scholarly journals Formation of Authigenic Low-Magnesium Calcite from Sites SS296 and GC53 of the Gulf of Mexico

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 251 ◽  
Author(s):  
Huiwen Huang ◽  
Shanggui Gong ◽  
Niu Li ◽  
Daniel Birgel ◽  
Jörn Peckmann ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sources ◽  
Pore Fluids ◽  
Pore Waters ◽  
Δ13c Values ◽  
Low Magnesium ◽  
Subsurface Environments ◽  
Wide Range ◽  
Magnesium Calcite

Authigenic low-magnesium calcite (LMC)—a mineral phase that should precipitate in calcite seas rather than today’s aragonite sea—was recently discovered at the seafloor of the Gulf of Mexico (GoM) at water depths of 65 m (site SS296) and 189 m (site GC53). This study investigates the mineralogical, petrographic, and geochemical characteristics of LMC from both sites to reveal its formation process. The δ18O values of LMC from site SS296 cluster in two groups (−0.6‰ to 1.7‰; 6.3‰ to 7.5‰) and the presence of cone-in-cone texture in the samples with lower δ18O values suggest precipitation at higher temperatures and greater depth. Low δ18O values of LMC from site GC53 ranging from −9.4‰ to −2.5‰ indicate an influence of meteoric waters during formation. LMC at both sites reveals a wide range of δ13C values (−17.4‰ to 2.6‰), indicating various carbon sources including seawater and/or organic matter. This interpretation is further supported by the δ13C values of organic carbon extracted from the LMC lithologies (δ13Corg: from −26.8‰ to −18.9‰). Relatively low Sr concentrations of LMC samples regardless of variable 87Sr/86Sr ratios, ranging from 0.707900 to 0.708498 for site GC53 and from 0.709537 to 0.710537 for site SS396, suggest the exchange of Sr between pore fluids and ambient sediments/rocks. The observed wide range of 87Sr/86Sr ratios and the enrichment of Fe and Mn in LMC is in accordance with pore fluids deriving from the dissolution of Louann salt. Overall, this study reveals that the formation of LMC at sites SS296 and GC53 was favored by the presence of low Mg/Ca ratio pore fluids resulting from salt dissolution in subsurface environments when sufficient dissolved inorganic carbon was available. These results are essential for understanding the formation of marine LMC at times of an aragonite sea, highlighting the role of formation environments—open environments close to or at the seafloor vs. confined subseafloor environments typified by pore waters with a composition largely different from that of seawater.

New constraints on the formation of hydrocarbon-derived low magnesium calcite at brine seeps in the Gulf of Mexico

2020 ◽  
Vol 398 ◽  
pp. 105572 ◽  
Author(s):  
Huiwen Huang ◽  
Xudong Wang ◽  
Shanggui Gong ◽  
Nicola Krake ◽  
Meng Jin ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Low Magnesium ◽  
Magnesium Calcite

scholarly journals Palaeozoic stromatoporoid diagenesis: a synthesis

Facies ◽  
2021 ◽  
Vol 67 (3) ◽  
Author(s):  
Stephen Kershaw ◽  
Axel Munnecke ◽  
Emilia Jarochowska ◽  
Graham Young
Keyword(s):  
Sediment Surface ◽  
Pore Waters ◽  
Middle Ordovician ◽  
Low Magnesium ◽  
Magnesium Calcite ◽  
Stage 1 ◽  
Diagenetic History ◽  
Pressure Dissolution

AbstractPalaeozoic stromatoporoids, throughout their 100-million + year history (Middle Ordovician to Late Devonian and rare Carboniferous), are better preserved than originally aragonite molluscs, but less well-preserved than low magnesium-calcite brachiopods, bryozoans, trilobites and corals. However, the original mineralogy of stromatoporoids remains unresolved, and details of their diagenesis are patchy. This study of approximately 2000 stromatoporoids and the literature recognises three diagenetic stages, applicable throughout their geological history. Timing of processes may vary in and between stages; some components are not always present. Stage 1, on or just below sediment surface, comprises the following: micrite filling of upper gallery space after death, then filling of any remaining space by non-ferroan then ferroan calcite in decreasing oxygen of pore-waters; partial lithification of associated sediment from which stromatoporoids may be exhumed and redeposited, evidence of general early lithification of middle Palaeozoic shallow-marine carbonates; microdolomite formation, with the Mg interpreted to have been derived from original high-Mg calcite (HMC) mineralogy (likely overlaps Stage 2). Stage 2, short distance below sediment surface, comprising the following: fabric-retentive recrystallisation (FRR) of stromatoporoid skeletons forming fabric-retentive irregular calcite (FRIC), mostly orientated normal to growth layers, best seen in cross-polarised light. FRIC stops at stromatoporoid margins in contact with sediment and bioclasts. FRIC geometry varies, indicating some taxonomic control. Evidence that FRIC formed early in diagenetic history includes syntaxial continuation of FRIC into some sub-stromatoporoid cavities (Type 1 cement), although others were pre-occupied by early cement fills (Type 2 cement) formed before FRR, preventing syntaxial continuation of FRIC into cavities. Likely contemporaneous with FRIC formation, stromatoporoids in argillaceous micrites drew carbonate from adjacent sediment during reorganisation of argillaceous micrite into limestone–marl rhythms that are also early diagenetic. Stage 3, largely shallow burial, comprises the following: dissolution and silicification, but these may have occurred earlier in stromatoporoid diagenetic histories (more data required); burial pressure dissolution forming stylolites.

scholarly journals Element Patterns of Primary Low-Magnesium Calcite from the Seafloor of the Gulf of Mexico

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 299
Author(s):  
Huiwen Huang ◽  
Xudong Wang ◽  
Shanggui Gong ◽  
Nicola Krake ◽  
Daniel Birgel ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Element Distribution ◽  
Element Composition ◽  
Element Geochemistry ◽  
Low Magnesium ◽  
Diagenetic Alteration ◽  
Homogenous Distribution ◽  
Magnesium Calcite ◽  
High Magnesium Calcite ◽  
Element Mapping

High-magnesium calcite (HMC) and aragonite are metastable minerals, which tend to convert into low-magnesium calcite (LMC) and dolomite. During this process, primary compositions are frequently altered, resulting in the loss of information regarding the formation environment and the nature of fluids from which the minerals precipitated. Petrological characteristics have been used to recognize primary LMC, however, neither the element distribution within primary LMC nor the effect of diagenetic alteration on element composition have been studied in detail. Here, two mostly authigenic carbonate lithologies from the northern Gulf of Mexico dominated by primary LMC were investigated to distinguish element compositions of primary LMC from LMC resulting from diagenetic alteration. Primary LMC reveals similar or lower Sr/Ca ratios than primary HMC. The lack of covariation between Sr/Ca ratios and Mg/Ca ratios in the studied primary LMCs are unlike compositions observed for LMC resulting from diagenetic alteration. The Sr/Mn ratios and Mn contents of the primary LMCs are negatively correlated, similar to secondary, diagenetic LMC. Element mapping for Sr and Mg in the primary LMC lithologies revealed no evidence of conversion from aragonite or HMC to LMC, and a homogenous distribution of Mn is in accordance with the absence of late diagenetic alteration. Our results confirm that Sr/Ca ratios, Mg/Ca ratios, and element systematics of primary LMC are indeed distinguishable from diagenetically altered carbonates, enabling the utilization of element geochemistry in recognizing primary signals in carbonate archives.

Natural C-14 provides new data for stream food-web studies: a comparison with C-13 in multiple stream habitats

2012 ◽  
Vol 63 (3) ◽  
pp. 210 ◽  
Author(s):  
Naoto F. Ishikawa ◽  
Masao Uchida ◽  
Yasuyuki Shibata ◽  
Ichiro Tayasu
Keyword(s):  
Food Web ◽  
Inorganic Carbon ◽  
Photosynthetic Activity ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sources ◽  
Δ13c Values ◽  
Web Studies ◽  
The Difference

In stream food-web analysis, the contributions of carbon from periphyton (an autochthonous source) and terrestrial litter (an allochthonous source) are estimated by isotopic difference. We hypothesised that periphyton δ13C varies among stream habitats, whereas Δ14C does not because Δ14C is corrected with δ13C, by definition. To test this hypothesis, we compared the variability of δ13C and Δ14C of periphyton and dissolved inorganic carbon (DIC) in four habitats (open v. shaded, riffle v. pool) within a limestone-based upland stream in Japan. Periphyton δ13C values (from –31.9‰ to –16.3‰) were significantly different among the habitats whereas the Δ14C values (from –379‰ to –141‰) were not. Periphyton δ13C values depended on both algal photosynthetic activity and δ13C of the DIC, whereas periphyton Δ14C depended only on DIC Δ14C. The δ13C and Δ14C values of litter were constant. Thus, the difference between the periphyton and litter δ13C values (Δδ13C) varied among habitats, but their Δ14C differences (ΔΔ14C) did not. Our results indicate that Δ14C is spatially stable among stream habitats and that Δ14C measurements can be used to precisely determine carbon sources for stream food-web analysis within individual reaches.

scholarly journals Burkholderia thailandensis E264 as a promising safe rhamnolipids’ producer towards a sustainable valorization of grape marcs and olive mill pomace

2021 ◽  
Author(s):  
Alif Chebbi ◽  
Massimiliano Tazzari ◽  
Cristiana Rizzi ◽  
Franco Hernan Gomez Tovar ◽  
Sara Villa ◽  
...  
Keyword(s):  
Energy Source ◽  
Olive Oil ◽  
Low Cost ◽  
Carbon Sources ◽  
Burkholderia Thailandensis ◽  
Rhamnolipid Production ◽  
Key Points ◽  
Wide Range ◽  
Long Chain ◽  
Olive Mill

Abstract Within the circular economy framework, our study aims to assess the rhamnolipid production from winery and olive oil residues as low-cost carbon sources by nonpathogenic strains. After evaluating various agricultural residues from those two sectors, Burkholderia thailandensis E264 was found to use the raw soluble fraction of nonfermented (white) grape marcs (NF), as the sole carbon and energy source, and simultaneously, reducing the surface tension to around 35 mN/m. Interestingly, this strain showed a rhamnolipid production up to 1070 mg/L (13.37 mg/g of NF), with a higher purity, on those grape marcs, predominately Rha-Rha C14-C14, in MSM medium. On olive oil residues, the rhamnolipid yield of using olive mill pomace (OMP) at 2% (w/v) was around 300 mg/L (15 mg/g of OMP) with a similar CMC of 500 mg/L. To the best of our knowledge, our study indicated for the first time that a nonpathogenic bacterium is able to produce long-chain rhamnolipids in MSM medium supplemented with winery residues, as sole carbon and energy source. Key points • Winery and olive oil residues are used for producing long-chain rhamnolipids (RLs). • Both higher RL yields and purity were obtained on nonfermented grape marcs as substrates. • Long-chain RLs revealed stabilities over a wide range of pH, temperatures, and salinities

scholarly journals Sporulation in solventogenic and acetogenic clostridia

2021 ◽  
Author(s):  
Mamou Diallo ◽  
Servé W. M. Kengen ◽  
Ana M. López-Contreras
Keyword(s):  
Current Knowledge ◽  
Carbon Sources ◽  
Cost Effective ◽  
Biotechnological Production ◽  
Key Points ◽  
Wide Range ◽  
Potential Applications ◽  
A Cell ◽  
Sporulation Initiation ◽  
Solventogenic Clostridia

AbstractThe Clostridium genus harbors compelling organisms for biotechnological production processes; while acetogenic clostridia can fix C1-compounds to produce acetate and ethanol, solventogenic clostridia can utilize a wide range of carbon sources to produce commercially valuable carboxylic acids, alcohols, and ketones by fermentation. Despite their potential, the conversion by these bacteria of carbohydrates or C1 compounds to alcohols is not cost-effective enough to result in economically viable processes. Engineering solventogenic clostridia by impairing sporulation is one of the investigated approaches to improve solvent productivity. Sporulation is a cell differentiation process triggered in bacteria in response to exposure to environmental stressors. The generated spores are metabolically inactive but resistant to harsh conditions (UV, chemicals, heat, oxygen). In Firmicutes, sporulation has been mainly studied in bacilli and pathogenic clostridia, and our knowledge of sporulation in solvent-producing or acetogenic clostridia is limited. Still, sporulation is an integral part of the cellular physiology of clostridia; thus, understanding the regulation of sporulation and its connection to solvent production may give clues to improve the performance of solventogenic clostridia. This review aims to provide an overview of the triggers, characteristics, and regulatory mechanism of sporulation in solventogenic clostridia. Those are further compared to the current knowledge on sporulation in the industrially relevant acetogenic clostridia. Finally, the potential applications of spores for process improvement are discussed.Key Points• The regulatory network governing sporulation initiation varies in solventogenic clostridia.• Media composition and cell density are the main triggers of sporulation.• Spores can be used to improve the fermentation process.

scholarly journals Tropical cyclones cumulatively control regional carbon fluxes in Everglades mangrove wetlands (Florida, USA)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xiaochen Zhao ◽  
Victor H. Rivera-Monroy ◽  
Luis M. Farfán ◽  
Henry Briceño ◽  
Edward Castañeda-Moya ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Functional Role ◽  
Net Primary Productivity ◽  
Dissolved Inorganic Carbon ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Neotropical Region ◽  
Limited Information ◽  
Organic C ◽  
Wide Range

AbstractMangroves are the most blue-carbon rich coastal wetlands contributing to the reduction of atmospheric CO2 through photosynthesis (sequestration) and high soil organic carbon (C) storage. Globally, mangroves are increasingly impacted by human and natural disturbances under climate warming, including pervasive pulsing tropical cyclones. However, there is limited information assessing cyclone’s functional role in regulating wetlands carbon cycling from annual to decadal scales. Here we show how cyclones with a wide range of integrated kinetic energy (IKE) impact C fluxes in the Everglades, a neotropical region with high cyclone landing frequency. Using long-term mangrove Net Primary Productivity (Litterfall, NPPL) data (2001–2018), we estimated cyclone-induced litterfall particulate organic C (litter-POC) export from mangroves to estuarine waters. Our analysis revealed that this lateral litter-POC flux (71–205 g C m−2 year−1)—currently unaccounted in global C budgets—is similar to C burial rates (69–157 g C m−2 year−1) and dissolved inorganic carbon (DIC, 61–229 g C m−2 year−1) export. We proposed a statistical model (PULITER) between IKE-based pulse index and NPPL to determine cyclone’s impact on mangrove role as C sink or source. Including the cyclone’s functional role in regulating mangrove C fluxes is critical to developing local and regional climate change mitigation plans.

The vulnerability of Arctic shelf sediments to climate change

2015 ◽  
Vol 23 (4) ◽  
pp. 461-479 ◽  
Author(s):  
Robie W. Macdonald ◽  
Zou Zou A. Kuzyk ◽  
Sophia C. Johannessen
Keyword(s):  
Organic Carbon ◽  
Carbon Sources ◽  
The Arctic ◽  
Sedimentary Environments ◽  
Carbon Supply ◽  
Shelf Sediment ◽  
Wide Range ◽  
Metabolic Conditions ◽  
Shelf Sediments ◽  
Ocean Ecosystem

The sediments of the pan-Arctic shelves contribute an important component to the Arctic Ocean ecosystem by providing a habitat for biota (benthos), a repository for organic and inorganic non-conservative substances entering or produced within the ocean, a reactor and source of transformed substances back to the water column, and a mechanism of burial. Sediments interact with ice, ocean, and the surrounding land over a wide range of space and time scales. We discuss the vulnerability of shelf sediment to changes in (i) organic carbon sources, (ii) pathways of sediment and organic carbon supply, and (iii) physical and biogeochemical alteration (diagenesis). Sedimentary environments of the shelves and basins are likely to exhibit a wide variance in their response to global change because of their wide variation in sediment sources, processes, and metabolic conditions. In particular, the Chukchi and Barents shelves are dominated by inflowing waters from oceans to the south, whereas the interior shelves are more closely tied to terrigenous sources due to river inflow and coastal erosion.

scholarly journals From Residues to Added-Value Bacterial Biopolymers as Nanomaterials for Biomedical Applications

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1492
Author(s):  
Francisco G. Blanco ◽  
Natalia Hernández ◽  
Virginia Rivero-Buceta ◽  
Beatriz Maestro ◽  
Jesús M. Sanz ◽  
...  
Keyword(s):  
Biomedical Applications ◽  
Carbon Sources ◽  
Structural Diversity ◽  
Added Value ◽  
Nanoscale Systems ◽  
Chemical Structures ◽  
Wide Range ◽  
Peptide Functionalization ◽  
Metabolic Strategies ◽  
Drug Nanocarriers

Bacterial biopolymers are naturally occurring materials comprising a wide range of molecules with diverse chemical structures that can be produced from renewable sources following the principles of the circular economy. Over the last decades, they have gained substantial interest in the biomedical field as drug nanocarriers, implantable material coatings, and tissue-regeneration scaffolds or membranes due to their inherent biocompatibility, biodegradability into nonhazardous disintegration products, and their mechanical properties, which are similar to those of human tissues. The present review focuses upon three technologically advanced bacterial biopolymers, namely, bacterial cellulose (BC), polyhydroxyalkanoates (PHA), and γ-polyglutamic acid (PGA), as models of different carbon-backbone structures (polysaccharides, polyesters, and polyamides) produced by bacteria that are suitable for biomedical applications in nanoscale systems. This selection models evidence of the wide versatility of microorganisms to generate biopolymers by diverse metabolic strategies. We highlight the suitability for applied sustainable bioprocesses for the production of BC, PHA, and PGA based on renewable carbon sources and the singularity of each process driven by bacterial machinery. The inherent properties of each polymer can be fine-tuned by means of chemical and biotechnological approaches, such as metabolic engineering and peptide functionalization, to further expand their structural diversity and their applicability as nanomaterials in biomedicine.

scholarly journals Sediment-water column fluxes of carbon, oxygen and nutrients in Bedford Basin, Nova Scotia, inferred from <sup>224</sup>Ra measurements

2013 ◽  
Vol 10 (1) ◽  
pp. 53-66 ◽  
Author(s):  
W. J. Burt ◽  
H. Thomas ◽  
K. Fennel ◽  
E. Horne
Keyword(s):  
Organic Matter ◽  
Nova Scotia ◽  
Water Column ◽  
Explicit Knowledge ◽  
Dissolved Inorganic Carbon ◽  
Chemical Constituents ◽  
Water Interface ◽  
Benthic Fluxes ◽  
Pore Waters ◽  
Overlying Water

Abstract. Exchanges between sediment pore waters and the overlying water column play a significant role in the chemical budgets of many important chemical constituents. Direct quantification of such benthic fluxes requires explicit knowledge of the sediment properties and biogeochemistry. Alternatively, changes in water-column properties near the sediment-water interface can be exploited to gain insight into the sediment biogeochemistry and benthic fluxes. Here, we apply a 1-D diffusive mixing model to near-bottom water-column profiles of 224Ra activity in order to yield vertical eddy diffusivities (KZ), based upon which we assess the diffusive exchange of dissolved inorganic carbon (DIC), nutrients and oxygen (O2), across the sediment-water interface in a coastal inlet, Bedford Basin, Nova Scotia, Canada. Numerical model results are consistent with the assumptions regarding a constant, single benthic source of 224Ra, the lack of mixing by advective processes, and a predominantly benthic source and sink of DIC and O2, respectively, with minimal water-column respiration in the deep waters of Bedford Basin. Near-bottom observations of DIC, O2 and nutrients provide flux ratios similar to Redfield values, suggesting that benthic respiration of primarily marine organic matter is the dominant driver. Furthermore, a relative deficit of nitrate in the observed flux ratios indicates that denitrification also plays a role in the oxidation of organic matter, although its occurrence was not strong enough to allow us to detect the corresponding AT fluxes out of the sediment. Finally, comparison with other carbon sources reveal the observed benthic DIC release as a significant contributor to the Bedford Basin carbon system.

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