in the respiration of leaves, whole crowns, roots, and soil. We also measured the isotopic composition of soil microbial biomass and the respiration rates of leaves and whole crowns.We documented homeostatic respiratory acclimation of foliar and whole‐crown respiration rates; the trees adjusted to experimental warming such that leaf‐level respiration rates were not increased. Experimental warming had no detectable impact on respiratory partitioning or mean residence times. Of the13C label acquired by the trees, aboveground respiration consumed 10%, belowground respiration consumed 40%, and the remaining 50% was retained.
Experimental warming of +3°C did not alter respiratory partitioning at the scale of entire trees, suggesting that complete acclimation of respiration to warming is likely to dampen a positive climate warming feedback.
-
Abstract The ocean's biological organic carbon pump regulates the
p CO2of the atmosphere and helps maintain the oxygen distributions in the ocean. Global models of this flux are poorly verified with observations. We used upper‐ocean budgets of O2and the13C/12C of dissolved inorganic carbon (DIC) to estimate the biological pump in the subtropical gyres. These two tracers yield, within errors, similar result (~2.0 mol C·m−2·year−1) at three Northern Hemisphere subtropical locations. Values for three Southern Hemisphere subtropical regions are lower and more variable determined by the O2mass balance than by the DI13C method (−0.5 to 0.8 mol C·m−2·year−1and 0.9 to 1.3 mol C·m−2·year−1, respectively). Both methods suggest that the subtropical ocean is, on the whole, autotropic. The gas exchange residence times of O2and dissolved inorganic carbon result in different spatial and temporal averaging creating complementary tracers for biological pump model verification. -
When isotopes of carbon are fed to photosynthesizing leaves, metabolites of the Calvin–Benson cycle (CBC) are rapidly labeled initially, but then the rate of labeling slows considerably, raising questions about the integration of the CBC within leaf metabolism. We have used 2-h time courses of labeling of Camelina sativa leaf metabolites to test models of 12 C washout when the CO 2 source is rapidly switched to 13 CO 2 . Fitting exponential functions to the time course of CBC metabolites, we found evidence for three temporally distinct processes contributing to the labeling but none for metabolically inactive pools. We next modeled the data of all metabolites by 13 C isotopically nonstationary metabolic flux analysis, testing a variety of flux networks. In the model that best explains measured data, three processes determine CBC metabolite labeling. First is fixation of incoming 13 CO 2 ; second is dilution by weakly labeled carbon in cytosolic glucose reentering the CBC following oxidative pentose phosphate pathway reactions, which forms a shunt bypassing much of the CBC. Third, very weakly labeled carbon from the vacuole further dilutes the labeling. This model predicts the shunt proceeds at about 5% of the rate of net CO 2 fixation and explains the three phases of labeling. In showing the interconnection of three compartments, we have drawn a more complete picture of how carbon moves through photosynthetic metabolism in a way that integrates the CBC, cytosolic sugar pools, glucose-6-phosphate shunt, and vacuolar sugars into a single system.more » « less
-
The use of 18-crown-6 (18-c-6) in place of 2.2.2-cryptand (crypt) in rare earth amide reduction reactions involving potassium has proven to be crucial in the synthesis of Ln( ii ) complexes and isolation of their CO reduction products. The faster speed of crystallization with 18-c-6 appears to be important. Previous studies have shown that reduction of the trivalent amide complexes Ln(NR 2 ) 3 (R = SiMe 3 ) with potassium in the presence of 2.2.2-cryptand (crypt) forms the divalent [K(crypt)][Ln II (NR 2 ) 3 ] complexes for Ln = Gd, Tb, Dy, and Tm. However, for Ho and Er, the [Ln(NR 2 ) 3 ] 1− anions were only isolable with [Rb(crypt)] 1+ counter-cations and isolation of the [Y II (NR 2 ) 3 ] 1− anion was not possible under any of these conditions. We now report that by changing the potassium chelator from crypt to 18-crown-6 (18-c-6), the [Ln(NR 2 ) 3 ] 1− anions can be isolated not only for Ln = Gd, Tb, Dy, and Tm, but also for Ho, Er, and Y. Specifically, these anions are isolated as salts of a 1 : 2 potassium : crown sandwich cation, [K(18-c-6) 2 ] 1+ , i.e. [K(18-c-6) 2 ][Ln(NR 2 ) 3 ]. The [K(18-c-6) 2 ] 1+ counter-cation was superior not only in the synthesis, but it also allowed the isolation of crystallographically-characterizable products from reactions of CO with the [Ln(NR 2 ) 3 ] 1− anions that were not obtainable from the [K(crypt)] 1+ analogs. Reaction of CO with [K(18-c-6) 2 ][Ln(NR 2 ) 3 ], generated in situ , yielded crystals of the ynediolate products, {[(R 2 N) 3 Ln] 2 (μ-OCCO)} 2− , which crystallized with counter-cations possessing 2 : 3 potassium : crown ratios, i.e. {[K 2 (18-c-6) 3 ]} 2+ , for Gd, Dy, Ho. In contrast, reaction of CO with a solution of isolated [K(18-c-6) 2 ][Gd(NR 2 ) 3 ], produced crystals of an enediolate complex isolated with a counter-cation with a 2 : 2 potassium : crown ratio namely [K(18-c-6)] 2 2+ in the complex [K(18-c-6)] 2 {[(R 2 N) 2 Gd 2 (μ-OCHCHO) 2 ]}.more » « less