Abstract
Biodegradation process of dissolved organic matter (DOM) could be affected by its concentration and quality. Two biodegradation experiments were conducted in two contrasting seasons in two ...oligotrophic and one ultraoligotrophic temperate lakes, which comprise a natural gradient of dissolved organic carbon (DOC) concentration and quality (including lakes of < 83.33 μM). We examined associations between biodegradation and bacterial cytometric descriptors (i.e. abundance, DNA relative content, etc.) and with different DOM characteristics. The biolabile DOC (BDOC) was higher in shallow oligotrophic lakes, which displayed higher DOC concentration than the deep ultraoligotrophic one. The BDOC was mainly relatable not only to DOC concentration but also with DOM quality fluorescent terrestrial-humic component normalized by DOC (C2:DOC), lignin content (a*350) and biological index. We found a positive association between biodegradation process and high nucleic acid–content bacterial group. The bacterioplankton cytometric features were shaped by DOM concentration and quality along the biodegradation process. We concluded that in oligotrophic lakes, DOC concentration was the main driver of BDOC, whereas in ultraoligotrophic lakes, DOM quality played a more central role. This study contributes to better understand the biodegradation process in pristine low-DOC lakes with natural variation in allochthonous DOM inputs and with implications in the biogeochemical cycles.
Undaria pinnatifida is a brown algae native to Asia that has settled in various regions worldwide, periodically contributing with large quantities of C and nutrients during its annual cycle. In this ...work, we analyzed a coastal site in Patagonia (Argentina) that has been colonized for three decades by U. pinnatifida, focusing on associated microbial communities in three different compartments. An important influence of algae was observed in seawater, especially in the bottom of the algal forest during the austral summer (January) at the moment of greater biomass release. This was evidenced by changes in DOC concentration and its quality indicators (higher Freshness and lower Humification index) and higher DIC. Although maximum values of NH4 and PO4 were observed in January, bottom water samples had lower concentrations than surface water, suggesting nutrient consumption by bacteria during algal DOM release. Concomitantly, bacterial abundance peaked, reaching 4.68 ± 1.33 × 105 cells mL −1 (January), showing also higher capability of degrading alginate, a major component of brown algae cell walls. Microbial community structure was influenced by sampling date, season, sampling zone (surface or bottom), and environmental factors (temperature, salinity, pH, dissolved oxygen, nutrients). Samples of epiphytic biofilms showed a distinct community structure compared to seawater, lower diversity, and remarkably high alginolytic capability, suggesting adaptation to degrade algal biomass. A high microdiversity of populations of the genus Leucothrix (Gammaproteobacteria, Thiotrichales) that accounted for a large fraction of epiphytic communities was observed, and changed over time. Epiphytic assemblages shared more taxa with bottom than with surface seawater assemblages, indicating a certain level of exchange between communities in the forest surroundings. This work provides insight into the impact of U. pinnatifida decay on seawater quality, and the role of microbial communities on adapting to massive biomass inputs through rapid DOM turnover.
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•Invasive kelp U. pinnatifida reshapes coastal environments in Patagonia.•Kelp senescence enhances DOC, POC and nutrients, impacting associated communities.•Kelp forest holds distinct epiphytic and free-living microbial assemblages.•Epiphytic and bottom seawater microbes have a key role in algal-derived DOM breakdown.•Specialized populations in epiphytic biofilms show the highest alginate-degrading potential.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Optical spectroscopy, FT-ICR MS and microbial sequencing were employed to analyze DOM.•Sediment DOM, DON and DOS showed reduced molecular diversity but enhanced reactivity ...seaward.•Contribution of terrestrial OM to sediment DOM transformation decreased seaward.•Microbial consumption of labile DON and DOS components alters their properties.•Anthropogenic inputs can enhance DOM bio-reactivity by increasing DON and DOS fractions.
Dissolved organic matter (DOM) constitutes the most active fraction in global carbon pools, with estuarine sediments serving as significant repositories, where DOM is susceptible to dynamic transformations. Anthropogenic nitrogen (N) and sulfur (S) inputs further complicate DOM by creating N-bearing DOM (DON) and S-bearing DOM (DOS). This study delves into the spatial gradients and transformation mechanisms of DOM, DON, and DOS in Pearl River Estuary (PRE) sediments, China, using combined techniques of UV–visible spectroscopy, Excitation–emission matrix (EEM) fluorescence spectroscopy, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and microbial high-throughput sequencing. Results uncovered a distinct spatial gradient in DOM concentration, aromaticity (SUVA254), hydrophobicity (SUVA260), the content of substituent groups including carboxyl, carbonyl, hydroxyl and ester groups (A253/A203) of chromophoric DOM (CDOM), and the abundances of tyrosine/tryptophan-like protein and humic-like substances in fluorophoric DOM (FDOM). These all decreased from upper to lower PRE, accompanied by a decrease in O3S and O5S components, indicating seaward reduction in the contribution of terrestrial OM, especially anthropogenic inputs. Additionally, sediments exhibited a reduction in molecular diversity (number of formulas) of DOM, DON, and DOS from upper to lower PRE, with molecules tending towards a lower nominal oxidation state of carbon (NOSC) and higher bio-reactivity (MLBL), molecular weight (m/z) and saturation (H/C). While molecular composition of DOM remained similar in PRE sediments, the relative abundance of lignin-like substances decreased, with a concurrent increase in protein-like and lipid-like substances in DON and DOS from upper to lower PRE. Mechanistic analysis identified the joint influence of terrestrial OM, anthropogenic N/S inputs, and microbial processes in shaping the spatial gradients of DOM, DON, and DOS in PRE estuarine sediments. This study contributes valuable insights into the intricate spatial gradients and transformations of DOM, DON, and DOS within human-impacted estuarine sediments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Coastal environments are nitrogen (N) removal hot spots, which regulate the amount of land-derived N reaching the open sea. However, mixing between freshwater and seawater creates gradients of ...inorganic N and bioavailable organic matter, which affect N cycling. In this study, we compare nitrate reduction processes between estuary and offshore archipelago environments in the coastal Baltic Sea. Denitrification rates were similar in both environments, despite lower nitrate and carbon concentrations in the offshore archipelago. However, DNRA (dissimilatory nitrate reduction to ammonium) rates were higher at the offshore archipelago stations, with a higher proportion of autochthonous carbon. The production rate and concentrations of the greenhouse gas nitrous oxide (N2O) were higher in the estuary, where nitrate concentrations and allochthonous carbon inputs are higher. These results indicate that the ratio between nitrate and autochthonous organic carbon governs the balance between N-removing denitrification and N-recycling DNRA, as well as the end-product of denitrification. As a result, a significant amount of the N removed in the estuary is released as N2O, while the offshore archipelago areas are characterized by efficient internal recycling of N. Our results challenge the current understanding of the role of these regions as filters of land-to-sea transfer of N.
•The availability of bioavailable carbon defines nitrate reduction end-product.•Estuaries with low bioavailable organic carbon can release high amounts of N2O.•Nitrogen is recycled through DNRA in the archipelago areas.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Dissolved organic matter (DOM) is a complex mixture of molecules that constitutes one of the largest reservoirs of organic matter on Earth. While stable carbon isotope values (δ
C) provide valuable ...insights into DOM transformations from land to ocean, it remains unclear how individual molecules respond to changes in DOM properties such as δ
C. To address this, we employed Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to characterize the molecular composition of DOM in 510 samples from the China Coastal Environments, with 320 samples having δ
C measurements. Utilizing a machine learning model based on 5199 molecular formulas, we predicted δ
C values with a mean absolute error (MAE) of 0.30‰ on the training data set, surpassing traditional linear regression methods (MAE 0.85‰). Our findings suggest that degradation processes, microbial activities, and primary production regulate DOM from rivers to the ocean continuum. Additionally, the machine learning model accurately predicted δ
C values in samples without known δ
C values and in other published data sets, reflecting the δ
C trend along the land to ocean continuum. This study demonstrates the potential of machine learning to capture the complex relationships between DOM composition and bulk parameters, particularly with larger learning data sets and increasing molecular research in the future.
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•Field, petrographic, geophysical, chronological, elemental, isotopic evidence of a Wilson cycle in the Adamastor ocean realm.•Full oceanic cycle spatio-temporal distribution of rift, passive margin ...and orogenic basins, MORB/SSZ ophiolites, arc rocks.•Coherent succession of petrologically distinct subduction, collisional and post-collisional igneous suites over 150 Myrs.•Subduction polarity reversal model for Tonian-Cryogenian island arcs followed by Ediacaran continental-margin (Andean) arcs.•Scissor-shaped oceanic basin leads to connected inverted aulacogen/subduction-collision/complex accretionary orogen system.
Field, petrographic, geophysical, geochronological, elemental and isotopic data support the identification of distinct components of a Wilson cycle (rift-drift-subduction-collision-collapse) in the South Atlantic Brasiliano Orogenic System (Mantiqueira Province). The main lines of evidence are: 1) Tonian-Cryogenian ophiolite complexes; 2) Hundreds of Hf-Nd-Sr isotope determinations indicating a temporal trend of juvenile to mixed Tonian-Cryogenian-Ediacaran igneous rocks comprising expanded calc-alkaline, magnesian, metaluminous gabbro-tonalite-granodiorite-granite/basalt-dacite-andesite-rhyolite series, developed in island arcs and in continental-margin (Andean-type) arcs; 3) Cratonic-sourced conglomerate-diamictite-sandstone-pelite-carbonate successions deposited in Tonian-Cryogenian rift-passive margins fringing the paleocontinental borders, covered by orogenic basins with contrasting provenance from the arc systems; 4) Paired negative-positive Bouguer anomalies typical of suture zones with ophiolite-bearing accretionary prisms in the lower plate and arc systems in the upper plate; 5) Paired HP/HTmetamorphic belts associated with Ediacaran suture zones and retro-eclogites associated with Tonian subduction. Proposed intracontinental models for this region, both original and revisited, are based on the visual interpretation of restricted space for an oceanic realm and rely on calculations using presumed spreading and subduction rates. However, those do not account for a number of pre-, syn- and post-collisional modifications of the original paleogeography and for plate configurations over a curved planetary surface, with asynchroneity of extensional, accretionary and collisional events over thousands-of-km long orogenic fronts. Scissor-shaped oceanic basins are the rule rather than the exception, with connection of (i) an aulacogen to (ii) a partially enclosed gulf that is, in turn, connected to (iii) an open ocean with complex subduction systems. This configuration leads, after closure of the oceanic realm, to the gradation found in the South Atlantic Brasiliano Orogenic System, with (i) an inverted rift (Paramirim) connected to (ii) a confined orogen with a pre-collisional continental-margin Andean-type arc (Araçuaí), connected, in turn, to (iii) complex accretionary-collisional orogens (Ribeira and Dom Feliciano) with accreted juvenile pre-collisional island arc terranes. This arrangement characterizes, thus, a prime example of a typical subduction-collision orogenic system. The various lines of evidence from distinct fields coherently indicate a full Wilson Cycle with generation and consumption of the Adamastor oceanic lithosphere, followed by continental collisions, ultimately giving birth to the Gondwana paleocontinent.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Applying organic fertilizer is the main way to enhance soil fertility through the interfacial reaction between mineral and dissolved organic matter (DOM). However, the interfacial reaction between ...minerals and DOM may influence antimony(V) (Sb(V)) mobility in agricultural soils around antimony mines. In our study the ferrihydrite (Fh) was chosen as a representative mineral, to reveal the effect of its interaction with chicken manure organic fertilizer (CM-DOM) with Fh on Sb(V) migration. In this study, we investigated different organic matter molecular weights and C/Fe molar ratios. Our findings indicated that the addition of CM-DOM decreased the adsorption of Sb(V) by Fh and promoted the re-release of Sb(V) adsorbed on Fh. This effect was enhanced by increasing the C/Fe molar ratio. Fh mainly affects its interaction with Sb(V) through electrostatic gravitational interaction and ligand exchange, but the presence of CM-DOM weakens the electrostatic interaction between Fh and Sb(V) as well as competes with Sb(V) for the hydroxyl reactive site on Fh surface. In addition, the smaller molecular weight fraction (<10 kDa) of CM-DOM has higher aromaticity and hydrophobicity, which potentially leads to more intense competition with Sb(V) for the reaction sites on Fh. Therefore, the application of organic fertilizer may promote Sb(V) migration, posing significant risks to soil ecosystems and human health, which should be a concern in field soil cultivation.
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•The CM-DOM of low MW (<10 kDa) has higher aromaticity and hydrophobicity.•The interaction between Fh and CM-DOM decrease Fh surface potential by proton dissociation.•CM-DOM competed with Sb(OH)6- for surface hydroxyl active sites on Fh.•The low MW CM-DOM fractions showed significant weakening effect on Sb(V) immobilization by Fh.•The aromaticity and hydrophobicity components of CM-DOM competes with Sb(V) for active sites on Fh.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Ariano Suassuna (1927-2014) passou os últimos 30 anos de sua vida trabalhando no livro que chamava de “síntese” de toda a sua obra. O Romance de Dom Pantero no Palco dos Pecadores só veio a ser ...publicado postumamente em dezembro de 2017. Especula-se que um dos fatores que tornou longo o processo de escrita foi a busca pelo formato que permitisse a síntese almejada. Baseando-se em textos de autores como Azevedo (2007), Klinger (2008), Newton Junior (2017), Ravetti (2002), e Zumthor (2014), este trabalho investiga a importância da performance como solução para o projeto de síntese buscado por Suassuna em seu romance. Iniciamos por desvendar a figura do Dom Pantero, os heterônimos presentes no romance e o projeto da "ilumiara" de Suassuna para, em seguida, contextualizar o desenvolvimento de suas aulas-espetáculo, apresentações em que se fundiam duas de suas figuras performáticas: o palhaço e o professor. A importância do contar sertanejo e também a performance no objeto livro do Romance de Dom Pantero são em seguida abordadas.
Resumo O presente estudo tem como objetivo construir um diálogo a partir dos narradores de Memórias póstumas de Brás Cubas e Dom Casmurro, publicados por Machado de Assis, em 1881 e 1889, ...respectivamente. Para tanto, baseando-se nos estudos e na crítica construída entorno desses livros, em especial, nos textos de Souza (2006), Hansen (2008), Schwarz (2000) e Caldwell (2008), a análise partirá das relações entre os narradores-protagonistas com as duas figuras femininas de maior destaque nos romances, respectivamente, Virgília e Capitu. Desse modo, ambas são aproximadas das musas da Antiguidade (HAVELOCK, 1996; KRAUSZ, 2007), uma vez que fazem desses "homens comuns" enunciadores de seus passados, reconstrutores de inúmeros fragmentos que compõem ambos os romances.
Abstract The present study aims to build a dialogue from the narrators of Memórias Póstumas de Brás Cubas and Dom Casmurro, published by Machado de Assis, in 1881 and 1889, respectively. Therefore, based on studies and criticism built around these books, especially on the texts of Souza (2006), Hansen (2008), Schwarz (2000) and Caldwell (2008), the analysis will start from the relationships between the narrators-protagonists and the female figures in the novels, Virgília and Capitu, respectively. In this way, both are similar to the muses of Antiquity (HAVELOCK, 1996; KRAUSZ, 2007), since they make these "common men" enunciators of their pasts, reconstructs of countless fragments that make up the novels.
Microbial reduction of Fe(III) minerals is a prominent process in redoximorphic soils and is strongly affected by organic matter (OM). We herein determined the rate and extent of microbial reduction ...of ferrihydrite (Fh) with either adsorbed or coprecipitated OM by Geobacter sulfurreducens. We focused on OM-mediated effects on electron uptake and alterations in Fh crystallinity. The OM was obtained from anoxic soil columns (effluent OM, efOM) and includedunlike water-extractable OMcompounds released by microbial activity under anoxic conditions. We found that organic molecules in efOM had generally no or only very low electron-accepting capacity and were incorporated into the Fh aggregates when coprecipitated with Fh. Compared to OM-free Fh, adsorption of efOM to Fh decelerated the microbial Fe(III) reduction by passivating the Fh surface toward electron uptake. In contrast, coprecipitation of Fh with efOM accelerated the microbial reduction, likely because efOM disrupted the Fh structure, as noted by Mössbauer spectroscopy. Additionally, the adsorbed and coprecipitated efOM resulted in a more sustained Fe(III) reduction, potentially because efOM could have effectively scavenged biogenic Fe(II) and prevented the passivation of the Fh surface by the adsorbed Fe(II). Fe(III)–OM coprecipitates forming at anoxic–oxic interfaces are thus likely readily reducible by Fe(III)-reducing bacteria in redoximorphic soils.
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