The effect of carbonic anhydrase on the kinetics and equilibrium of the oxygen isotope exchange in the CO2–H2O system: Implications for δ18O vital effects in biogenic carbonates

Uchikawa, Joji; Zeebe, Richard E.

doi:10.1016/j.gca.2012.07.022

Cited by 108 publications

(96 citation statements)

References 76 publications

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“…Assuming that the ratio C / S is close to its equilibrium value (this assumption is actually required to derive Eq. 10), the ratio k h / k iso is only a function of temperature and pH (Uchikawa and Zeebe, 2012). In acidic soils, this ratio approaches 3 at any temperature, because there are three oxygen atoms in the CO 2 -H 2 O system and in this pH range, CO 2 is the dominant dissolved inorganic carbon species.…”

Section: Co 2 Mixing Ratio and Stable Isotope Measurementsmentioning

confidence: 98%

“…The soil CO 2 -H 2 O isotopic exchange rate k iso was further converted into a CO 2 hydration rate (k h ). Following Uchikawa and Zeebe (2012) we have…”

Section: Co 2 Mixing Ratio and Stable Isotope Measurementsmentioning

confidence: 99%

“…0.012 s −1 at 25 • C (Miller et al, 1999). However, because soil pH governs the speciation of CO 2 between the different carbonate forms, with dissolved CO 2 being predominant only in acidic environments (pH < 6), the true un-catalysed rate (k iso,uncat ) is not the same for all soils and is strongly reduced in alkaline conditions (Mills and Urey, 1940;Uchikawa and Zeebe, 2012). Thus for the same soil CA activity -or more precisely for the same soil CO 2 -water isotopic exchange rate (k iso ) -the enhancement factor should rather be defined relative to the true un-catalysed rate (k iso / k iso,uncat ) and would then be much greater in alkaline soils than in acidic ones.…”

Section: Introductionmentioning

confidence: 99%

“…We also artificially increased the CA concentration in each soil by adding solutions of bovine CA. This CA isoform was chosen because it is well characterised in terms of enzymatic activity (Uchikawa and Zeebe, 2012) and pH response (Rowlett et al, 1991) and it has been demonstrated that its activity was very stable in time even after several hours in solution (Uchikawa and Zeebe, 2012). Thus it was possible to investigate whether CA concentrations and soil pH were the only factors affecting the activity of this exogenous CA.…”

Section: Introductionmentioning

confidence: 99%

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The role of soil pH on soil carbonic anhydrase activity

et al. 2018

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Abstract. Carbonic anhydrases (CAs) are metalloenzymes present in plants and microorganisms that catalyse the interconversion of CO 2 and water to bicarbonate and protons. Because oxygen isotopes are also exchanged during this reaction, the presence of CA also modifies the contribution of soil and plant CO 18 O fluxes to the global budget of atmospheric CO 18 O. The oxygen isotope signatures (δ 18 O) of these fluxes differ as leaf water pools are usually more enriched than soil water pools, and this difference is used to partition the net CO 2 flux over land into soil respiration and plant photosynthesis. Nonetheless, the use of atmospheric CO 18 O as a tracer of land surface CO 2 fluxes requires a good knowledge of soil CA activity. Previous studies have shown that significant differences in soil CA activity are found in different biomes and seasons, but our understanding of the environmental and ecological drivers responsible for the spatial and temporal patterns observed in soil CA activity is still limited. One factor that has been overlooked so far is pH. Soil pH is known to strongly influence microbial community composition, richness and diversity in addition to governing the speciation of CO 2 between the different carbonate forms. In this study we investigated the CO 2 -H 2 O isotopic exchange rate (k iso ) in six soils with pH varying from 4.5 to 8.5. We also artificially increased the soil CA concentration to test how pH and other soil properties (texture and phosphate content) affected the relationship between k iso and CA concentration. We found that soil pH was the primary driver of k iso after CA addition and that the chemical composition (i.e. phosphate content) played only a secondary role. We also found an offset between the δ 18 O of the water pool with which CO 2 equilibrates and total soil water (i.e. water extracted by vacuum distillation) that varied with soil texture. The reasons for this offset are still unknown.

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Section: Co 2 Mixing Ratio and Stable Isotope Measurementsmentioning

confidence: 98%

“…The soil CO 2 -H 2 O isotopic exchange rate k iso was further converted into a CO 2 hydration rate (k h ). Following Uchikawa and Zeebe (2012) we have…”

Section: Co 2 Mixing Ratio and Stable Isotope Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The role of soil pH on soil carbonic anhydrase activity

et al. 2018

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“…The leaf water is the direct source of hydrogen in assimilates and the indirect source of oxygen via the atmospheric CO 2 dissolved in water (Schmidt et al, 2001(Schmidt et al, , 2003. The oxygen isotope composition of dissolved CO 2 equilibrates immediately with the leaf water signature, whereby carbonic anhydrase catalyses this process and induces a temperature-dependent kinetic 18 O fractionation (Gillon and Yakir, 2000;Uchikawa and Zeebe, 2012). The fractionation was assumed to be constant in this experiment with controlled temperature and was thus omitted by the calculation of the excess atom fraction.…”

Section: Calculationsmentioning

confidence: 99%

Multi-isotope labelling of organic matter by diffusion of 2H/18O-H2O vapour and 13C-CO2 into the leaves and its distribution within the plant

et al. 2015

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Abstract. Isotope labelling is a powerful tool to study elemental cycling within terrestrial ecosystems. Here we describe a new multi-isotope technique to label organic matter (OM).We exposed poplars (Populus deltoides × nigra) for 14 days to an atmosphere enriched in 13 CO 2 and depleted in 2 H 18 2 O. After 1 week, the water-soluble leaf OM (δ 13 C = 1346 ± 162 ‰) and the leaf water were strongly labelled (δ 18 O = −63 ± 8, δ 2 H = −156 ± 15 ‰). The leaf water isotopic composition was between the atmospheric and stem water, indicating a considerable back-diffusion of vapour into the leaves (58-69 %) in the opposite direction to the net transpiration flow. The atomic ratios of the labels recovered ( 18 O / 13 C, 2 H / 13 C) were 2-4 times higher in leaves than in the stems and roots. This could be an indication of the synthesis of more condensed compounds in roots and stems (e.g. lignin vs. cellulose) or might be the result of O and H exchange and fractionation processes during phloem transport and biosynthesis.We demonstrate that the three major OM elements (C, O, H) can be labelled and traced simultaneously within the plant. This approach could be of interdisciplinary interest in the fields of plant physiology, palaeoclimatic reconstruction or soil science.

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Calibration of stable isotope composition of Thoracosphaera heimii (dinoflagellate) calcite for reconstructing paleotemperatures in the intermediate photic zone

et al. 2014

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In this study we investigate the temperature dependence of oxygen isotope ratios preserved in calcite formed by the dinoflagellate Thoracosphaera heimii, focusing primarily on the development of a geological proxy. Geochemical analysis of the calcite shells produced by this species represents a valuable proxy for reconstructing environmental conditions in the intermediate photic zone. Calibration is based on isotopic analysis from culture experiments performed in very dilute batch conditions, as well as from near-monospecific T. heimii assemblages separated from core top sediments. Results are similar for both approaches and indicate that T. heimii shells have oxygen isotope compositions close to equilibrium values predicted for inorganic calcite precipitation. This calibration of the isotopic composition of dinoflagellate calcite indicates that monospecific assemblages of T. heimii can be used to unravel paleotemperatures in the intermediate photic zone by applying isotopic transfer functions for equilibrium calcite. In culture, however, a δ 18 O offset of À1‰ is observed at temperatures <17°C, which falls below the natural temperature range of this species. Culture analyses also reveal a relationship between temperature and carbon isotope composition of calcite. The mechanisms behind this relationship remain to be explored, but their identification may provide a better understanding of carbon isotope systematics from both biogeochemical and geological perspectives. Comparison of the oxygen isotope composition of T. heimii shells with that of shallower dwelling organisms, such as the coccolithophores, represents a valuable proxy for determining temperature gradients within the photic zone and may enable reconstruction of the evolution of the depth of the thermocline.

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The effect of carbonic anhydrase on the kinetics and equilibrium of the oxygen isotope exchange in the CO2–H2O system: Implications for δ18O vital effects in biogenic carbonates

Cited by 108 publications

References 76 publications

The role of soil pH on soil carbonic anhydrase activity

The role of soil pH on soil carbonic anhydrase activity

Multi-isotope labelling of organic matter by diffusion of <sup>2</sup>H/<sup>18</sup>O-H<sub>2</sub>O vapour and <sup>13</sup>C-CO<sub>2</sub> into the leaves and its distribution within the plant

Calibration of stable isotope composition of Thoracosphaera heimii (dinoflagellate) calcite for reconstructing paleotemperatures in the intermediate photic zone

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The effect of carbonic anhydrase on the kinetics and equilibrium of the oxygen isotope exchange in the CO2–H2O system: Implications for δ18O vital effects in biogenic carbonates

Cited by 108 publications

References 76 publications

The role of soil pH on soil carbonic anhydrase activity

The role of soil pH on soil carbonic anhydrase activity

Multi-isotope labelling of organic matter by diffusion of &lt;sup&gt;2&lt;/sup&gt;H/&lt;sup&gt;18&lt;/sup&gt;O-H&lt;sub&gt;2&lt;/sub&gt;O vapour and &lt;sup&gt;13&lt;/sup&gt;C-CO&lt;sub&gt;2&lt;/sub&gt; into the leaves and its distribution within the plant

Calibration of stable isotope composition of Thoracosphaera heimii (dinoflagellate) calcite for reconstructing paleotemperatures in the intermediate photic zone

Contact Info

Product

Resources

About

Multi-isotope labelling of organic matter by diffusion of <sup>2</sup>H/<sup>18</sup>O-H<sub>2</sub>O vapour and <sup>13</sup>C-CO<sub>2</sub> into the leaves and its distribution within the plant