scholarly journals The pH dependency of the boron isotopic composition of diatom opal (<i>Thalassiosira weissflogii</i>)

2020 ◽  
Vol 17 (10) ◽  
pp. 2825-2837 ◽  
Author(s):  
Hannah K. Donald ◽  
Gavin L. Foster ◽  
Nico Fröhberg ◽  
George E. A. Swann ◽  
Alex J. Poulton ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
High Latitude ◽  
Isotopic Fractionation ◽  
Carbon Dioxide Partial Pressure ◽  
Thalassiosira Weissflogii ◽  
The North ◽  
Seawater Ph ◽  
Ph Dependency ◽  
Carbonate Material ◽  
First Time

Abstract. The high-latitude oceans are key areas of carbon and heat exchange between the atmosphere and the ocean. As such, they are a focus of both modern oceanographic and palaeoclimate research. However, most palaeoclimate proxies that could provide a long-term perspective are based on calcareous organisms, such as foraminifera, that are scarce or entirely absent in deep-sea sediments south of 50∘ S in the Southern Ocean and north of 40∘ N in the North Pacific. As a result, proxies need to be developed for the opal-based organisms (e.g. diatoms) found at these high latitudes, which dominate the biogenic sediments recovered from these regions. Here we present a method for the analysis of the boron (B) content and isotopic composition (δ11B) of diatom opal. We apply it for the first time to evaluate the relationship between seawater pH, δ11B and B concentration ([B]) in the frustules of the diatom Thalassiosira weissflogii, cultured across a range of carbon dioxide partial pressure (pCO2) and pH values. In agreement with existing data, we find that the [B] of the cultured diatom frustules increases with increasing pH (Mejía et al., 2013). δ11B shows a relatively well defined negative trend with increasing pH, completely distinct from any other biomineral previously measured. This relationship not only has implications for the magnitude of the isotopic fractionation that occurs during boron incorporation into opal, but also allows us to explore the potential of the boron-based proxies for palaeo-pH and palaeo-CO2 reconstruction in high-latitude marine sediments that have, up until now, eluded study due to the lack of suitable carbonate material.

scholarly journals The pH dependency of the boron isotopic composition of diatom opal (<i>Thalassiosira weissflogii</i>)

2019 ◽  
Author(s):  
Hannah K. Donald ◽  
Gavin L. Foster ◽  
Nico Fröhberg ◽  
George E. A. Swann ◽  
Alex Poulton ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
High Latitude ◽  
Isotopic Fractionation ◽  
Thalassiosira Weissflogii ◽  
The North ◽  
Seawater Ph ◽  
Ph Dependency ◽  
Carbonate Material ◽  
First Time

Abstract. The high latitude oceans are key areas of carbon and heat exchange between the atmosphere and the ocean. As such, they are a focus of both modern oceanographic and palaeoclimate research. However, most palaeoclimate proxies that could provide a long-term perspective are based on calcareous organisms, such as foraminifera, that are scarce or entirely absent in deep-sea sediments south of 50° latitude in the Southern Ocean and north of 40° in the North Pacific. As a result, proxies need to be developed for the opal-based organisms (e.g. diatoms) that are found at these high latitudes, and which dominate the biogenic sediments that are recovered from these regions. Here we present a method for the analysis of the boron (B) content and isotopic composition (δ11B) of diatom opal. We also apply it for the first time to evaluate the relationship between seawater pH and δ11B and B concentration ([B]) in the frustules of the diatom Thalassiosira weissflogii, cultured at a range of pCO2/pH. In agreement with existing data, we find that the [B] of the cultured diatom frustules increases with increasing pH (Mejia et al., 2013). δ11B shows a relatively well-defined negative trend with increasing pH; a completely distinct relationship from any other biomineral previously measured. This relationship not only has implications for the magnitude of the isotopic fractionation that occurs during boron incorporation into opal, but also allows us to explore the potential of the boron-based proxies for palaeo-pH and palaeo-CO2 reconstruction in high latitude marine sediments that have, up until now, eluded study due to the lack of suitable carbonate material.

Mo mobility in lateritic weathering profiles overlying ultramafic rocks of the East Sulawesi Ophiolite, Indonesia

2021 ◽  
Author(s):  
Adrianus Damanik ◽  
Martin Wille ◽  
Martin Grosjean ◽  
Sri Yudawati Cahyarini ◽  
Hendrik Vogel
Keyword(s):  
Isotopic Composition ◽  
Chemical Weathering ◽  
Isotopic Fractionation ◽  
Reduced Form ◽  
Ultramafic Rocks ◽  
Early Earth ◽  
Atmospheric Input ◽  
First Time ◽  
Weathering Process ◽  
Mo Isotopes

&lt;p&gt;Molybdenum (Mo) isotopes are known as sensitive recorders for changes in redox conditions because the oxidized form of Mo (Mo VI) is more soluble, whereas its reduced form is more particle reactive. Previous studies suggest that Mo isotopic fractionation during the weathering process is controlled by atmospheric input, Mo host, and bedrock composition. However, Mo isotopic variation and processes influencing fractionation in weathering profiles overlying ultramafic bedrock, the early Earth analog, have yet to be explored. This study explores for the first time (1) Mo behavior and (2) isotopic fractionation in two representative and intensely-weathered lateritic profiles overlying ultramafic bedrock of the East Sulawesi Ophiolite, Indonesia. Mo concentrations measured on samples obtained from laterite successions studied here range between 60 - 537 ppb and are overall higher compared to bedrock values ranging between 9 - 45 ppb. The Mo isotope compositions of laterite samples vary between -0.043&amp;#8240; to -0.161&amp;#8240; &amp;#948;&lt;sup&gt;98&lt;/sup&gt;Mo&lt;sub&gt;NIST3134&lt;/sub&gt;. The overall close to mantle Mo isotopic composition of the laterite samples, their small Mo isotope variability, and the covariation between Mo and Ti concentrations suggest low mobility of Mo during chemical weathering and laterite formation. This low Mo mobility is likely a consequence of a) the low Mo concentration of the ultramafic protolith and b) adsorption of Mo to secondary Fe-Oxides during laterite formation under oxic weathering conditions.&lt;/p&gt;

Reading Technologies

2017 ◽  
Keyword(s):  
High Latitude ◽  
Cultural Narratives ◽  
Radio Communications ◽  
Physics Laboratory ◽  
The North ◽  
Canadian Broadcasting Corporation ◽  
Reliable Communications ◽  
First Time ◽  
The Relationship ◽  
Standard Techniques

This chapter examines the efforts to make the high-latitude ionogram legible, tracing the effects of that new legibility into wider, resonant views of the relationship between the North and communication failures. It first focuses on the transformations in the way the high-latitude ionogram was read. The same geophysical phenomena that disrupted Northern radio communications made high-latitude ionograms unreadable using standard techniques. Led by one of its founding members, Jack Meek, the Radio Physics Laboratory developed a set of reading regimes that would make these records readable for the first time. The second part of the chapter investigates how the connections built up through these techniques resonated far beyond the laboratory. By linking Northern geophysics and communications disruptions, the Laboratory furnished visual arguments for how defining elements of Canada’s northern-ness threatened reliable communications, feeding back into broader cultural narratives put forward by the Canadian Broadcasting Corporation and the geographer Louis-Edmond Hamelin.

How (not) to quantify hydrological changes using lacustrine carbonates? 

2021 ◽  
Author(s):  
Ola Kwiecien ◽  
Jeremy McCormack
Keyword(s):  
Isotopic Composition ◽  
Bottom Water ◽  
Isotopic Fractionation ◽  
Oxygen Isotopic Composition ◽  
Lake Van ◽  
Climate Reconstructions ◽  
Comprehensive Comparison ◽  
Oxygen Isotopic ◽  
Lacustrine Carbonates ◽  
First Time

&lt;p&gt;Lakes are sensitive to climate change and their sedimentary components play a pivotal role as environmental recorders. In the past, lacustrine carbonates have been utilized in a number of studies attempting at a quantitative reconstruction of rainfall and/or precipitation-evaporation changes based on the biogenic or bulk carbonate &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O signature. While these studies are built on sound theoretical grounds of mass balance and kinetic isotopic fractionation, the challenge often overlooked is the mineralogically mixed nature of carbonates comprising the bulk.&lt;/p&gt;&lt;p&gt;We report a case study from Lake Van, the world&amp;#8217;s largest alkaline lake. Our time series comprising ca. 140 ka documents not only changing proportions of surface water calcite and aragonite, but also diagenetic bottom-water dolomite and, for the first time in Lake Van, early diagenetic bottom-water aragonite. Importantly, in the Lake Van profile primary and early diagenetic carbonates (in particular aragonite) are concurrent rather than mutually exclusive. A comprehensive comparison of the &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O and &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C compositions of singled out water column, biogenic (ostracod valves) and diagenetic carbonates shows, that each of the fractions forms a distinctive cluster characteristic for the depth and timing of their formation. Also, the differences between &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O values of concurrent deep-water carbonate phases exceed what is expected from mineral-specific fractionation. Our data suggest that, an uncritical and unchecked application of the isotopic composition of the bulk carbonate fraction in quantitative climate reconstructions can severely compromise the results. We also advocate that, among different carbonate fractions in Lake Van, monospecific biogenic samples most faithfully reflect the oxygen isotopic composition of the lake water contemporaneous to their deposition, while the carbon composition of biogenic samples is additionally influenced by the organism microhabitat.&lt;/p&gt;

scholarly journals Stratospheric carbon isotope fractionation and tropospheric histories of CFC-11, CFC-12 and CFC-113 isotopologues

2020 ◽  
Author(s):  
Max Thomas ◽  
Johannes C. Laube ◽  
Jan Kaiser ◽  
Samuel Allin ◽  
Patricia Martinerie ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Carbon Isotope ◽  
Ozone Depletion ◽  
Isotope Composition ◽  
Stratospheric Ozone ◽  
Isotopic Fractionation ◽  
Base Case ◽  
Model Base ◽  
The Difference ◽  
First Time

Abstract. We present novel measurements of the carbon isotope composition of CFC-11 (CCl3F), CFC-12 (CCl2F2), and CFC-113 (CF2ClCFCl2), three atmospheric trace gases that are important for both stratospheric ozone depletion and global warming. These measurements were carried out on air samples collected in the stratosphere – the main sink region for these gases – and on air extracted from deep polar firn snow. We quantify, for the first time, the apparent isotopic fractionation, εapp(13C), for these gases as they are destroyed in the high- and mid-latitude stratosphere: εapp(CFC-12, high-lat) = (−20.2 ± 4.4) ‰ and εapp(CFC-113, high-lat) = (−9.4 ± 4.4) ‰, εapp(CFC-12, mid-lat) = (−30.3 ± 10.7) ‰, and εapp(CFC-113, mid-lat) = (−34.4 ± 9.8) ‰. Our CFC-11 measurements were not sufficient to calculate εapp(CFC-11) so we instead used previously reported photolytic fractionation for CFC-11 and CFC-12 to scale our εapp(CFC-12), resulting in εapp(CFC-11, high-lat) = (−7.8 ± 1.7) ‰ and εapp(CFC-11, mid-lat) = (−11.7 ± 4.2) ‰. Measurements of firn air were used to construct histories of the tropospheric isotopic composition, δT(13C), for CFC-11 (1950s to 2009), CFC-12 (1950s to 2009), and CFC-113 (1970s to 2009) – with δT(13C) increasing for each gas. We used εapp(high-lat), which were derived from more data, and a constant isotopic composition of emissions, δE(13C), to model δT(13C, CFC-11), δT(13C, CFC-12), and δT(13C, CFC-113). For CFC-11 and CFC-12, modelled δT(13C) was consistent with measured δT(13C) for the entire period covered by the measurements, suggesting no dramatic change in δE(13C, CFC-11) or δE(13C, CFC-12) has occurred since the 1950s. For CFC-113, our modelled δT(13C, CFC-113) did not agree with our measurements earlier than 1980. While this discrepancy may be indicative of a change in δE(13C, CFC-113), it is premature to assign one. Our modelling predicts increasing δT(13C, CFC-11), δT(13C, CFC-12), and δT(13C, CFC-113) into the future. We investigated the effect of recently reported new CFC-11 emissions on background δT(13C, CFC-11) by fixing model emissions after 2012, and comparing δT(13C, CFC-11) in this scenario to the model base case. The difference in δT(13C, CFC-11) between these scenarios was 1.4 ‰ in 2050. This difference is smaller than our model uncertainty envelope and would therefore require improved modelling and measurement precision, as well as better quantified isotopic source compositions, to detect.

Characterization and evolution of spearfishing in Madeira archipelago, Eastern Atlantic

2020 ◽  
Vol 33 ◽  
pp. 15
Author(s):  
Roi Martínez-Escauriaza ◽  
Claudio Vieira ◽  
Lídia Gouveia ◽  
Nuno Gouveia ◽  
Margarida Hermida
Keyword(s):  
Fish Species ◽  
Young Men ◽  
Coastal Areas ◽  
Teleost Fishes ◽  
The North ◽  
Southeast Coast ◽  
Madeira Archipelago ◽  
First Time

Data obtained from licenses of spearfishers and surveys conducted in 2004 and 2017 allowed for the analysis, for the first time, of the practice of spearfishing in the Madeira archipelago. Only a small percentage of the population practices spearfishing, mostly local young men. Most of them practice the activity with a partner throughout most of the year and along most of the island's coastal areas, although preferentially along the North and Southeast coast. Results show how, in recent years, despite the population of spearfishers decreasing, the abundance in the annual catch potentially increased, probably due to the higher investment of time in this activity. It has been observed that many fishers complement their catches with manual collecting of invertebrates. Overall, 40 teleost fishes and also 4 crustaceans and 8 molluscs were identified. The most frequently captured fish species were parrotfish and white seabream, while limpets were the most collected invertebrates in both selected periods.

Sphagnum mosses (Sphagnaceae, Bryophyta) of mires Chefandzar and Masota in North Ossetia (Caucasus)

2018 ◽  
Vol 52 (2) ◽  
pp. 455-462 ◽  
Author(s):  
G. Ya. Doroshina ◽  
I. A. Nikolajev
Keyword(s):  
Plant Communities ◽  
The Other ◽  
North Caucasus ◽  
Sphagnum Mosses ◽  
Greater Caucasus ◽  
The North ◽  
First Time ◽  
North Ossetia

Sphagnum mires on the Greater Caucasus are rare, characterized by the presence of relict plant communities of glacial age and are in a stage of degradation. The study of Sphagnum of Chefandzar and Masota mires is carried out for the first time. Seven species of Sphagnum are recorded. Their distribution and frequency within the North Caucasus are analyzed. Sphagnum contortum, S. platyphyllum, S. russowii, S. squarrosum are recorded for the first time for the study area and for the flora of North Ossetia. The other mosses found in the study area are listed.

Materials to the lichen flora of Samurskiy Ridge (high mountainous Dagestan)

2018 ◽  
Vol 52 (2) ◽  
pp. 397-406
Author(s):  
A. B. Ismailov ◽  
G. P. Urbanavichus
Keyword(s):  
North Caucasus ◽  
Lichenicolous Fungi ◽  
Greater Caucasus ◽  
Altitudinal Range ◽  
The North ◽  
New Findings ◽  
Mountainous Landscapes ◽  
First Time ◽  
Lichen Flora

The lichens and lichenicolous fungi of high mountainous landscapes of Samurskiy Ridge were studied in altitudinal range 2400–3770 m a. s. l. for the first time and 112 species are recorded. Among them 33 species, 10 genera (Arthrorhaphis, Baeomyces, Calvitimela, Epilichen, Lambiella, Psorinia, Rufoplaca, Sagedia, Sporastatia, Tremolecia) and 4 families (Anamylopsoraceae, Arthrorhaphidaceae, Baeomycetaceae, Hymeneliaceae) are new for Dagestan, six species (Buellia uberior, Carbonea atronivea, Lecanora atrosulphurea, Lecidea fuliginosa, L. swartzioidea, Rhizoplaca subdiscrepans) are reported for the first time for the Greater Caucasus and two species (Acarospora subpruinata and Rhizocarpon postumum) — for the North Caucasus. Most of the new findings were collected from 3500–3770 m a. s. l.

Hemiflagellochloris (Chlorophyceae, Chlorophyta), a new for Russian flora genus of green algae

2014 ◽  
Vol 48 ◽  
pp. 104-113
Author(s):  
A. D. Temraleeva ◽  
E. V. Mincheva ◽  
Yu. S. Bukin ◽  
M. V. Eltsov ◽  
V. A. Demkin ◽  
...  
Keyword(s):  
Green Algae ◽  
Molecular Analysis ◽  
18S Rdna ◽  
Phylogenetic Position ◽  
Rdna Gene ◽  
Algal Strain ◽  
The North ◽  
Volgograd Region ◽  
First Time ◽  
18S Rdna Gene

The genus Hemiflagellochloris Watanabe et al. was found in Russia for the first time. The algal strain was isolated from a buried solonetz in the zone of dry steppes (the north-end of Ergeni Hills, Volgograd Region). The morphology and ecology of this isolate are described. Its phylogenetic position within Chlorophyceae is determined by molecular analysis of 18S rDNA gene.

Sign in / Sign up

Export Citation Format

Share Document