Benthic Fe-cycling in fjord sediments enhances the reactivity of glacially derived Fe in Arctic fjords of Svalbard

2020 ◽  
Author(s):  
Katja Laufer ◽  
Alexander Michaud ◽  
Hans Røy ◽  
Bo Barker Jørgensen
Keyword(s):  
Water Column ◽  
Time Course ◽  
Redox Cycling ◽  
Marine Phytoplankton ◽  
Glacial Retreat ◽  
Tidewater Glaciers ◽  
Glacial Runoff ◽  
Bedrock Lithology ◽  
The Impact ◽  
Fjord Sediments

<p>Glacial runoff is a significant source of Fe to high-latitude marine environments. The amount and characteristics of glacially derived Fe depends on bedrock lithology, glacial comminution as well as glacier type. Because much of the Fe that comes from glaciers is in the particulate phase or will become particulate once in contact with saline and oxic fjord water, much of the glacial Fe ends up in fjord sediments in close proximity to the glaciers. Within these sediments, the glacially derived Fe undergoes redox-cycling driven by indirect (abiotic reaction with metabolic products, such as hydrogen sulfide) and direct interactions with microorganisms. This redox-cycling has the potential to alter the characteristics of the glacially derived Fe and thereby also its fate, for example if it is buried in the sediment or exported to the water column.</p><p>We investigated the amount and reactivity of Fe(III) minerals from the meltwater plume, meltwater streams, icebergs, and sediments at stations with increasing distance from the glacier in three different fjords on the west coast of Spitsbergen, Svalbard. Two of the fjords have large tidewater- glaciers at their head and possess differing bedrock lithology (Kongsfjorden and Lilliehöökfjorden). The third fjord, Dicksonfjorden, has land-terminating glaciers with a bedrock lithology similar to the glaciers at the head of Kongsfjorden, thus providing insight into the impact of glacial retreat on benthic biogeochemical processes. Results from sequential and time-course extractions showed that Fe(III)-mineral reactivity increased with distance from the glacier fronts and decreased with sediment depth at each station in all three fjords. Fe(III)-oxide reactivity from different glacial sources (meltwater plume and iceberg material from tidewater glaciers and meltwater stream material from land-terminating glaciers) differed based on source type and Fe(III) from all glacial sources was generally less reactive compared to surficial sediments distal to the glacier front. While the general trends were the same for all three fjords, based on pore water profiles of dissolved Fe, we found a lower potential for Fe-export to the water column when only land-terminating glaciers were present. This difference highlights that glacial retreat potentially impacts the function of fjord sediments as a source of Fe to the water column. We conclude that glacial runoff supplies large quantities of Fe minerals to fjord sediments, but benthic recycling of Fe by microorganisms transforms the relatively unreactive glacially-derived Fe(III)-oxides to a more reactive form. Microbially driven recycling of reactive Fe(III)-oxides in fjord sediments may play a role in liberating Fe to the water column, predominantly at the mouth of the fjord, and might represent an unquantified source of Fe to Fe-limited marine phytoplankton.</p>

scholarly journals Complex Microbial Communities Drive Iron and Sulfur Cycling in Arctic Fjord Sediments

2019 ◽  
Vol 85 (14) ◽  
Author(s):  
J. Buongiorno ◽  
L. C. Herbert ◽  
L. M. Wehrmann ◽  
A. B. Michaud ◽  
K. Laufer ◽  
...  
Keyword(s):  
Organic Matter ◽  
Primary Production ◽  
Sulfate Reduction ◽  
The Arctic ◽  
Sulfur Cycling ◽  
Glacial Retreat ◽  
Sulfate Reducing ◽  
Glacial Runoff ◽  
Sulfate Reduction Rates ◽  
Fjord Sediments

ABSTRACTGlacial retreat is changing biogeochemical cycling in the Arctic, where glacial runoff contributes iron for oceanic shelf primary production. We hypothesize that in Svalbard fjords, microbes catalyze intense iron and sulfur cycling in low-organic-matter sediments. This is because low organic matter limits sulfide generation, allowing iron mobility to the water column instead of precipitation as iron monosulfides. In this study, we tested this with high-depth-resolution 16S rRNA gene libraries in the upper 20 cm at two sites in Van Keulenfjorden, Svalbard. At the site closer to the glaciers, iron-reducingDesulfuromonadales, iron-oxidizingGallionellaandMariprofundus, and sulfur-oxidizingThiotrichalesandEpsilonproteobacteriawere abundant above a 12-cm depth. Below this depth, the relative abundances of sequences for sulfate-reducingDesulfobacteraceaeandDesulfobulbaceaeincreased. At the outer station, the switch from iron-cycling clades to sulfate reducers occurred at shallower depths (∼5 cm), corresponding to higher sulfate reduction rates. Relatively labile organic matter (shown by δ13C and C/N ratios) was more abundant at this outer site, and ordination analysis suggested that this affected microbial community structure in surface sediments. Network analysis revealed more correlations between predicted iron- and sulfur-cycling taxa and with uncultured clades proximal to the glacier. Together, these results suggest that complex microbial communities catalyze redox cycling of iron and sulfur, especially closer to the glacier, where sulfate reduction is limited due to low availability of organic matter. Diminished sulfate reduction in upper sediments enables iron to flux into the overlying water, where it may be transported to the shelf.IMPORTANCEGlacial runoff is a key source of iron for primary production in the Arctic. In the fjords of the Svalbard archipelago, glacial retreat is predicted to stimulate phytoplankton blooms that were previously restricted to outer margins. Decreased sediment delivery and enhanced primary production have been hypothesized to alter sediment biogeochemistry, wherein any free reduced iron that could potentially be delivered to the shelf will instead become buried with sulfide generated through microbial sulfate reduction. We support this hypothesis with sequencing data that showed increases in the relative abundance of sulfate reducing taxa and sulfate reduction rates with increasing distance from the glaciers in Van Keulenfjorden, Svalbard. Community structure was driven by organic geochemistry, suggesting that enhanced input of organic material will stimulate sulfate reduction in interior fjord sediments as glaciers continue to recede.

scholarly journals Computational Evaluation of Shock Wave Interaction with a Cylindrical Water Column

2021 ◽  
Vol 11 (11) ◽  
pp. 4934
Author(s):  
Viola Rossano ◽  
Giuliano De Stefano
Keyword(s):  
Shock Wave ◽  
Water Column ◽  
Wave Interaction ◽  
Navier Stokes ◽  
Plane Shock ◽  
Governing Equations ◽  
Computational Evaluation ◽  
Air Water Interface ◽  
The Mean ◽  
The Impact

Computational fluid dynamics was employed to predict the early stages of the aerodynamic breakup of a cylindrical water column, due to the impact of a traveling plane shock wave. The unsteady Reynolds-averaged Navier–Stokes approach was used to simulate the mean turbulent flow in a virtual shock tube device. The compressible flow governing equations were solved by means of a finite volume-based numerical method, where the volume of fluid technique was employed to track the air–water interface on the fixed numerical mesh. The present computational modeling approach for industrial gas dynamics applications was verified by making a comparison with reference experimental and numerical results for the same flow configuration. The engineering analysis of the shock–column interaction was performed in the shear-stripping regime, where an acceptably accurate prediction of the interface deformation was achieved. Both column flattening and sheet shearing at the column equator were correctly reproduced, along with the water body drift.

Decline of contractility during ischemia-reperfusion injury: actin glutathionylation and its effect on allosteric interaction with tropomyosin

2006 ◽  
Vol 290 (3) ◽  
pp. C719-C727 ◽  
Author(s):  
Frank C. Chen ◽  
Ozgur Ogut
Keyword(s):  
Reperfusion Injury ◽  
Posttranslational Modifications ◽  
Actin Polymerization ◽  
Time Course ◽  
Troponin I ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
High Concentration ◽  
Cross Sectional ◽  
The Impact

The severity and duration of ischemia-reperfusion injury is hypothesized to play an important role in the ability of the heart subsequently to recover contractility. Permeabilized trabeculae were prepared from a rat model of ischemia-reperfusion injury to examine the impact on force generation. Compared with the control perfused condition, the maximum force (Fmax) per cross-sectional area and the rate of tension redevelopment of Ca2+-activated trabeculae fell by 71% and 44%, respectively, during ischemia despite the availability of a high concentration of ATP. The reduction in Fmax with ischemia was accompanied by a decline in fiber stiffness, implying a drop in the absolute number of attached cross bridges. However, the declines during ischemia were largely recovered after reperfusion, leading to the hypothesis that intrinsic, reversible posttranslational modifications to proteins of the contractile filaments occur during ischemia-reperfusion injury. Examination of thin-filament proteins from ischemic or ischemia-reperfused hearts did not reveal proteolysis of troponin I or T. However, actin was found to be glutathionylated with ischemia. Light-scattering experiments demonstrated that glutathionylated G-actin did not polymerize as efficiently as native G-actin. Although tropomyosin accelerated the time course of native and glutathionylated G-actin polymerization, the polymerization of glutathionylated G-actin still lagged native G-actin at all concentrations of tropomyosin tested. Furthermore, cosedimentation experiments demonstrated that tropomyosin bound glutathionylated F-actin with significantly reduced cooperativity. Therefore, glutathionylated actin may be a novel contributor to the diverse set of posttranslational modifications that define the function of the contractile filaments during ischemia-reperfusion injury.

Biogeochemical and ecological features of sinking particulate matter in the deep Ionian Sea (E. Mediterranean) during a 10-year time series study: impacts of atmospheric and oceanographic variabilities on carbon production and sequestration

2021 ◽  
Author(s):  
Alexandra Gogou ◽  
Constantine Parinos ◽  
Spyros Stavrakakis ◽  
Emmanouil Proestakis ◽  
Maria Kanakidou ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Organic Carbon ◽  
Carbon Cycle ◽  
Atmospheric Deposition ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Nutrient Dynamics ◽  
Ionian Sea ◽  
Ecological Features ◽  
The Impact

<p>Biotic and abiotic processes that form, alter, transport, and remineralize particulate organic carbon, silicon, calcium carbonate, and other minor and trace chemical species in the water column are central to the ocean’s ecological and biogeochemical functioning and of fundamental importance to the ocean carbon cycle. Sinking particulate matter is the major vehicle for exporting carbon from the sea surface to the deep sea. During its transit towards the sea floor, most particulate organic carbon (POC) is returned to inorganic form and redistributed in the water column. This redistribution determines the surface concentration of dissolved CO<sub>2</sub>, and hence the rate at which the ocean can absorb CO<sub>2</sub> from the atmosphere. The ability to predict quantitatively the depth profile of remineralization is therefore critical to deciphering the response of the global carbon cycle to natural and human-induced changes.</p><p>Aiming to investigate the significant biogeochemical and ecological features and provide new insights on the sources and cycles of sinking particulate matter, a mooring line of five sediment traps was deployed from 2006 to 2015 (with some gap periods) at 5 successive water column depths (700, 1200, 2000, 3200 and 4300 m) in the SE Ionian Sea, northeastern Mediterranean (‘NESTOR’ site). We have examined the long-term records of downward fluxes for Corg, N<sub>tot</sub>, δ<sup>13</sup>Corg and δ<sup>15</sup>N<sub>tot</sub>, along with the associated ballast minerals (opal, lithogenics and CaCO<sub>3</sub>), lipid biomarkers, Chl-a and PP rates, phytoplankton composition, nutrient dynamics and atmospheric deposition.  </p><p>The satellite-derived seasonal and interannual variability of phytoplankton metrics (biomass and phenology) and atmospheric deposition (meteorology and air masses origin) was examined for the period of the sediment trap experiment. Regarding the atmospheric deposition, synergistic opportunities using Earth Observation satellite lidar and radiometer systems are proposed (e.g. Cloud‐Aerosol Lidar with Orthogonal Polarization - CALIOP, Moderate Resolution Imaging Spectroradiometer - MODIS), aiming towards a four‐dimensional exploitation of atmospheric aerosol loading (e.g. Dust Optical Depth) in the study area.</p><p>Our main goals are to: i) develop a comprehensive knowledge of carbon fluxes and associated mineral ballast fluxes from the epipelagic to the mesopelagic and bathypelagic layers, ii) elucidate the mechanisms governing marine productivity and carbon export and sequestration to depth and iii) shed light on the impact of atmospheric forcing and deposition in respect to regional and large scale circulation patterns and climate variability and the prevailing oceanographic processes (internal variability).</p><p>Acknowledgments</p><p>We acknowledge support of this work by the Action ‘National Network on Climate Change and its Impacts – <strong>CLIMPACT</strong>’, funded by the Public Investment Program of Greece (GSRT, Ministry of Development and Investments).</p>

Abstract 160: Pim-1 Preserves Cardiac Stem Cell Proliferation with Age

2012 ◽  
Vol 111 (suppl_1) ◽  
Author(s):  
Michael McGregor ◽  
Shabana Din ◽  
Natalie Gude ◽  
Mark A Sussman
Keyword(s):  
Cell Proliferation ◽  
Stem Cell ◽  
Time Course ◽  
Protein A ◽  
Cell Types ◽  
Tissue Homeostasis ◽  
Dominant Negative ◽  
Repair Capacity ◽  
Tissue Samples ◽  
The Impact

Rationale Cardiac stem cells (CSC) regulate cardiomyogenesis and support regenerative processes in the heart, but aging adversely affects stem cell repair capacity. Aging is a primary cause of impaired cardiac function characterized by accumulation of senescent cells. CSC senescence is associated with permanent growth arrest that decreases survival signaling and cellular replacement, inevitably diminishing the capacity of the heart to maintain tissue homeostasis. Therefore, promoting CSC growth may improve cardiac performance with age. Pim-1 kinase exhibits protective and proliferative effects in the myocardium but the role of Pim-1 in cardiac aging has not been thoroughly studied. Objective Demonstrate that Pim-1 promotes stem cell growth in the aged myocardium correlating with increased expression of centromere protein A (CENP-A), a kinetochore-associated protein known to support cell proliferation in numerous species and cell types. Methods & Results CENP-A expression levels were evaluated from murine myocardial tissue samples ranging in age from 11 days post coitum to 4 months of age with analysis by immunoblot as well as quantitative PCR. CENP-A expression was colocalized with c-kit as a marker of CSC by immunohistochemical labeling, revealing a decline in CENP-A expression over the time course of postnatal myocardial maturation. The impact of Pim-1 upon CENP-A level was assessed by comparative analysis of non-transgenic mice versus genetically modified transgenic mouse lines expressing either Pim-1 (wild type) or a dominant negative functionally dead Pim-1 mutant. Pim-1 overexpression increases persistence of CENP-A in CSCs with age, as well as the prevalence of cycling CSCs as marked by phosph-H3 expression, while the functionally dead mutant accelerates CENP-A diminution and decreases CSC proliferation. Conclusion CENP-A decline in c-kit positive cells with age provides intriguing evidence of a potential mechanism for the diminished capacity of CSCs to maintain tissue homeostasis. Pim-1 mitigates CENP-A diminution, demonstrating the promising potential of Pim-1 to promote cardiac growth and repair with age.

scholarly journals The mass impacts on chemosynthetic primary producers: potential implications on anammox communities and their consequences

2018 ◽  
Vol 18 (05) ◽  
pp. 440-444
Author(s):  
Noel Pérez ◽  
Jorge Luis Velazco-Vargas ◽  
Osmel Martin ◽  
Rolando Cardenas ◽  
Jesús Martínez-Frías
Keyword(s):  
Water Column ◽  
Deposition Rate ◽  
Extreme Case ◽  
Chemical Compounds ◽  
Global Scale ◽  
Biogeochemical Cycle ◽  
Potential Influence ◽  
Asteroid Impact ◽  
Global Cooling ◽  
The Impact

AbstractThe potential of a mass asteroid impact on Earth to disturb the chemosynthetic communities at global scale is discussed. Special emphasis is made on the potential influence on anammox communities and their implications in the nitrogen biogeochemical cycle. According to our preliminary estimates, anammox communities could be seriously affected as a consequence of global cooling and the large process of acidification usually associated with the occurrence of this kind of event. The scale of affectations could vary in a scenario like the Chicxulub as a function of the amount of soot, depth of the water column and the deposition rate for sulphates assumed in each case. The most severe affectations take place where the amount of soot and sulphates produced during the event is higher and the scale of time of settlements for sulphates is short, of the order of 10 h. In this extreme case, the activity of anammox is considerably reduced, a condition that may persist for several years after the impact. Furthermore, the impact of high levels of other chemical compounds like sulphates and nitrates associated with the occurrence of this kind of event are also discussed.

scholarly journals Lack of Obvious Influence of PLLA Nanofibers on the Gene Expression of BMP-2 and VEGF during Growth and Differentiation of Human Mesenchymal Stem Cells

2009 ◽  
Vol 9 ◽  
pp. 313-319 ◽  
Author(s):  
Markus D. Schofer ◽  
S. Fuchs-Winkelmann ◽  
C. Wack ◽  
M. Rudisile ◽  
R. Dersch ◽  
...  
Keyword(s):  
Gene Expression ◽  
Growth Factor ◽  
Time Course ◽  
Negative Impact ◽  
Fracture Repair ◽  
Bone Morphogenetic Protein 2 ◽  
Vegf Gene ◽  
Down Regulation ◽  
Artificial Graft ◽  
The Impact

Growth factors like bone morphogenetic protein 2 (BMP-2) and vascular endothelial growth factor (VEGF) play an important role in bone remodeling and fracture repair. Therefore, with respect to tissue engineering, an artificial graft should have no negative impact on the expression of these factors. In this context, the aim of this study was to analyze the impact of poly(L-lactic acid) (PLLA) nanofibers on VEGF and BMP-2 gene expression during the time course of human mesenchymal stem cell (hMSC) differentiation towards osteoblasts. PLLA matrices were seeded with hMSCs and cultivated over a period of 22 days under growth and osteoinductive conditions, and analyzed during the course of culture, with respect to gene expression of VEGF and BMP-2. Furthermore, BMP-2–enwoven PLLA nanofibers were used in order to elucidate whether initial down-regulation of growth factor expression could be compensated. Although there was a great interpatient variability with respect to the expression of VEGF and BMP-2, PLLA nanofibers tend to result in a down-regulation in BMP-2 expression during the early phase of cultivation. This effect was diminished in the case of VEGF gene expression. The initial down-regulation was overcome when BMP-2 was directly incorporated into the PLLA nanofibers by electrospinning. Furthermore, the incorporation of BMP-2 into the PLLA nanofibers resulted in an increase in VEGF gene expression. Summarized, the results indicate that the PLLA nanofibers have little effect on growth factor production. An enhancement in gene expression of BMP-2 and VEGF can be achieved by an incorporation of BMP-2 into the PLLA nanofibers.

scholarly journals Straight to Low-Sinuosity Drainage Systems in a Variscan-Type Orogen—Constraints from Tectonics, Lithology and Climate

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 933
Author(s):  
Harald G. Dill ◽  
Andrei Buzatu ◽  
Sorin-Ionut Balaban
Keyword(s):  
Chemical Weathering ◽  
Current Model ◽  
Drainage System ◽  
Numerical Data ◽  
Structural Features ◽  
Acute Angle ◽  
Drainage Systems ◽  
Starting Point ◽  
Bedrock Lithology ◽  
The Impact

A holistic-modular approach has been taken to study the evolution of three straight to low-sinuosity drainage systems (=SSS) in an uplifted basement block of the Central European Variscides. The development of the SSS is described by means of a quadripartite model. (1) The geological framework of the SSS: Forming the lithological and structural features in the bedrock as a result of different temperature, pressure and dynamic-metamorphic processes. (2) Prestage of SSS: Forming the paleo-landscape with a stable fluvial regime as a starting point for the SSS. (3) Proto-SSS: Transition into the metastable fluvial regime of the SSS. (4) Modern SSS: Operation of the metastable fluvial regime Tectonics plays a dual role. Late Paleozoic fold tectonic creates the basis for the studied SSS and has a guiding effect on the development of morphotectonic units during the Neogene and Quaternary. Late Cenozoic fault tectonics triggered the SSS to incise into the Paleozoic basement. The change in the bedrock lithology has an impact on the fluvial and colluvial sediments as well as their landforms. The latter reflects a conspicuous modification: straight drainage system ⇒ higher sinuosity and paired terraces ⇒ hillwash plains. Climate change has an indirect effect controlling via the bedrock the intensity of mechanical and chemical weathering. The impact on the development of the SSS can be assessed as follows: Tectonics >> climate ≅ bedrock lithology. The three parameters cause a facies zonation: (1) wide-and-shallow valley (Miocene), (2) wide-angle V-shaped valley (Plio-Pleistocene), (3) acute-angle V-shaped valley (Pleistocene), (4) V-shaped to U-shaped valleys (Pleistocene-Holocene). Numerical data relevant for the hydrographic studies of the SSS are determined in each reference area: (1) Quantification of fluvial and colluvial deposits along the drainage system, (2) slope angles, (3) degree of sinuosity as a function of river facies, (4) grain size distribution, (5) grain morphological categorization, (6) grain orientation (“situmetry”), (7) channel density, (8) channel/floodplain ratios. Thermodynamic computations (Eh, pH, concentration of solubles) are made to constrain the paleoclimatic regime during formation of the SSS. The current model of the SSS is restricted in its application to the basement of the Variscan-Type orogens, to an intermediate crustal maturity state.

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