Anoxic Conditions Research Articles

Paleoenvironmental Evolution and Organic Matter Enrichment Genesis of the Late Turonian Black Shale in the Southern Songliao Basin, NE China

AbstractThe Upper Cretaceous Qingshankou Formation black shales, deposited in the late Turonian (LTB shales), are the main source rocks of the Songliao Basin. The origins of organic matter enrichment of the shales is a contentious subject fuelling many ongoing debates. This study investigates the genesis of the organic matter‐rich shale by using molecular geochemistry. The LTB shales can be divided into three sections. The Section I shales were deposited in saline, stratified and anoxic water conditions, which are related to seawater incursion events. At least three episodic and periodic seawater incursion events were recognized during Section I shale deposition. The Section II shales deposited in brackish to fresh and deep lake‐level conditions with high primary productivity, which are related to lake‐level transgression. The Section III shales were deposited under fresh and slightly oxidized water conditions, which are related to lake‐level regression. Two organic matter enrichment models for the LTB shales are identified, that is, the seawater incursion model and the maximum lake‐level transgression sedimentation model, which act on different shale sections, both playing significant roles in the enrichment of organic matter.

Synergistic adsorption and degradation of sulfonylurea herbicides by biochar-supported nano zero-valent iron composites in in-situ soil remediation

The extensive and continuous application of sulfonylurea herbicide is crucial for weed management but has resulted in widespread non-point source pollution. In this study, nano zero-valent iron/biochar (nZVI/BC) was synthesized by using FeCl3-impregnated corn stalks under anoxic pyrolysis conditions, which was applied in the in-situ remediation of bensulfuron methyl (BSFM) and sulfometuron methyl (SMTM) polluted soil. The results show that nZVI/BC with a 2.7 ratio of Fe/C had the highest efficiency in removing sulfonylurea herbicides. The removal efficiencies of BSFM and SMTM by nZVI/BC were negatively correlated to initial concentrations of sulfonylurea herbicides and positively correlated to nZVI/BC addition amount in the soil. Moreover, nZVI/BC could remove 53 % of BSFM and 72 % of SMTM at the concentration of 5 mg/kg after 21 d, which was much higher than that of BC. Notably, the removal efficiency of BSFM by nZVI/BC reached 36 % within 7 d, while the removal efficiency of SMTM by nZVI/BC was up to 68 % even within 3 d. The adsorption of herbicides by nZVI/BC was mainly driven by chemical processes involving multilayer adsorption. Furthermore, the removal mechanisms of BMTM and SMTM by nZVI/BC also involved C = O and C–O groups and oxidation of nZVI to FeO and Fe3O4 along with the cleavage of the sulfonylurea bridge. This study provides a promising application of nZVI/BC in in-situ remediating sulfonylurea herbicide- polluted soil.

Widespread coastal upwelling along the marginal Yangtze Platform (South China) during the early Cambrian: Implications for hyper-enrichment of organic matter

Early Cambrian Earth history witnessed significant changes in marine environments and biological evolution contemporaneous with extensive accumulation of organic-rich shale. However, major factors controlling hyper-enrichment of organic matter (OM) of lower Cambrian shale deposits remain controversial. Black shale of the lower Cambrian Niutitang Formation (NTT) of the Marginal Yangtze Platform (South China) deposited during the Cambrian middle Age 2 are especially organic-rich, with total organic carbon (TOC) concentrations of as much as 13.0 wt%. Geochemical evidence suggests that cool, dry paleo-climatic conditions that prevailed on the Yangtze Platform during the Cambrian Fortunian-late Age 2, induced vigorous coastal upwelling. Paleo-productivity level assessments indicate that the magnitude of primary productivity contemporaneous with deposition of the NTT shale deposits exceeded that of modern upwelling systems (e.g., Peruvian Margin). The widespread occurrence of phosphate nodules within these deposits and decreased Co-EF × Mn-EF values of associated lower Cambrian black shale successions deposited along the margin of the Yangtze carbonate platform suggest extensive coastal upwelling. Widespread and strong coastal upwelling in tandem with elevated surface water primary productivity and anoxic (even euxinic) bottom water conditions are manifested by deposition of OM hyper-enriched black shale during Cambrian Fortunian to middle Age 2 time. However, weakened seasonal upwelling that appears to have prevailed during the late Cambrian Age 2 was accompanied by accumulation of NTT shale deposits of diminished TOC content. In summary, this study provides robust evidence of extensive coastal upwelling along the Marginal Yangtze Platform during early Cambrian time that favored accumulation of OM hyper-enriched shale. These results help to elucidate the distribution of high-quality lower Cambrian natural gas source rocks in South China.

Timing and origin of the Lomagundi-Jatuli Event: Insights from U[sbnd]Pb geochronology, C-O-Fe isotopes and REE compositions from the Jingshan Group, North China Craton

The Lomagundi-Jatuli Event (LJE) represents perhaps the largest and longest positive carbon isotope excursion of Earth history. However, the synchroneity, scale, and linkage of the LJE to Earth's early history of atmospheric oxygenation remain controversial. Strata of the Paleoproterozoic Jingshan Group of the North China Craton that preserve the isotopic record of the LJE excursion in marble layers and abundant graphite deposits provide an opportunity to elucidate the significance of the LJE. Carbon isotopic values (δ13CV-PDB) of the LJE based on analysis of 20 samples of the Lugezhuang Formation, lower Jingshan Group, range from −0.8 to +9.6 ‰ and display positive co-variance with stable oxygen isotope values (δ18OV-PDB). The positive carbon isotope excursion is constrained to 2140.6 ± 8.5 Ma (MSWD = 0.82, n = 25) based on magmatic zircon UPb geochronology of biotite granulite. Variation of facies-dependent carbon isotope values, the presence of graphite deposits of the Douya Formation, upper Jingshan Group, and the absence of a Ce anomaly in PAAS normalized REE patterns of marble samples suggest that the positive carbon isotope excursion is not linked to a marked increase of organic carbon burial and associated significant atmosphere oxygenation. Elevated concentrations of iron and PAAS-normalized middle REE enrichment of analyzed Jingshan Group marble samples point to anoxic and ferruginous oceanic conditions during accumulation of Jingshan Group carbonate. A positive Eu anomaly (average = 1.58), low La (average = 0.23), (Nd/Yb)N (average = 1.27), and Y/Ho (average = 36.6) anomalies, and negative iron isotope values (average δ56Fe = −0.12 ‰) are consistent with accumulation of Paleoproterozoic Jingshan Group carbonate in a restricted marine setting that was affected by high temperature hydrothermal fluids. Enrichment of the studied samples in heavy carbon isotope suggests elevated bio-productivity in the restricted, redox stratified marine setting in which Jingshan Group carbonate accumulated. Thus, it is likely that the positive stable carbon isotope excursion associated with Jingshan Group strata as well as other contemporaneous isotope excursions are local signals that are linked to a global perturbation of the carbon cycle.

Genome-resolved metagenomics revealed novel microbial taxa with ancient metabolism from macroscopic microbial mat structures inhabiting anoxic deep reefs of a Maldivian Blue Hole.

Blue holes are vertical water-filled openings in carbonate rock that exhibit complex morphology, ecology, and water chemistry. In this study, macroscopic microbial mat structures found in complete anoxic conditions in the Faanu Mudugau Blue Hole (Maldives) were studied by metagenomic methods. Such communities have likely been evolutionary isolated from the surrounding marine environment for more than 10,000 years since the Blue Hole formation during the last Ice Age. A total of 48 high-quality metagenome-assembled genomes (MAGs) were recovered, predominantly composed of the phyla Chloroflexota, Proteobacteria and Desulfobacterota. None of these MAGs have been classified to species level (<95% ANI), suggesting the discovery of several new microbial taxa. In particular, MAGs belonging to novel bacterial genera within the order Dehalococcoidales accounted for 20% of the macroscopic mat community. Genome-resolved metabolic analysis of this dominant microbial fraction revealed a mixotrophic lifestyle based on energy conservation via fermentation, hydrogen metabolism and anaerobic CO2 fixation through the Wood-Ljungdahl pathway. Interestingly, these bacteria showed a high proportion of ancestral genes in their genomes providing intriguing perspectives on mechanisms driving microbial evolution in this peculiar environment. Overall, our results provide new knowledge for understanding microbial life under extreme conditions in blue hole environments.

Reconstructing the redox environment of the Cambrian Harkless Formation, Nevada, USA: Navigating the effects of iron-rich clay minerals on the iron speciation redox proxy

Understanding the oxygenation of ancient oceans is critical for contextualizing evolutionary events throughout Earth's history. While there are many geochemical proxies available for evaluating paleoredox state, iron speciation is one of the most robust and widely applied recorders of local bottom water redox. The proxy uses a series of sequential extractions which are operationally designed to target redox active iron in different mineral groups, including carbonates, oxides, magnetite, and sulfides. However, clay minerals that contain iron are not specifically targeted but can be important reservoirs of redox active iron. These clay minerals are abundant during many times in Earth's history, so it is critical to understand how they are extracted during iron speciation and their impact on paleoenvironmental interpretations.Here we apply the iron speciation proxy in combination with other geochemical proxies (FeT/Al, Mn enrichments) and mineralogical analyses to determine local bottom water redox conditions during deposition of the early Cambrian Harkless Formation exposed near Gold Point, Nevada, USA. The Harkless Formation contains one of the last occurrences of archaeocyathan reefs before their extinction, thus studying the underlying strata can provide information about the environmental conditions which led to reef development. Iron speciation results indicate oxic to potentially anoxic conditions in the water column. The presence of FeT/Al enrichments, Mn depletion, and the Fe-rich redox sensitive clay minerals chamosite and glauconite suggest intermittent anoxia in the water column and porewaters during some intervals of Harkless deposition. Further, by combining iron speciation extractions with petrographic and x-ray diffraction analyses, we demonstrate that glauconite and chamosite were likely formed at or below the sediment water interface and are also not consistently or fully removed by the standard sequential iron reagents, as noted by previous work.The presence of these authigenic Fe-bearing clay minerals overall results in an underestimation of the proportion of redox active iron during deposition and early sediment diagenesis that may lead to incorrect environmental characterization. We therefore advocate for caution and careful examination of the mineralogy of samples when applying the iron speciation proxy, particularly when authigenic and/or early diagenetic iron-bearing clay minerals are suspected to be present. Based upon these findings, we suggest that the Harkless Formation experienced variable local bottom water redox conditions ranging from oxic to anoxic during deposition. Changes in the relative abundances of chamosite and glauconite may also indicate an increase in oxygenation up section, suggesting that local water column oxygenation played a role in archaeocyathan reef development.

Escape motility of multicellular magnetotactic prokaryotes.

Microorganisms often actively respond to multiple external stimuli to navigate toward their preferred niches. For example, unicellular magnetotactic bacteria integrate both oxygen sensory information and the Earth's geomagnetic field to help them locate anoxic conditions in a process known as magneto-aerotaxis. However, for multicellular magnetotactic prokaryotes (MMPs), the colonial structure of 4-16 cells places fundamental constraints on collective sensing, colony motility and directed swimming. To investigate how colonies navigate environments with multiple stimuli, we performed microfluidic experiments of MMPs with opposing magnetic fields and oxygen gradients. These experiments reveal unusual back-and-forth excursions called 'escape motility', in which colonies shuttle along magnetic field lines, punctuated by abrupt-yet highly coordinated-changes in collective ciliary beating. Through cell tracking and numerical simulations, we demonstrate that escape motility can arise through a simple magneto-aerotaxis mechanism, which includes the effect of magnetic torques and chemical sensing. At sufficiently high densities of MMPs, we observe the formation of dynamic crystal structures, whose stability is governed by the magnetic field strength and near-field hydrodynamic interactions. The results shed light on how some of the earliest multicellular organisms navigate complex physico-chemical landscapes.

Terrestrial response to the Early Cretaceous Weissert Event: Insights from carbon isotope records of organic matter and leaf wax n-alkanes in an inland East Asian lake

The Weissert Event (WE), a significant Early Cretaceous environmental disruption, is recognized globally in marine carbonate records for its positive carbon isotope excursion (CIE), organic matter (OM) enrichment, and widespread anoxia. However, records of its terrestrial impact are sparse. This study examines carbon isotope compositions (δ13C) from the lacustrine facies of North China's Dabeigou Formation (Yushuxia section, Luanping Basin). The synchronous positive CIEs of total organic carbon (TOC) and C27–C31n-alkanes within Members 2 to 3 of the Dabeigou Formation corroborate the Weissert Event, marking its first terrestrial observation in North China. Ratios of the isoprenoids pristane and phytane (Pr/Ph), Corg/P ratios and enrichment factors (EFs) of redox-sensitive trace metals (Mo and U) indicate transient anoxic conditions within a mainly oxic-suboxic setting from the late Valanginian to early Hauterivian, which were unfavorable for OM preservation. This highlights that although a global positive CIE occurred during the Weissert Event, anoxia and/or high TOC deposition in inland lakes were not inherent features.

Ecological risk of Cd and Cr in the black rock series should be noticed: Based on the study of enrichment mechanism, occurrence form in the Lower Cambrian Lujiaping formation

The heavy metals in soils developed from the black rock series originate from the parent rock, but their sources and enrichment mechanisms in the parent rock remain unclear. This study explores the enrichment mechanisms, occurrence forms, and ecological environmental effects of cadmium (Cd) and chromium (Cr) in the black rock series. Results revealed average concentrations of 1.15 mg/kg for Cd and 193.08 mg/kg for Cr. Cd showed moderate enrichment (CdEF=31.03), while Cr had slight enrichment (CrEF=4.42). Both metals were mainly in the residual fraction (44.22 % for Cd, 69.02 % for Cr), followed by the Fe-Mn oxide-bound fraction (24.07 % for Cd, 18.51 % for Cr). The Risk Assessment Code (RAC) indicated moderate risk for Cd (10 %≤RAC<30 %) and low risk for Cr (1 %≤RAC<10 %). The Secondary Phase to Primary Phase ratio (RSP) suggested mild Cd pollution (1 <RSP≤2) and no Cr pollution (RSP≤1). Cd poses a significant release risk, necessitating attention to its ecological safety. Hydrothermal and volcanic activities were primary sources of Cd, while TOC and volcanic activities influenced Cr. Anoxic conditions in the Lower Cambrian Ocean facilitated Cd and Cr enrichment. This study enhances understanding of heavy metal enrichment in black rock series and guides pollution management.

Microbial single-cell applications under anoxic conditions.

The field of microbiology traditionally focuses on studying microorganisms at the population level. Nevertheless, the application of single-cell level methods, including microfluidics and imaging techniques, has revealed heterogeneity within populations, making these methods essential to understand cellular activities and interactions at a higher resolution. Moreover, single-cell sorting has opened new avenues for isolating cells of interest from microbial populations or complex microbial communities. These isolated cells can be further interrogated in downstream single-cell "omics" analyses, providing physiological and functional information. However, applying these methods to study anaerobic microorganisms under in situ conditions remains challenging due to their sensitivity to oxygen. Here, we review the existing methodologies for the analysis of viable anaerobic microorganisms at the single-cell level, including live-imaging, cell sorting, and microfluidics (lab-on-chip) applications, and we address the challenges involved in their anoxic operation. Additionally, we discuss the development of non-destructive imaging techniques tailored for anaerobes, such as oxygen-independent fluorescent probes and alternative approaches.

Enrichment Mechanism of Polymetallic Elements at the Base of the Niutitang Formation in Southeast Chongqing

Polymetallic enrichment layers are commonly found at the base of the Lower Cambrian and extensively distributed across the Upper Yangtze Platform, yet their genetic models remain controversial. This study systematically collected samples from a typical section in the southeastern Chongqing region for mineral, organic, and inorganic analyses. It investigates the relationship between the abundance of various trace metal elements and organic matter at the base of the Niutitang Formation, as well as the vertical distribution characteristics of organic carbon isotopes and organic matter features. The results indicate that the Niutitang Formation shale exhibits a distinct three-part structure from bottom to top. Various metal elements are enriched in the lower interval, showing a close correlation between the abundance of polymetallic elements and the carbon isotopes of shale organic matter. The middle interval contains the highest TOC value and the lowest Ti/Al ratio, while the upper interval shows a significant decrease in organic matter abundance, with a clear positive correlation between the excess silicon content and Ti/Al ratio. Additionally, the mixing effect of deep-sea upwelling is the primary control on the formation of polymetallic enrichment layers in the lower interval, followed by the adsorption of organic matter under anoxic conditions. The sedimentary environment of the upper interval of the Niutitang Formation trends toward oxidation, with paleoclimate shifting toward colder and drier conditions, exhibiting aeolian sedimentary features that are unfavorable for the enrichment of trace metal elements. Consequently, upwelling is a key factor in the enrichment and mineralization of trace metal elements at the base of the Lower Cambrian in the Upper Yangtze region.

Emerging research on characterizing the potential of cable bacteria for CH4 mitigation

Methane (CH4) contributes an essential portion for global warming as a pivotal greenhouse gas. Microorganisms are identified as an effective way to mediate and control CH4 emission. Cable bacteria is a promising microorganism to mitigate CH4, however, the studies of distribution, abundance and function for CH4 reduction of cable bacteria in inland water still remain unclear. In this paper, we propose the probable CH4 mitigation metabolism within cable bacteria in anoxic condition, and present the future research directions about the application potential of cable bacteria in CH4 reduction. The viewpoint will help to understand the significant role of cable bacteria in CH4 mitigation and provide a potential way to control CH4 emissions in inland freshwater ecosystem.

Injectable, oxygen-releasing, thermosensitive hydrogel promotes vascularized bone formation with prolonged oxygen delivery and improved osteoinductivity

The failure or delay in healing of critical bone defects is primarily due to early local anoxic conditions and reduced osteogenic activity. In this research, we integrated calcium peroxide (CPO) embedded polycaprolactone (PCL) microspheres and osteoinductive nanoparticles (Hydroxyapatite/Laponite) into a thermosensitive hydrogel (Pluronic F127), thereby formulating an injectable oxygen-releasing osteogenic thermosensitive hydrogel. Notably, the oxygen-releasing microspheres (ORMs) within the composite hydrogel provide stable oxygen release for up to 21 days, ensuring the survival, migration, and bioactivity of both mesenchymal stem cells and endothelial cells under anoxic conditions. Additionally, the composite hydrogel significantly augments the osteogenic potential of bone marrow mesenchymal stem cells by providing a biomimetic microenvironment with the incorporation of nano-hydroxyapatite/laponite. Ultimately, the injectable composite hydrogel successfully stimulated bone regeneration within a cranial defect in a rat model after 8 weeks, with enhanced vascularization and bone quality. The engineered hydrogel provides a minimally invasive approach to stimulate bone regeneration with a sustained oxygen supply and osteogenic microenvironment provision, underlining its potential for treating critical bone defects.

Sulfate-mediated Fe(III) mineral reduction accelerates arsenic mobilization by a Desulfovibrio strain isolated from paddy soil

The biogeochemical cycling of arsenic (As) is often intertwined with iron (Fe) and sulfur (S) cycles, wherein Fe(III)- and sulfate-reducing bacteria (SRB) play a crucial role. Here, we isolated strain DS-1, a strictly anaerobic Fe(III)- and sulfate-reducing bacterium, from As-contaminated paddy soil. Using 16S rRNA gene sequence analysis, strain DS-1 was identified as a member of the genus Desulfovibrio. Strain DS-1 utilized energy derived from ferrihydrite reduction to support its cellular growth. Under anoxic sulfate-reducing conditions, the presence of strain DS-1 significantly increased As mobilization compared to sulfate-free conditions. Mechanistically, SRB-produced sulfide reacts with Fe(III) to form FeS, which disrupts Fe(III) minerals, thereby enhancing As release. These findings highlight the critical role of redox disequilibrium in As mobilization and suggest that SRB-produced sulfide may permeate to the rice rhizosphere, increasing As mobilization through Fe(III) reduction.

Performance of carbon and nitrogen removal in a system combining an aerobic trickling filter followed by two stages of vertical flow treatment wetland

Treatment wetland has become a reference in wastewater treatment, particularly for the treatment of domestic or agricultural effluent in rural areas. The AZOE process developed by the company SCIRPE is an optimised system of water treatment based on a conventional two-stage treatment wetlands with vertical hydraulic flow. A trickling filter has been added at the head of the system and filtration stages have been partially saturated to promote anoxic conditions. This study presents the monitoring of a complete pilot-scale AZOE system receiving real and continuous effluents. Effluents from two periods of the year are studied: autumn and spring when the organic load is higher. The performance of each treatment unit, as well as the total treatment unit is presented in this study. The main results show that i) the trickling filter consumes about half of the carbon load whatever the season but that nitrification is lower when the incoming organic load is higher ii) the first stage of filtration contributes a lot to denitrification thanks to the anoxic zones iii) the contribution of the second stage is lower but can increase in case of higher incoming load highlighting a safety role of the treatment. The continuous ammonium and nitrate data at the outlet of the first and second stages show a very characteristic dynamic of this system during the feeding period: a well-defined nitrate peak at the outlet of the first stage which is found on the second stage. The lack of carbon is pointed out as the most limiting factor to denitrification on the second stage.

Enhancing nitrogen removal by simultaneous nitritation and denitritation in a multi-cycle SBR with supplementation of solid carbon sources

Simultaneous nitritation and denitritation have the potential to significantly improve nitrogen removal in sewage treatment processes. However, their application in low-strength sewage treatment systems presents challenges. This study explored the impact of four solid carbon sources (SCSs) on N-removal via nitrite in a multi-cycle SBR with biocarriers. Results showed that both N-removal efficiencies and nitrite accumulation rates increased with higher COD/N ratios, indicating that high COD/N ratios can improve the competition between denitrifiers and nitrite-oxidizing bacteria for nitrite, leading to stable simultaneous nitritation and denitritation. The supplementation of SCSs further enhanced this high-efficiency N-removal process, with polybutylene succinate (PBS) and polycaprolactone (PCL) showing greater increases in N-removal via nitrite than poly-hydroxybutyrate (PHB) and poly-hydroxyalkanoate (PHA). Moreover, PBS showed the most significant increase in denitrification efficiency in anoxic conditions, while PHA was the most effective external SCS at a moderate level of dissolved oxygen. These findings suggest that the incorporation of external SCSs can facilitate the simultaneous nitritation and denitrification process in multi-cycle SBRs, underscoring the importance of selecting an appropriate SCS for optimizing nitrogen removal in sewage treatment projects.

Enhanced removal of nanoplastics from freshwater using in-situ synthesized and anchored nano-Fe3O4 via two-step ferrous oxidation

Magnetic separation is a promising strategy for removing nanoplastics (NPs) from water; however, it often requires complex processeses, such as synthesizing nano-Fe3O4 magnets and attaching them to specific carriers. This study presents an innovative and efficient strategy to in-situ synthesize and anchor nano-Fe3O4 onto polystyrene (PS) NPs through a two-step oxidation of ferrous ions, which significantly enhances NPs removal via magnetic separation. The two-step process involves initial alkalization of a ferrous aqueous solution under anoxic conditions, followed by oxidation in air. In the presence of PS spheres, nano-Fe3O4 forms in-situ on the PS surfaces, promoting sedimentation under a magnetic field. Results demonstrate that two-step ferrous oxidation achieves superior removal rates, with 99.32 % for 500 nm PS spheres (PS-500) and 93.16 % for 100 nm PS spheres (PS-100) using a low Fe2+ dosage of 0.1 mM. In contrast, the conventional one-step method, which simultaneously alkalizes and oxidizes ferrous sulfate in aerobic conditions, fails to form nano-Fe3O4 and results in low removal rates of only 56.49 % for PS-500 and 8.89 % for PS-100, respectively. Furthermore, the turbidity and residual Fe can be reduced to below 1 NTU and 0.1 mg/L by using two-step process, respectively, meeting drinking water safety and hygiene standards. This approach not only simplifies the magnetic nanomaterial preparation process but also substantially improves the NP removal efficiency, offering a promising solution for enhanced water treatment technologies and safer drinking water.

Impacts of submergence stress on rice plants and its adaptation: A review

The main aim of this review is to convey information in summarized form by compiling and interpreting the major findings of recent studies on the impacts of submergence stress on rice and tolerance mechanisms. Published research papers available in Google Scholar, Web of Science, and Pub Med, mainly by Elsevier and SpringerLink, were critically analyzed and summarized for the preparation of the manuscript. In rice, plant survival rates, growth, and development are adversely affected by submergence. Major findings documented that submergence alters the soil aeration and creates hypoxic and anoxic conditions, which results in low photosynthetic efficiency and sugar status in rice plants. Compared to a tolerant cultivar, a sensitive cultivar produces more ethylene and causes injury to the plant. Controlled underwater shoot elongation, higher conserved non-structural carbohydrates, and better hormonal regulation, especially ethylene and gibberellin, and abscisic acid, are the primary adaptive mechanisms of tolerant plants in submergence, which helps better recovery at the post-submergence stage, too. The Sub1 gene and the associated QTLs are crucial for the superior performance of tolerant cultivars in submergence. Any agronomic management practices that can reduce ethylene production and enhance the nutrient status of plants can alleviate the severity of submergence. Understanding the intricate relationship between submergence and rice plant response is essential, mainly how submergence affects the rice plant and its tolerance mechanism to develop resilient rice cultivars that can grow in flood-prone regions.

Seawater sulfate dynamics and a new tipping point in the Earth system

Seawater sulfate (SO42−) concentrations have changed by orders of magnitude in response to atmospheric and ocean redox dynamics throughout Earth’s history. A fundamental model that constrains seawater SO42− dynamics based on the principles of mass balance, however, is still lacking. Here, we used a dynamical systems approach to determine the effects of global source and sink strengths on seawater SO42− concentrations. Our stochastic analysis of the SO42− mass balance revealed two most probable seawater SO42− concentration ranges: one under widespread oceanic anoxic conditions with SO42− concentrations &amp;lt;1000 µM, and the other with SO42− concentrations around or above 10,000 µM under widely oxygenated ocean conditions. Swings between these two seawater SO42− concentration ranges are notably evident during the Phanerozoic Eon and developed in response to reoccurring oceanic anoxic events. We also identified a threshold for the extent of oceanic anoxia above which seawater SO42− concentrations collapse to &amp;lt;1000 µM, with corresponding impacts on global biogeochemical cycles, biology, and climate.

Neogene–Quaternary paleoenvironments and kerogen assessment of the NDO B-1 well, offshore Nile Delta, Egypt, Eastern Mediterranean: palynological evidence

Palynofacies and palynological investigations conducted on the Neogene–Quaternary succession from the NDO B-1 well, located in the offshore Nile Delta, Egypt, in the Eastern Mediterranean, suggest generally shallow marine (neritic) conditions. These environments are manifested by the overall palynofacies composition and the occurrence of dinoflagellate cysts (e.g., Spiniferites spp., Lingulodinium spp., Hystrichokolpoma spp., Homotryblium spp. and Selenopemphix spp.). Neritic environments are suggested for the lower and middle Miocene Sidi Salim, and the Pliocene to Pleistocene upper Kafr El Sheikh, El Wastani and Mit Ghamr formations, while shallower, coastal to inner neritic settings were interpreted for the late Miocene (Qawasim and Rosetta formations) and early Pliocene (Abu Madi and lower Kafr El Sheikh formations). Anoxic conditions existed during the deposition of the studied well succession, which can be seen from the occurrence of imprints of pyrite crystals and some types of oxygen-sensitive dinoflagellate cysts. The palynofacies fluctuated repeatedly between Amorphous Organic Matter (AOM)-dominated and phytoclast-dominated intervals, of kerogen types II and III, respectively. The spore coloration index (SCI) of indigenous thin-walled palynomorphs confirms thermally mature sediments, generative of dry gas and wet gas/condensates. Reworking during the deposition of the upper Sidi Salim, Qawasim and Rosetta formations is inferred from the occurrence of Cretaceous dinoflagellate cysts and pollen.