High-resolution carbon and oxygen isotope record in modern brachiopod Pictothyris picta collected off Okinoshima, Japan

2021 ◽  
Author(s):  
Kazuma Oikawa ◽  
Hideko Takayanagi ◽  
Kazuyoshi Endo ◽  
Masa-aki Yoshida ◽  
Yasufumi Iryu
Keyword(s):  
Isotopic Composition ◽  
Isotope Fractionation ◽  
Growth Stage ◽  
Cold Season ◽  
Strong Positive Correlation ◽  
Isotopic Equilibrium ◽  
Ambient Seawater ◽  
Kinetic Isotope ◽  
Carbon And Oxygen Isotope ◽  
Fractionation Effect

<p>Carbon (δ<sup>13</sup>C) and oxygen (δ<sup>18</sup>O) isotope composition of Rhynchonelliformea brachiopods (hereafter, called ‘brachiopods’) have been regarded as useful paleoenvironmental indicators throughout the Phanerozoic. However, recent studies have revealed that the isotopic composition in modern brachiopod shells records not only environmental changes in ambient seawater but also is influenced by biological controls such as the chemical/isotopic composition of calcifying fluids and physiological processes (e.g., growth rates, metabolism). The latter is known as biological isotope fractionation effects, such as kinetic, metabolic, and pH effects. Recently, a new calcification mechanism in brachiopod shell formation, ion transport mechanism, was proposed. In this study, we measured δ<sup>13</sup>C and δ<sup>18</sup>O values of the primary (PL) and secondary (SL) shell layers of three <em>Pictothyris picta</em> (one male and two female specimens) collected at a water depth of~61 m off Okinoshima to improve our understanding of biological isotope fractionation effects during their shell secretion. We obtained ontogenetic-series δ<sup>13</sup>C and δ<sup>18</sup>O profiles from the PL (PL-Ont) and the uppermost SL (SL-Ont) at the sampling resolution of 3 days to 8 months per sample. We obtained inner-series δ<sup>13</sup>C and δ<sup>18</sup>O profiles from the innermost SL (SL-In) as well. The variations in the δ<sup>13</sup>C and δ<sup>18</sup>O profiles of the PL-Ont showed similar trends to those of the SL-Ont. However, the PL-Ont values mostly exhibited relatively lower δ<sup>18</sup>O values than those of the SL-Ont. Cross plots between the δ<sup>13</sup>C and δ<sup>18</sup>O values of the PL-Ont indicated a strong positive correlation and were lower than those of calcite precipitated in isotopic equilibrium with ambient seawater at the fast growth stage, suggesting the significant influence of the kinetic isotope fractionation effect. The SL was precipitated in oxygen isotopic equilibrium with ambient seawater regardless of the growth stage and/or the seasonal changes in living environments. Furthermore, the PL-Ont, SL-Ont, and SL-Inshowed similar δ<sup>18</sup>O values during the cold season, indicating negligible influences of the kinetic, pH, and magnesium effects on δ<sup>18</sup>O composition. The δ<sup>13</sup>C values of the PL-Ont formed at the cold season (= micro-portion formed under the least kinetic isotope fractionation effect) were lower than those of the SL, indicating the stronger metabolic effect on the PL secretion. Our isotopic data showed that the time lag of the PL and the SL formation varies among specimens.</p>

scholarly journals Most natural-forming calcites precipitate at isotopic equilibrium

2021 ◽  
Author(s):  
Yuan jie
Keyword(s):  
Oxygen Isotope ◽  
Thermodynamic Equilibrium ◽  
Isotope Fractionation ◽  
Atomic Level ◽  
Quantum Mechanical ◽  
Isotopic Equilibrium ◽  
Oxygen Isotope Fractionation ◽  
Carbon And Oxygen Isotope ◽  
Devils Hole ◽  
Slow Growing

Abstract Based on thermodynamic equilibrium isotope fractionation theory, this letter reasonably understands the clumping 13C-18O (Δ47 ), as well as carbon and oxygen isotope fractionation in calcites with extremely slow-growing rates from Devils Hole and Laghetto Basso (Corchia Cave) at atomic level with solid physical precipitation models and quantum-mechanical backgrounds. It is found that most calcites in nature precipitate in at equilibrium.

Tellurium isotope fractionation study

1968 ◽  
Vol 46 (4) ◽  
pp. 583-591 ◽  
Author(s):  
R. M. Smithers ◽  
H. R. Krouse
Keyword(s):  
Normal Vibration ◽  
Isotope Fractionation ◽  
Sulfur Isotope ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Abundance Ratio ◽  
Isotopic Equilibrium ◽  
Kinetic Isotope ◽  
Equilibrium Exchange ◽  
Exchange Constants

"Normal vibration equations" have been solved to yield vibrational frequencies for isotopic compounds of tellurium. These frequencies were used to evaluate "partition function ratios" for 122Te- and 130Te-containing compounds. Theoretical "isotopic equilibrium exchange constants" and estimates of "kinetic isotope effects" were derived from these ratios. The results suggest that the 122Te/130Te abundance may be altered significantly in laboratory reactions and terrestrial processes.Preliminary experiments have realized kinetic isotope effects of 0.7 and 0.6% in inorganic and microbiological reductions respectively of tellurite to elemental tellurium. These results are interpreted in terms of the isotope effect in Te—O bond breakage.The maximum variation in the 130Te/122Te abundance ratio of six natural tellurides and two commercial preparations of TeO32− was found to be 0.4%.The results are compared with those found in analogous selenium and sulfur isotope investigations.

Correction of Pre-Steady-State KIEs for Isotopic Impurities and the Consequences of Kinetic Isotope Fractionation†

2008 ◽  
Vol 112 (50) ◽  
pp. 13109-13115 ◽  
Author(s):  
Sam Hay ◽  
Christopher R. Pudney ◽  
Parvinder Hothi ◽  
Nigel S. Scrutton
Keyword(s):  
Steady State ◽  
Isotope Fractionation ◽  
Kinetic Isotope

scholarly journals Investigation of post-depositional processing of nitrate in East Antarctic snow: isotopic constraints on photolytic loss, re-oxidation, and source inputs

2015 ◽  
Vol 15 (16) ◽  
pp. 9435-9453 ◽  
Author(s):  
G. Shi ◽  
A. M. Buffen ◽  
M. G. Hastings ◽  
C. Li ◽  
H. Ma ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Mass Fraction ◽  
Stratospheric Ozone ◽  
Warm Season ◽  
Cold Season ◽  
Depth Interval ◽  
Depositional Processes ◽  
Antarctic Snow ◽  
Exponential Change ◽  
The Impact

Abstract. Snowpits along a traverse from coastal East Antarctica to the summit of the ice sheet (Dome Argus) are used to investigate the post-depositional processing of nitrate (NO3−) in snow. Seven snowpits from sites with accumulation rates between 24 and 172 kg m−2 a−1 were sampled to depths of 150 to 300 cm. At sites from the continental interior (low accumulation, < 55 kg m−2 a−1), nitrate mass fraction is generally > 200 ng g−1 in surface snow and decreases quickly with depth to < 50 ng g−1. Considerably increasing values of δ15N of nitrate are also observed (16–461 ‰ vs. air N2), particularly in the top 20 cm, which is consistent with predicted fractionation constants for the photolysis of nitrate. The δ18O of nitrate (17–84 ‰ vs. VSMOW (Vienna Standard Mean Ocean Water)), on the other hand, decreases with increasing δ15N, suggestive of secondary formation of nitrate in situ (following photolysis) with a low δ18O source. Previous studies have suggested that δ15N and δ18O of nitrate at deeper snow depths should be predictable based upon an exponential change derived near the surface. At deeper depths sampled in this study, however, the relationship between nitrate mass fraction and δ18O changes, with increasing δ18O of nitrate observed between 100 and 200 cm. Predicting the impact of post-depositional loss, and therefore changes in the isotopes with depth, is highly sensitive to the depth interval over which an exponential change is assumed. In the snowpits collected closer to the coast (accumulation > 91 kg m−2 a−1), there are no obvious trends detected with depth and instead seasonality in nitrate mass fraction and isotopic composition is found. In comparison to the interior sites, the coastal pits are lower in δ15N (−15–71 ‰ vs. air N2) and higher in δ18O of nitrate (53–111 ‰ vs. VSMOW). The relationships found amongst mass fraction, δ15N, δ18O and Δ17O (Δ17O = δ17O–0.52 × δ18O) of nitrate cannot be explained by local post-depositional processes alone, and are instead interpreted in the context of a primary atmospheric signal. Consistent with other Antarctic observational and modeling studies, the isotopic results are suggestive of an important influence of stratospheric ozone chemistry on nitrate formation during the cold season and a mix of tropospheric sources and chemistry during the warm season. Overall, the findings in this study speak to the sensitivity of nitrate isotopic composition to post-depositional processing and highlight the strength of combined use of the nitrogen and oxygen isotopes for a mechanistic understanding of this processing.

scholarly journals Scale-Dependent Effects of Growth Stage and Elevational Gradient on Rice Phyllosphere Bacterial and Fungal Microbial Patterns in the Terrace Field

2022 ◽  
Vol 12 ◽  
Author(s):  
Pei Wang ◽  
Jianping Dai ◽  
Luyun Luo ◽  
Yong Liu ◽  
Decai Jin ◽  
...  
Keyword(s):  
Plant Growth ◽  
Growth Stage ◽  
Elevational Gradient ◽  
Fungal Communities ◽  
Growth Stages ◽  
Strong Positive Correlation ◽  
Elevation Gradients ◽  
Positive Correlation ◽  
Α Diversity ◽  
Phyllosphere Bacteria

The variation of phyllosphere bacterial and fungal communities along elevation gradients may provide a potential link with temperature, which corresponds to an elevation over short geographic distances. At the same time, the plant growth stage is also an important factor affecting phyllosphere microorganisms. Understanding microbiological diversity over changes in elevation and among plant growth stages is important for developing crop growth ecological theories. Thus, we investigated variations in the composition of the rice phyllosphere bacterial and fungal communities at five sites along an elevation gradient from 580 to 980 m above sea level (asl) in the Ziquejie Mountain at the seedling, heading, and mature stages, using high-throughput Illumina sequencing methods. The results revealed that the dominant bacterial phyla were Proteobacteria, Actinobacteria, and Bacteroidetes, and the dominant fungal phyla were Ascomycota and Basidiomycota, which varied significantly at different elevation sites and growth stages. Elevation had a greater effect on the α diversity of phyllosphere bacteria than on that phyllosphere fungi. Meanwhile, the growth stage had a great effect on the α diversity of both phyllosphere bacteria and fungi. Our results also showed that the composition of bacterial and fungal communities varied significantly along elevation within the different growth stages, in terms of both changes in the relative abundance of species, and that the variations in bacterial and fungal composition were well correlated with variations in the average elevation. A total of 18 bacterial and 24 fungal genera were significantly correlated with elevational gradient, displaying large differences at the various growth stages. Soluble protein (SP) shared a strong positive correlation with bacterial and fungal communities (p &lt; 0.05) and had a strong significant negative correlation with Serratia, Passalora, unclassified_Trichosphaeriales, and antioxidant enzymes (R &gt; 0.5, p &lt; 0.05), and significant positive correlation with the fungal genera Xylaria, Gibberella, and Penicillium (R &gt; 0.5, p &lt; 0.05). Therefore, it suggests that elevation and growth stage might alter both the diversity and abundance of phyllosphere bacterial and fungal populations.

scholarly journals Oxygen and silicon β-factors of zircon estimated from first principles

2019 ◽  
Vol 27 (4) ◽  
pp. 420-430
Author(s):  
D. P. Krylov
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Isotope Fractionation ◽  
Isotopic Equilibrium ◽  
Functional Theory ◽  
Empirical Calibration ◽  
The Density Functional Theory ◽  
Cubic Polynomials ◽  
Semi Empirical ◽  
Fractionation Factors

Zircon β-factors have been calibrated against temperature for isotopic substitutions of 18O/16O and 30Si/28Si. Calculations were performed using the density functional theory (DFT) with the “frozen phonon” approach. The deduced geometric parameters of the zircon unit cell, and the phonon frequencies calculated, agree well with the experimental data. The results are expressed by the cubic polynomials on x = 106/T(K)2: 1000lnβzrn(18O/16O) = 9.83055x – 0.19499x2 + 0.00388x3;  1000lnβzrn(30Si/28Si) = 7.89907x – 0.17978x2 + 0.00377x3. The expressions deduced can be utilized to construct geothermometers if combined with β-factors of coexisting phases. New calibrations of quartz-zircon are given. The new values of 1000lnβzrn and the estimated isotope fractionation factors between quartz and zircon (1000lnβqtz–1000lnβzrn) deviate considerably from previously used experimental, empirical, and semi-empirical calibration of the isotopic equilibrium.

Status-quo of carbonate cadmium isotope compositions as a paleo-productivity proxy

2021 ◽  
Author(s):  
Simon V. Hohl
Keyword(s):  
Isotopic Composition ◽  
Isotope Composition ◽  
Status Quo ◽  
Ambient Seawater ◽  
Isotopic Compositions ◽  
Marine Carbonates ◽  
The Status ◽  
State Changes ◽  
Underlying Processes ◽  
Isotope Systematics

&lt;p&gt;Cadmium (Cd) and isotope systematics are emerging tools for studying the biogeochemical cycling of micronutrients in the oceans, and sedimentary archives, as Cd concentrations in seawater show a nutrient-like behaviour, with surface depletion and deep water enrichments. However, the underlying processes are yet to be fully understood. The Cd concentration and isotopic composition of seawater are set by the balance of Cd inputs (and their isotopic composition) and the fractionation on removal to sedimentary sinks. The most favoured explanation is the Cd utilisation by marine phototrophic biomass, causing the surface water&amp;#8217;s dissolved Cd pool depletion creating a depth gradient of increasing Cd concentrations and lighter isotopic compositions. Under incomplete oxidative recycling, organic matter may act as an effective Cd sink and authigenic minerals may store the ambient seawater&amp;#8217;s Cd isotope composition.&lt;/p&gt;&lt;p&gt;Consequently, stable Cd isotope compositions in marine carbonates show broad variations linked to paleo-productivity and redox state changes. Additional fractionation processes govern the Cd isotopic compositions of marine sediments. Besides biological utilisation, experimental Cd partitioning into authigenic calcites or sulphides under variable redox and salinity conditions has been shown. &amp;#160;Therefore, when applying Cd isotopes in carbonates, other geochemical proxies must be evaluated very carefully to understand the involved Cd fractionation processes. This presentation aims to present the status quo of research done on authigenic and biologic carbonates and carbonate leachates in carbonatic shales to show the strengths and pitfalls of this new emerging bio-geoscience isotope proxy and its use for paleoenvironmental reconstructions on Earth and beyond.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Evaluation of two genera of benthic foraminifera for down-core paleotemperature studies in the western south atlantic

2006 ◽  
Vol 54 (1) ◽  
pp. 75-84 ◽  
Author(s):  
Karen B. Costa ◽  
Felipe A. L. Toledo ◽  
Maria A.G. Pivel ◽  
Cândido A.V. Moura ◽  
Farid Chemale Jr.
Keyword(s):  
Isotopic Composition ◽  
Water Temperature ◽  
Benthic Foraminifera ◽  
Small Difference ◽  
Oxygen Isotopic Composition ◽  
South Atlantic ◽  
Ambient Seawater ◽  
Oxygen Isotopic ◽  
Isotope Equilibrium ◽  
Equilibrium Oxygen

In this study we have compared the oxygen isotopic composition of two genera of benthic foraminifera (Uvigerina and Cibicidoides) from core-top samples with modern oxygen isotopic composition of seawater (delta18O). Based on a new relationship between delta18O and salinity for the mid-latitude western South Atlantic, we estimated the isotopic composition of equilibrium calcite (delta18Oeq) using two different equations: (1) O'Neil et al. (1969), modified by McCorkle et al. (1997) and (2) Kim & O'Neil (1997). When using (1), the small difference between delta18Oeq and delta18O of Uvigerina suggests that this genus precipitates its shell close to equilibrium with ambient seawater. The delta18O Cibicidoides data are 0.82 ‰ lower than the predicted (equilibrium) oxygen isotopic composition. Conversely, using (2) the Cibicidoides delta18O data show excellent agreement with the oxygen isotopic composition predicted from delta18O and water temperature while Uvigerina delta18O data are 0.69 ‰ higher than predicted oxygen isotope equilibrium values. Based on the evidences presented here and on the results from previous studies we suggest using the genus Cibicidoides and applying Kim & O'Neil's (1997) equation for down-core paleotemperature investigations. In the absence of enough Cibicidoides specimens we suggest using Uvigerina delta18O data and applying a correction factor of -0.69 ‰.

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