Strong Reducing Conditions Research Articles

Remediation of chlorinated ethenes, ethanes, and methanes in groundwater using carbon‐ and iron‐based electron donor

AbstractField‐scale pilot tests were performed to evaluate enhanced reductive dechlorination (ERD) of dissolved chlorinated solvents at a former manufacturing facility located in western North Carolina (the site). Results of the site assessment indicated the presence of two separate chlorinated solvent–contaminated groundwater plumes, located in the northern and southern portions of the site. The key chlorinated solvents found at the site include 1,1,2,2‐tetrachloroethane, trichloroethene, and chloroform. A special form of EHC® manufactured by Adventus Americas was used as an electron donor at this site. In this case, EHC is a pH‐buffering electron donor containing controlled release carbon and ZV Iron MicroSphere 200, a micronscale zero‐valent iron (ZVI) manufactured by BASF. Approximately 3,000 pounds of EHC were injected in two Geoprobe® boreholes in the saprolite zone (southern plume), and 3,500 pounds of EHC were injected at two locations in the partially weathered rock (PWR) zone (northern plume) using hydraulic fracturing techniques. Strong reducing conditions were established immediately after the EHC injection in nearby monitoring wells likely due to the reducing effects of ZV Microsphere 200. After approximately 26 months, the key chlorinated VOCs were reduced over 98 percent in one PWR well. Similarly, the key chlorinated solvent concentrations in the saprolite monitoring wells decreased 86 to 99 percent after initial increases in concentrations of the parent chlorinated solvents. The total organic carbon and metabolic acid concentrations indicated that the electron donor lasted over 26 months after injection in the saprolite aquifer. © 2009 Wiley Periodicals, Inc.

Cambrian Fossil Embryos from Western Hunan, South China

Abstract:The exquisitely preserved fossil embryos of Markuelia recovered from the limestones of the Middle Cambrian Haoqiao Formation and Upper Cambrian Bitiao formation in western Hunan, South China are described and illustrated in detail for the first time. A new species Markuelia elegans sp. nov. is established based mainly on embryos from the Upper Cambrian. A few of animal's resting eggs, which are comparable with those of the Ediacaran Doushantuo Formation, have been also found in the Upper Cambrian of western Hunan. The membrane of one egg from the uppermost Cambrian has been replaced by pyrite and the overgrowth of the pyrite crystals exhibits a unique inorganic pattern termed herein ‘Pseudoembryo’. The taphonomic setting in deeper water with possible strong reducing conditions promoted the excellent preservation for the Markuelia specimens. The study of Markuelia provides not only constraint on the anatomy, affinity, embryonic development and phylogenetic significance of this wormlike animal and but also opens a new window onto the evolution and development of the earliest animals.

Investigation of cobalt interference on lead hydride generation with tetrahydroborate(III) in the presence of hexacyanoferrate(III)

The interference of Co(II) on plumbane generation with tetrahydroborate in the presence of hexacyanoferrate(III) was studied with a new mechanism proposed to explain the interference. The products that were obtained, following reactions of a CoCl 2 solution with tetrahydroborate(III), which interfere with plumbane generation, were precipitated and investigated by inductively-coupled plasma-atomic emission spectrometry and -mass spectrometry (ICP-OES and ICP-MS). Batch experiments of the potentiometer analysis and pH determination were performed to investigate a mechanism of Co(II) interference on plumbane generation, the role of hexacyanoferrate(III) on plumbane generation, and the function of the masking agent on Co(II) interference. The preferentially formed nanoscale catalytic and magnetic cobalt borides in the redox system cause a potential for a strong reducing condition and induces the precipitation of Fe(III) and Pb(II) in the solution, which is counter to plumbane generation. Potassium thiocyanate/oxalic acid/1,10-phenanthroline, as the combined masking agent and working with hexacyanoferrate(III), decreases the amount of borides in the precipitates and acts as a kind of buffer of the redox potential, which maintains the conditions for plumbane generation. This hydride generation method has been applied to the direct determination of trace Pb in cobalt oxide standard reference materials with a detection limit of 0.3 µg L − 1 .

Changes in water quality following tidal inundation of coastal lowland acid sulfate soil landscapes

This study examines the remediation of surface water quality in a severely degraded coastal acid sulfate soil landscape. The remediation strategy consisted of partial restoration of marine tidal exchange within estuarine creeks and incremental tidal inundation of acidified soils, plus strategic liming of drainage waters. Time-series water quality and climatic data collected over 5 years were analysed to assess changes in water quality due to this remediation strategy. A time-weighted rainfall function (TWR) was generated from daily rainfall data to integrate the effects of antecedent rainfall on shallow groundwater levels in a way that was relevant to acid export dynamics. Significant increases in mean pH were evident over time at multiple monitoring sites. Regression analysis at multiple sites revealed a temporal progression of change in significant relationships between mean daily electrical conductivity (EC) vs. mean daily pH, and TWR vs. mean daily pH. These data demonstrate a substantial decrease over time in the magnitude of creek acidification per given quantity of antecedent rainfall. Data also show considerable increase in soil pH (2–3 units) in formerly acidified areas subject to tidal inundation. This coincides with a decrease in soil pe, indicating stronger reducing conditions. These observations suggest a fundamental shift has occurred in sediment geochemistry in favour of proton-consuming reductive processes. Combined, these data highlight the potential effectiveness of marine tidal inundation as a landscape-scale acid sulfate soil remediation strategy.

Structure of gallium‐doped mayenite and its reduction behaviour

AbstractThe isovalent Al/Ga substitution in mayenite has been studied by preparing the (Ca12Al14–x Gax O32)O1□5 series. Single phase compounds can be prepared up to x = 1 and the structure of this compound has been studied by joint Rietveld analysis of neutron and X‐ray powder diffraction data. The results showed that gallium substitutes aluminium, which provokes the expansion of the unit cell, as expected. (Ca12Al13GaO32)O1□5 has been treated at high temperature under strong reducing conditions to prepare an electride derivative. Unfortunately, instead the reduction leaving electrons into the mayenite cages, the Ga‐doped mayenite undergoes decomposition. The initial compound transforms to Ca3Al2O6, (Ca12Al14O32)O1□5 and amorphous Ga metal, which is likely deposited on the mayenite crystal surfaces. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Synthesis and Characterization of a New Family of Mixed Oxide−Proton Conductors Based on Tristrontium Oxysilicate

A new Sr3(Si1−xAlxO4)O1−x/2◻x/2 (0.0 ≤ x ≤ 0.2) oxysilicate series has been prepared, existing as a single phase for x ≤ 0.11. The evolution of the cell parameters was smooth along the series. The crystal structure of Sr3(Si0.9Al0.1O4)O0.95◻0.05 was determined from neutron powder diffraction data at room temperature. This compound crystallizes in the P4/ncc space group, Z = 4, with a = 6.9427(1) Å, c = 10.7992(1) Å, and V = 520.53(1) Å3. The Rietveld R values were RWP = 2.54% and RF = 1.33%. The Si4+/Al3+ aliovalent substitution is accompanied by oxygen vacancies for charge compensation. The crystal structure is described, as is a possible pathway for the “loosely bound” oxide anions that justifies the observed oxygen conductivity. Impedance data showed that the overall conductivity increased by more than 2 orders of magnitude from Sr3(SiO4)O to Sr3(Si0.89Al0.11O4)O0.945◻0.055. Further electrochemical characterization under various atmospheres (dry air, wet air, dry 5% H2 in Ar, and wet 5% H2 in Ar) and impedance data as a function of the oxygen partial pressure indicated that there was a significant proton contribution to the overall conductivity. The oxide ion transference numbers, determined using a modified electromotive force method, ranged from 0.98 to 0.95 under strong reducing conditions. A large p-type electronic contribution was also observed for Sr3(Si0.89Al0.11O4)O0.945◻0.055 under oxidizing conditions, decreasing the oxide ion transference number to ∼0.01 at 1173 K.

Identification of a Redox-sensitive Cysteine in GCP60 That Regulates Its Interaction with Golgin-160

Golgin-160 is ubiquitously expressed in vertebrates. It localizes to the cytoplasmic side of the Golgi and has a large C-terminal coiled-coil domain. The noncoiled-coil N-terminal head domain contains Golgi targeting information, a cryptic nuclear localization signal, and three caspase cleavage sites. Caspase cleavage of the golgin-160 head domain generates different fragments that can translocate to the nucleus by exposing the nuclear localization signal. We have previously shown that GCP60, a Golgi resident protein, interacts weakly with the golgin-160 head domain but has a strong interaction with one of the caspase-generated golgin-160 fragments (residues 140-311). This preferential interaction increases the Golgi retention of the golgin-160 fragment in cells overexpressing GCP60. Here we studied the interaction of golgin-160-(140-311) with GCP60 and identified a single cysteine residue in GCP60 (Cys-463) that is critical for the interaction of the two proteins. Mutation of the cysteine blocked the interaction in vitro and disrupted the ability to retain the golgin-160 fragment at the Golgi in cells. We also found that Cys-463 is redox-sensitive; in its reduced form, interaction with golgin-160 was diminished or abolished, whereas oxidation of the Cys-463 by hydrogen peroxide restored the interaction. In addition, incubation with a nitric oxide donor promoted this interaction in vitro. These findings suggest that nuclear translocation of golgin-160-(140-311) is a highly coordinated event regulated not only by cleavage of the golgin-160 head but also by the oxidation state of GCP60.

Temporal evolution of redox processes and free Cd dynamics in a metal-contaminated soil after rewetting

Soil testing procedures to address metals bioavailability currently use air-dried soil rewetted almost until saturation. Such practices may influence the redox state of soil and the related dynamics of metals. To assess this potential impact, a metal-contaminated soil was air-dried and rewetted to 90% water holding capacity. We monitored over a 21-day incubation period the temporal changes of soil redox potential and solution Cd concentration (either total or free). Other physico-chemical parameters were followed notably pH, ionic strength ( I) and the concentrations of NO 3 - , Mn, Fe and SO 4 2 - in solution. Soil redox potential showed the progressive establishment of strong reducing conditions in soil, in agreement with the temporal changes of NO 3 - , Mn, Fe and SO 4 2 - concentrations. It decreased by 13 pe units over the culture period leading to sulphate-reducing conditions (pe < −3) within only 21 days. Solution Cd concentration increased transitorily over the first 100–150 h of incubation (2-fold increase) in relation with the parallel increase in the concentration of competing cations for adsorption (Ca, Mg). It steeply decreased over the last 300 h of incubation (30-fold decrease) as a result of Cd precipitation as Cd sulphides. This biphasic evolution of Cd dynamics was related to the temporal changes of Cd resupply from the solid phase. Using the technique of DGT we described the kinetics of Cd resupply over time and needed to invoke the existence of two pools of Cd.

Removal of Pattern-breaking Sequences in Microtubule Binding Repeats Produces Instantaneous Tau Aggregation and Toxicity

Aggregated and highly phosphorylated tau protein is a pathological hallmark of Alzheimer's disease (AD) and other tauopathies. We identified motifs of alternating polar and apolar amino acids within the microtubule-binding repeats of tau which were interrupted by small breaking stretches. Minimal mutation of these breaking sequences yielded a unique instantly aggregating tau mutant containing longer stretches of polar/apolar amino acids without losing its microtubule-binding capacity. These modifications produced rapid aggregation and cytotoxicity with accompanying occurrence of pathologic tau phosphoepitopes (AT8, AT180, AT270, AT100, Ser(422), and PHF-1) and conformational epitopes (MC-1 and Alz50) in cells. Similar to pathological tau in the pretangle state, toxicity appeared to occur early without the requirement for extensive fibril formation. Thus, our mutant protein provides a novel platform for the investigation of the molecular mechanisms for toxicity and cellular behavior of pathologically aggregated tau proteins and the identification of its interaction partners.

グリーンラスト／フェライト循環処理法によるセレン汚染水の高度処理

Removal of selenium compound, especially hexavalent selenate ion, is one of the most difficult water treatment techniques and an effective method has not yet been established. In this research we propose a novel selenium removal process called Recycled Green rust/Ferrite Process, composed of an addition of Fe source, an alkaline conditioning of a concentrated slurry, an anaerobic chemical reaction stage, and a return of the settled slurry after solid-liquid separation. A mixed Fe2+-Fe3+ hydroxide compound, green rust (GR), reduces selenate to elemental selenium, while GR is consequently oxidized to magnetite Fe3O4. Therefore the black-colored magnetic slurry containing GR and magnetite contributes to the removal of selenate. Repeated batch-mode selenium removal tests showed that the residual selenium concentration gradually decreased with the number of batch test increased. Addition of ferrous sulfate or ferrous chloride (resulting Fe2+ concentration 600 mg/L) was eligible for Fe source for GR formation. Stable selenium removal was achieved when the number of batch test exceed 15 times. Optimum selenium removal ratio reached 99.95% where initial Se concentration 2.1mg/L decreased to 0.001mg/L. In contrast, little Se removal occurred when the combination of ferrous sulfate and elemental iron powder (each Fe2+ and Fe0 concentration was 300 mg/L) was used. During the reaction, oxidation-reduction potential leveled off -700mV vs Ag/AgCl and no dissolved oxygen was detected, indicating a strong reducing condition suitable for the reduction of selenate. Ninety percent of selenium disappeared as soon as the GR formed, and then selenate removal rate followed a first-order kinetics depending on the slurry concentration. These experimental results indicated that the proposed process served an advanced treatment technique for selenate-contaminated water.

グリーンラスト／フェライト循環処理法によるセレン汚染水処理の連続実証試験

In the previous reports we proposed a novel selenium removal process called Recycled Green rust/Ferrite Process, composed of an addition of ferrous ion source, an alkaline conditioning of a concentrated slurry, an anaerobic chemical reaction stage, and a return of the settled slurry after solid-liquid separation. This paper describes the results of continuous feeding test carried out in a pilot-scale plant with a feeding capacity 0.6 m3/h. Approximately 860-hour-feeding test was performed using the selenium-contaminated groundwater whose averaged selenium concentration of 0.88 mg/L. Selenium concentration in the effluent from thickener maintained less than 0.01 mg/L (selenium removal rate of 99%) until a net operating time reached 800 hours. For that period, oxidation-reduction potential leveled off -740mV vs Ag/AgCl electrode, and Fe2+/T-Fe ratio ranged from 0.61 to 0.68, indicating a strong reducing condition suitable for selenium removal. However, selenium removal deteriorated after 800h, when the liquid temperature fell below 17 degrees Celsius. In addition, results of the selenium concentrations were in qualitative agreement with the predicted values based on the simple reactor model using a continuous stirred tank reactor in series. These experimental findings demonstrated that our proposed process served a promising technique for selenium-contaminated water.

Distributions of C22–C30 even-carbon-number n-alkanes in Ocean Anoxic Event 1 samples from the Basque-Cantabrian Basin

The Ocean Anoxic Event 1 (OAE-1) in central sites of the Basque-Cantabrian Basin exhibits very reducing depositional conditions of sedimentation. These sedimentation events have left a distinct mixture of hydrocarbons that are represented by C22-C30 n-alkanes with a predominance of the even-carbon-number homologues, high relative proportions of squalane and C16-C24 n-alkylcyclopentanes predominated by n-undecyl-, n-tridecyl- and n-pentadecylcyclopentane. Other minor compounds encompass a series of C18-C21 n-alkylcyclohexanes and C18-C24 dimethyl n-alkylcyclohexanes maximized by the even-carbon-number homologues as well as iso- and anteiso-alkanes. This unusual distribution of n-alkanes in this environment provides a new case for comparison with previously reported hypersaline and phosphorite sedimentary deposits where the occurrence of similar n-alkane distributions was reported. In the present case, these major n-alkanes and squalane are indicative of transformation under strong reducing conditions. In contrast, the occurrence of the alkylcyclopentanes, irrespective of the presence of even-carbon-number n-alkanes or squalane, suggests that reductive cyclization of fatty acids is less dependent on strong reducing conditions.

Corrosion of carbon steel in compacted bentonite and its effect on neptunium diffusion under reducing condition

The corrosion of carbon steel and its effect on neptunium diffusion were studied by corrosion tests of carbon steel and neptunium diffusion tests under conditions designed with consideration of constituents of a repository for High-level Radioactive Waste disposal. The major constituents of the conditions were carbon steel, corrosion products pre-formed under aerobic conditions, compacted bentonite, reductant and a low-oxygen glove box. The corrosion tests were performed in the presence of water-saturated compacted bentonite. The neptunium diffusion tests were performed with and without carbon steel. The carbon steel and the bentonite were observed by taking photographs and analyzed by X-ray diffraction. The color of the corroded surface of the carbon steel changed from red/orange/black under aerobic conditions to a dark-green under reducing conditions. Portions of the bentonite changed their original color, pale-gray, to a brownish color after the test. Gas-induced cracks were also observed in some bentonite specimens. These changes were discussed combining thermodynamic predictions under the present experimental conditions. The results revealed that anaerobic corrosion of carbon steel occurred in the bentonite. The corrosion processes were also discussed. The corrosion rate of carbon steel was estimated to be ∼0.1 μm/year from iron profiles in the bentonite. This value was much lower than the conservative setting value 20 μm/year in the current performance assessment. The significant restriction in corrosion could be attributed to the presence of bentonite and corrosion products. Oxidation states of neptunium in the bentonite were investigated by thenoyltrifluoroacetone in xylene extraction technique. It was found that tetravalent neptunium accounted for 99% of the total neptunium in the presence of carbon steel and only 63% without. The results revealed that anaerobic corrosion of carbon steel could maintain strong reducing conditions to keep most tetravalent neptunium from being oxidized to pentavalent neptunium, thus effectively restraining migration of neptunium in the bentonite. The apparent diffusions were estimated to be in the order of 10 −15–10 −14 m 2/s for tetravalent neptunium and 10 −13–10 −12 m 2/s for the pentavalent. No significant effect of the corrosion products on neptunium sorption was found through comparing the apparent diffusion coefficients obtained in the diffusion with and without carbon steel. Corrosion of carbon steel under conditions relevant to the repository is essential for further studies, providing a confident and defensible value of corrosion rate for repository design. The effects of corrosion on radionuclide migration, especially redox-sensitive radionuclides in the buffer, should be considered for a reliable safety assessment of geological disposal.

The chemical behavior of sedimentary uranium in Authie Bay (France)

A general study on uranium present at trace levels in anoxic sediments derived from Authie Bay (in northern France) has been undertaken. For that purpose, concentrations of various uranium species in pore waters and recovered solutions (after mineralization of sediments) were determined by ICP-AES and ICP-MS. To access the extent of early diagenesis occurring in these sediments, reduced solid sulfur species were determined after their conversion into H2S gas following sequential extraction procedures. Our preliminary findings reveal that dissolved U(VI) precipitates rapidly with depth in pore waters certainly in the form of insoluble U(IV). Under stronger reducing conditions, new aqueous species [mostly and ] in which uranium is in oxidation state IV are formed in the pore water. Valuable interpretation of these particular properties of sedimentary U has necessitated a global examination of sediment biochemistry because of the influence of bacterial activities on the chemistry of Fe, Mn, S and more particularly U by metal-reducing bacteria.

Thermochemical stability of spinel (MgO·Al 2O 3) under strong reducing conditions

The thermochemical stability of the main refractory oxides and some of their compounds under strong reducing conditions has become increasingly important in recent years. In the present work, the formation, sintering and stability of magnesium–alumina spinel (MgAl 2O 4) under very low oxygen partial pressure were studied using Ellingham diagrams. Reduction processes of spinel at high temperatures 1500–1650 °C were discussed. The experimental treatments were carried out with spinel and equimolar mixtures of MgO and Al 2O 3. The effect of the oxygen partial pressure on stability of spinel was evaluated using different atmospheres: air ( P O 2 = 0.21 atm), CO/CO 2 (80/20), P O 2 < 10 −10 atm), CO ( P O 2 < 10 −15 atm) and C–CO ( P O 2 < 10 −20 atm). Finally, the results were compared with the experimental observations of spinel formation in MgO–C refractories with the addition of aluminium.

Sa Huynh and Cham potteries: microstructure and likely processing

Various techniques such as Raman spectroscopy, X-ray diffraction, and thermal expansion measurement have been applied to Sa Huynh (10th century BC–2nd century AD) and Cham (2–15th centuries AD) pottery findings from the excavations at Quang Ngai province (Central Viet Nam). The experimental results highlight the microstructure and technological processing of these potteries. Sa Huynh potteries technology is based on iron-rich clay-based body and feldspar fluxing agents. The firing is made in more or less strong reducing conditions. The Cham potteries were made from high-temperature fired silica-rich bodies covered with thin colourless to black–brown glazes.

Sa Huynh and Cham potteries: microstructure and likely processing

Various techniques such as Raman spectroscopy, X-ray diffraction, and thermal expansion measurement have been applied to Sa Huynh (10th century BC–2nd century AD) and Cham (2–15th centuries AD) pottery findings from the excavations at Quang Ngai province (Central Viet Nam). The experimental results highlight the microstructure and technological processing of these potteries. Sa Huynh potteries technology is based on iron-rich clay-based body and feldspar fluxing agents. The firing is made in more or less strong reducing conditions. The Cham potteries were made from high-temperature fired silica-rich bodies covered with thin colourless to black–brown glazes.

Effect of oxygen reduction on the optical conductivity ofLa0.75Ca0.25MnO3

Reflectivity measurements are used to obtain the optical conductivity of three ${\mathrm{La}}_{0.75}{\mathrm{Ca}}_{0.25}{\mathrm{MnO}}_{3\ensuremath{-}y}$ samples annealed under increasingly strong reducing conditions. All three samples are nearly saturated ferromagnets although their Curie temperatures fall progressively from ${T}_{c}=221\mathrm{K}$ to ${T}_{c}=187\mathrm{K}$ with maximum de-oxygenation. The presence of Drude absorption indicates that the unreduced and the slightly reduced samples are electrical conductors below ${T}_{c}.$ However, the most reduced sample manifests an insulatinglike optical conductivity at all temperatures. Thus, ferromagnetism and insulating behavior coexist in the most-reduced sample. This result contradicts the notion that mobile charge carriers of an electrically conducting manganite induce its ferromagnetism. Beyond Drude absorption, midinfrared and near-infrared absorptions are also observed. A midinfrared absorption band is present in all samples. The energy at its peak falls markedly with decreasing temperature. Moreover, near-infrared absorption is found in the nonconducting sample and in the high-temperature insulating phase of the conducting samples. The implications of these findings are discussed in terms of models for properties of doped manganites.

Molecular Cloning and Expression of Keratinocyte Proline-rich Protein, a Novel Squamous Epithelial Marker Isolated During Skin Development

We describe a novel rat cDNA named keratinocyte proline-rich protein (KPRP) isolated by RNA differential display during skin development. We determine that KPRP is expressed in stratified squamous epithelium, and its approximately 2.8-kb cDNA encodes a 699-amino acid protein with high proline content (19%). KPRP is an insoluble protein, similar to most epidermal terminal differentiation-associated proteins. Immunoblot of the protein lysate from keratinocytes, using strong reducing conditions, demonstrates two KPRP bands of approximately 76 and 55 kDa size. KPRP is expressed in stratified squamous epithelia of skin, tongue, and esophagus. The initiation of KPRP expression in fetal rat skin at E17, E18, E19, E20, and E21 was analyzed by reverse transcription-PCR. Fetal skin at E19 and later expresses KPRP. In situ hybridization of skin from E18, E19, and 4-day-old neonatal rats demonstrates that interfollicular and follicular keratinocytes express KPRP. Anti-KPRP antibody demonstrates KPRP protein localizes to all layers of stratified epithelia in skin, tongue, and esophagus. In cultured dermal keratinocytes, KPRP is diffusely distributed throughout the cytoplasm with denser staining adjacent to the nuclear and plasma membranes. Additionally, immunoreactive intracellular granules are observed during keratinocyte detachment from their plastic substrate. Rat KPRP has 89% homology to a mouse genomic DNA sequence and 56% homology to a human hypothetical protein. We conclude that KPRP may be a new epidermal terminal differentiation-related protein expressed in stratified squamous epithelia. KPRP is expressed by fetal dermal keratinocytes during late gestation and is a new marker of maturing epidermis during fetal skin development.

Stimulation of nitrogen fixation in refractory organic sediments by Caulerpa taxifolia(Chlorophyta)

Estimates of N2 fixation by substrata associated with the rhizophytic alga Caulerpa taxifolia were obtained using the acetylene reduction method. On average, growth of C. taxifolia enhanced rates of acetylene reduction in underlying dead sea grass sediments by a factor of 28, although the degree of enhancement was variable. The average rate of ethylene production was 3.96 nmol cm‐3 h‐1 (range = 2.5‐6.2 nmol cm‐3 h‐1). There was no apparent stimulation of N2 fixation in substrata collected close to a wastewater outlet. C. taxifolia appears to enhance N2 fixation by releasing photosynthetic product into the rhizosphere, mimicking the behavior of saltwater vascular plants. The excreted organic C activates the fermenting bacterial community, which in turn makes substrates available to the sulfate reducers. The associated microbial reactions create strong reducing conditions that favor N2 fixation, of which many sulfate reducers are capable. Nitrogen fixation can serve to reduce the N deficit that inhibits bacterial decomposition of refractory sea grass waste, thereby enhancing organic matter turnover and nutrient supply to the alga's rhizoids. This process likely assists C. taxifolia to proliferate upon refractory organic sediments in low‐nutrient seawater.