Solute Movement Research Articles

Designing artificial sodium ion reservoirs to emulate biological synapses

Emulating neurons/synapses in the brain is an important step to realizing highly efficient computers. This fact makes neuromorphic devices important emerging solutions to the limitations imposed by the current computing architecture. To mimic synaptic functions in the brain, it is critical to replicate ionic movements in the nervous system. It is therefore important to note that ions move easily in liquids. In this study, we demonstrate a liquid-based neuromorphic device that is capable of mimicking the movement of ions in the nervous system by controlling Na+ movement in an aqueous solution. The concentration of Na+ in the solution can control the ionic conductivity of the device. The device shows short-term and long-term plasticity such as excitatory postsynaptic current, paired-pulse facilitation, potentiation, and depression, which are key properties for memorization and computation in the brain. This device has the potential to overcome the limitations of current von Neumann architecture-based computing systems and substantially advance the technology of neuromorphic computing.

Upstream Dispersion in Solute Transport Models: A Simple Evaluation and Reduction Methodology.

This article outlines analytical solutions to quantify the length scale associated with "upstream dispersion," the artificial movement of solutes in the opposite direction to groundwater flow, in solute transport models. Upstream dispersion is an unwanted artifact in common applications of the advection-dispersion equation (ADE) in problems involving groundwater flow in the direction of increasing solute concentrations. Simple formulae for estimating the one-dimensional distance of upstream dispersion are provided. These show that under idealized conditions (i.e., steady-state flow and transport, and a homogeneous aquifer), upstream dispersion may be a function of only longitudinal dispersivity. The scale of upstream dispersion in a selection of previously presented situations is approximated to highlight the utility of the presented formulae and the relevance of this ADE anomaly in common transport problems. Additionally, the analytical solution is applied in a hypothetical scenario to guide the modification of dispersion parameters to minimize upstream dispersion.

Switching between positive and negative movement near an air/water interface through lateral laser illumination

The directional movement of an aqueous solution containing gold nanoparticles under laser irradiation (532 nm) through the vicinity of an air/water interface is reported. It is shown that unidirectional flow is generated along the path of light-travel when a laser is irradiated parallel to the interface. On the contrary, liquid flow toward the light source is caused when the incident angle of the laser is tuned so as to make the total reflection at an air/water interface. Such switching of the flow direction, positive or negative to the light propagation, was applied to the movement of mm-sized floating object, revealing that repetitive back and forth motion of the solid object is generated. This directional switching of photo-induced movement is interpreted by taking into account the flow caused by the spatial gradient of the surface tension due to the thermal effect of the incident laser. A numerical model with a Navier–Stokes-type equation reproduces the essential aspects of the switching of the direction observed in the present study.

Plant transporters involved in combating boron toxicity: beyond 3D structures.

Membrane transporters control the movement and distribution of solutes, including the disposal or compartmentation of toxic substances that accumulate in plants under adverse environmental conditions. In this minireview, in the light of the approaching 100th anniversary of unveiling the significance of boron to plants (K. Warington, 1923; Ann. Bot. 37, 629) we discuss the current state of the knowledge on boron transport systems that plants utilise to combat boron toxicity. These transport proteins include: (i) nodulin-26-like intrinsic protein-types of aquaporins, and (ii) anionic efflux (borate) solute carriers. We describe the recent progress made on the structure–function relationships of these transport proteins and point out that this progress is integral to quantitative considerations of the transporter's roles in tissue boron homeostasis. Newly acquired knowledge at the molecular level has informed on the transport mechanics and conformational states of boron transport systems that can explain their impact on cell biology and whole plant physiology. We expect that this information will form the basis for engineering transporters with optimised features to alleviate boron toxicity tolerance in plants exposed to suboptimal soil conditions for sustained food production.

THERMO ACID IMPULSING METHOD FOR OIL RECOVERY INCREASING

The injection rate created by the units does not provide uniform heating of the acid solution of thermal acid samples. The first portion of the solution is overheated, and the subsequent ones turn out to be insufficiently heated. Therefore, the efficiency of acid and thermal acid treatments of highly drained wells with low reservoir pressure is rather low. To increase the efficiency, a method of acid and thermal acid impulses was proposed, a methodology for its application was developed, and simple structures for the necessary underground and ground equipment for wells were developed (tip reactors and a universal wellhead). The method of thermal acid pulsation is based on the use of a special tip reactor. The reactor, the main components of which are the valve and the reactor itself, filled with magnesium chips, is lowered into the well on tubing until it stops in the bottom with its perforated nozzle-tip. The volume of solution poured into the tubing during thermal acid treatment by pulsation depends on their length and internal diameter. Usually it is assumed 1.2-2.0 m3. If in a well planned for thermal acid treatment by pulsation, the filter or some part of it turned out to be blocked by a sand plug, then they were preliminarily cleaned with a bailer without opening the sump. Thermal acid (as well as acid) well treatment by impulsing is carried out without the use of a pumping unit, which can significantly reduce costs. Accelerating the movement of the acid solution, heating the entire volume to the desired temperature and creating pressure (due to the weight of the column of solution) increase the depth of penetration and the effectiveness of the effect of acid on the formation. Based on the experiments, the following conclusions were drawn. 1) The process of thermal acid pulsation to achieve uniform heating of the acid solution is controlled by: a) increase in pumping pressure (the pressure is regulated by a column of liquid filled into the pipes); b) reduce the download speed; the speed of passage of the solution from the column of pumping pipes through the reactor with magnesium chips is initially much higher than the speed created by the injection of the acid solution by the unit; then, as the level of acid in the pipes drops, its outflow rate decreases; as a result, uniform heating of the acid solution to the required temperature is achieved. 2) Inhibition of HC1 with formalin and Unicol inhibits the reaction. However, only Unicol is able to stretch the reaction of HCI with magnesium for the required time, during which the entire process of pumping acid through nozzles proceeds. Thus, the most suitable acidic solution for thermal acid pulsation is 15 % HCl, inhibited by Unicol.

X‐ray computed tomography imaging of solute movement through ridged and flat plant systems

AbstractThe aim of this investigation was to experimentally compare the movement of a solute through soils with two field‐representative surface geometries: ridge and furrow surfaces versus flat surfaces. X‐ray computed tomography (XCT) imaging was undertaken to trace the movement of a soluble iodinated contrast medium, here used as an XCT‐visible analogue for field‐applied solutes, through soil columns with either a ridge and furrow or flat soil surface geometry. In addition to the soil surface geometry, the experimental treatments included the presence or absence of plants and surface water ponding. Experimental results were compared to existing numerical simulations adapted to represent the present experimental column systems. Similar infiltration patterns were observed in imaging results and the numerical simulations for most treatments. The experimental results suggest that plant roots present a significant localized effect to reduce the infiltration depth of solutes, particularly in planted ridges where the infiltration depth of the contrast medium was minimal. There is variability within the results because the number of replicates was limited to three due to the exploratory nature of the study (testing eight different treatments) and the cost and availability of XCT facilities capable of imaging such physically large samples. Discrepancies between the imaged infiltration depth of the solute and the numerical simulations are attributed to variation in plant root distribution and also spatial soil moisture, as measured using resistive soil moisture sensing. The results of this investigation elucidate the nature of solute movement through soil surface geometries, indicating that plant root water uptake can reduce solute infiltration depth, but surface ponding can negate this. These results suggest that soil surface shape, plant age and the timing of solute application with anticipated rainfall could be important considerations for reducing solute leaching and improving solute application efficiency.Highlights Investigating factors affecting solute infiltration in flat or ridge and furrow soil geometries. X‐ray CT imaging traces soluble contrast media movement in soil columns and is compared to modelling. Plant root water uptake can reduce solute infiltration depth, but surface ponding can negate this. Considering soil surface shape, rain and plant age in solute application could reduce leaching.

Potential influence of nonisothermality and concentration gradient on ball's Stokes motion in aqueous-glycerol solutions

The movement of a steel ball with a diameter of 4.37 mm in aqueous-glycerol solutions at room temperature is analyzed. It is shown that a slight difference between the initial ball's temperature and the solution temperature significantly affects the change in the ball speed. This is due to the strong dependence of the dynamic liquid viscosity on the temperature and water concentration. A study of the ball movement in aqueous-glycerol solution showed that it is necessary to mix it before the study. During long-term stationary storage, gravitational stratification occurs.For glycerin, which is open for a long time indoors, delamination is observed. Thus, the glycerol hygroscopicity leads to the accumulation in the lower part cylinder of about 7.4 vol. % water. This reduces the liquid viscosity by about 3 times regarding the viscosity of glycerin at the same temperature.An experimental study of changes in the ball speed was performed by digital video processing. The process of ball falling in the liquid was recorded using a video camera with a frequency of 30 frames per second.The results of the obtained values of aqueous-glycerol solutions viscosity were compared with the values of the obtained approximating formula.

Poroperm Properties of Rock Mass: A Case-Study of Upward Capillary Movement of Water Solutions in Vibroacoustic Treatment

The vibroacoustic effect on poroperm properties of rock mass in case of directed upward water movement has been studied experimentally. The relationships of percolation velocity and sound load at different pressure gradients are obtained for fine sand. The experiments prove feasibility of multiple increase of percolation velocity in upward capillary movement of water solutions.

Biological soil crusts determine soil properties and salt dynamics under arid climatic condition in Qara Qir, Iran

Biological soil crusts are a thin layer within the soil system but strongly determine the infiltration, runoff and water and solute movement. Little is known about the role of biological soil crusts on soil solute dynamics in arid ecosystems and the objective of this paper is to determine in Qara Qir rangeland how biological soil crusts control the water and salt distribution along the soil profile. Rainfall simulation experiments were carried out at five locations, and measurements of the soil at 0–5, 5–10, 10–20, 20–30, 30–50 and 50–80 cm depth were done before, 48 h and 21 days after the rainfall simulations. Soil particle size distribution, bulk density, water content, organic carbon and electrical conductivity were measured at each of the 270 samples (3 seasons × 3 times × 5 sites × 6 depths). Biological soil crusts increased soil organic carbon, soil water content, and infiltration rate; and biological soil crusts decreased soil bulk density, clay fraction, electrical conductivity, and other saline-sodic properties, especially in the upper layers (0–10 cm). Large pores in soils covered by biological soil crusts enhanced the preferential flows, infiltration and solute transport. Biological soil crusts not only directly affected the soil surface, but also influenced soil properties, and consequently determined spatio-temporal soil salinity distribution. Biological soil crusts act as a soil salinity reducing agent and contribute to the soil quality improvement under arid climatic conditions. Biological soil crusts can be considered as a soil conservation strategy and actively used in soil rehabilitation and ecosystems restoration.

Chemokine CCL28 treats oropharyngeal candidiasis through rapid membrane disruption

Abstract Candida albicans is a commensal organism that causes life-threatening or life-altering opportunistic infections. Treatment of these infections is limited by the paucity of anti-fungal drug classes. Antimicrobial peptides are a component of the immune response to fungi and promising agents for drug development. CCL28 is a CC chemokine that is abundant in saliva and has in vitro antimicrobial activity. In this study, we examine the spectrum of in vitro antimicrobial activity and the in vivo Candida killing capacity of CCL28 in oropharyngeal candidiasis (OPC), as well as the mechanism of anti-Candida activity. CCL28 is effective against multiple clinical strains of C. albicans, but less effective against C. glabrata. In the mouse model of OPC, application of wild type CCL28 reduces oral fungal burden in severely immunodeficient mice without causing excessive inflammation or altering tissue neutrophil recruitment. Both structured and unstructured CCL28 proteins show rapid and sustained fungicidal activity that is superior to clinical anti-fungal agents. Polyamine protein transporters are not required for CCL28 anti-Candida activity. Application of wild type CCL28 to C. albicans results in membrane disruption as measured by solute movement and enzyme leakage. Membrane disruption is reduced in CCL28 lacking the functional C-terminal tail. Our results indicate CCL28 functions in the immune response to disrupt fungal membranes and has potential for development as an anti-Candida therapeutic agent without inflammatory side effects.

Assessing the role of rainfall redirection techniques for arresting the land degradation under drip irrigated grapevines

Altering the soil surface features can potentially regulate water and solute movement processes in the soils, and reduce the accumulation of salts in the plant root zone. In this study, HYDRUS-2D was used consecutively for three years (2011–2014) to evaluate the potential impact of different rainfall redirection and water harvesting techniques such as no mounding or control (A), mid-row mounding (B), mid-row mounding covered with plastic (C), and plastic buried in the soil in mid-row (D) on water balance, root zone salinity dynamics, and salt balance in the soil in three grapevine producing regions (Loxton, McLaren Vale, and Padthaway) in South Australia. Simulations covered varied soil, climate, irrigation quality (0.3, 1.2, and 2.2 dS/m), and vine management conditions typical of each region. Seasonal transpiration (Tp), evaporation (Es), and drainage (Dr) accounted for 39–49, 26–44, and 17–25%, respectively, of the total drip irrigation applied to the vineyards across the three locations. Relative to the control, mounding mid-row soils (B) did not significantly alter the water balance at any site; adding an impermeable plastic layer to that mound (C) reduced Es (48–54%), and increased Dr (by two thirds) and Tp (1–16%). A tremendous ameliorative impact of mid-row mounding with plastic (C) was observed in the spatiotemporal salinity dynamics in the soils at all three locations (salt removal efficiency LEs > 1). An increased leaching fraction under the mid-row mounding with plastic (C) led to considerable (up to 14.6 t/ha) salts leaching from the crop root zone, which was double the other treatments. Buried plastic (D) showed slightly better outcomes than the control or mid-row mounding, particularly for seasonal salt leaching in heavy textured soils. Salt removal efficiency (LEs) > 1 in light- and medium-textured soils as compared to heavy-textured soils indicates better salt removal in the former soils. The results demonstrated that the mid-row mounding with plastic is an effective technique to reduce root zone salinity in the drip-irrigated horticultural crops.

Deletion of VDAC1 Hinders Recovery of Mitochondrial and Renal Functions After Acute Kidney Injury.

Voltage-dependent anion channels (VDACs) constitute major transporters mediating bidirectional movement of solutes between cytoplasm and mitochondria. We aimed to determine if VDAC1 plays a role in recovery of mitochondrial and kidney functions after ischemia-induced acute kidney injury (AKI). Kidney function decreased after ischemia and recovered in wild-type (WT), but not in VDAC1-deficient mice. Mitochondrial maximum respiration, activities of respiratory complexes and FoF1-ATPase, and ATP content in renal cortex decreased after ischemia and recovered in WT mice. VDAC1 deletion reduced respiration and ATP content in non-injured kidneys. Further, VDAC1 deletion blocked return of activities of respiratory complexes and FoF1-ATPase, and recovery of respiration and ATP content after ischemia. Deletion of VDAC1 exacerbated ischemia-induced mitochondrial fission, but did not aggravate morphological damage to proximal tubules after ischemia. However, VDAC1 deficiency impaired recovery of kidney morphology and increased renal interstitial collagen accumulation. Thus, our data show a novel role for VDAC1 in regulating renal mitochondrial dynamics and recovery of mitochondrial function and ATP levels after AKI. We conclude that the presence of VDAC1 (1) stimulates capacity of renal mitochondria for respiration and ATP production, (2) reduces mitochondrial fission, (3) promotes recovery of mitochondrial function and dynamics, renal morphology, and kidney functions, and (4) increases survival after AKI.

Gut-derived uremic toxin handling in vivo requires OAT-mediated tubular secretion in chronic kidney disease.

The role of the renal organic anion transporters OAT1 (also known as SLC22A6, originally identified as NKT) and OAT3 (also known as SLC22A8) in chronic kidney disease (CKD) remains poorly understood. This is particularly so from the viewpoint of residual proximal tubular secretion, a key adaptive mechanism to deal with protein-bound uremic toxins in CKD. Using the subtotal nephrectomy (STN) model, plasma metabolites accumulating in STN rats treated with and without the OAT inhibitor, probenecid, were identified. Comparisons with metabolomics data from Oat1-KO and Oat3-KO mice support the centrality of the OATs in residual tubular secretion of uremic solutes, such as indoxyl sulfate, kynurenate, and anthranilate. Overlapping our data with those of published metabolomics data regarding gut microbiome-derived uremic solutes - which can have dual roles in signaling and toxicity - indicates that OATs play a critical role in determining their plasma levels in CKD. Thus, the OATs, along with other SLC and ABC drug transporters, are critical to the movement of uremic solutes across tissues and into various body fluids, consistent with the remote sensing and signaling theory. The data support a role for OATs in modulating remote interorganismal and interorgan communication (gut microbiota-blood-liver-kidney-urine). The results also have implications for understanding drug-metabolite interactions involving uremic toxins.

Construction Solutions to Prevent Development of Secondary Cataract After Intraocular Lenses Implantation

Background. The development of secondary cataract after implantation of an intraocular lens (IOL) as a result of migration and reproduction of residual epithelial cells after phacoemulsification occurs in 45–78% of patients. The currently used IOL models do not adequately protect the posterior part of the lens capsule and the front surface of the lens from the deposition of epithelial cells on them. Objective. The aims of the paper are as follows: (1) modeling the process of development of secondary cataract due to proliferation, migration and metaplasia of residual epithelial cells (E-LEC); (2) evaluation of existing technical solutions to combat clouding of the lens capsule (CLC), secondary cataract, after implantation of IOL; (3) development of original technical approach to solving the problem of CLC with next modeling; (4) conducting an experiment to study the movement of a dye solution in an extracted pig's eye lens, implanted with a Support OP lens based on the data obtained during simulation. Methods. To model the migration of epithelial cells, the COMSOL Multiphysics 5.4 software environment and the Fluid flow library were used. For computer analysis, IOL of our own design and the lens of an American company were taken. During the simulation, it was taken into account that cells of a polygonal or oval shape have sizes from 48 to 142 μm and a constant propagation velocity of 10 - 4 m/s. The main attention was paid to the spread of epithelial cells not only towards the posterior wall of the lens capsule, but also to the front surface of the lens itself. After carrying out computer modeling, the results of which have been repeatedly confirmed, an experiment was carried out in which a capsule bag of a pig's eye lens was implanted with an implanted IOL of its own design. An aqueous dye solution, applied under a pressure not exceeding the penetration strength of the lens capsule, imitated the movement of epithelial cells. The study was conducted in compliance with the ARRIVE guidelines. Results. The simulation showed that the use of the IOL sharp edge design just partially protects the back wall of the capsule from the growth of epithelial cells (E-cells) on it, despite the fact that the lens is made of hydrophobic acrylic. This IOL doesn’t tightly contact with the back wall of the capsule and therefore the migration of lens epithelial cells in this direction is possible. The front of the lens also remains vulnerable to fibrous hyperplasia, which leads not only to visual impairment, but also to its complete loss. The proposed volume-replacing IOL of its own design, which has a sharp edge, which provides close contact with the lens capsule, a groove-trap for migrating cells, and in the front of the elements for suture fixation. Conclusions. The study revealed a number of factors that need to be addressed to prevent the development of secondary cataract. The intraocular lens must be made of biocompatible material, for the full tension of lens capsule, it is necessary that the haptic is angulated, the optical part should include at least one of the elements (a sharp edge or a special side). Based on this, the proposed approach takes into account the problems described in the article and includes the above elements and a special groove-trap for epithelial cells. Modeling and experimental testing of the proposed option confirmed its effectiveness.

Minimization of real power loss by enhanced teaching learning based optimization algorithm

<p class="Abstract">This paper presents an Enhanced Teaching-Learning-Based Optimization (ETLBO) algorithm for solving reactive power flow problem. Teaching-learning process is an iterative process where in the continuous interaction takes place for the transfer of knowledge. Movements of trial solutions will investigate the internally final stages. Up gradation of the algorithm has been done through by adding weight in the learner values. Projected ETLBO algorithm has been tested in standard IEEE 57,118 bus systems and power loss has been reduced efficiently.</p>

Bi-allelic JAM2 Variants Lead to Early-Onset Recessive Primary Familial Brain Calcification

Primary familial brain calcification (PFBC) is a rare neurodegenerative disorder characterized by a combination of neurological, psychiatric, and cognitive decline associated with calcium deposition on brain imaging. To date, mutations in five genes have been linked to PFBC. However, more than 50% of individuals affected by PFBC have no molecular diagnosis. We report four unrelated families presenting with initial learning difficulties and seizures and later psychiatric symptoms, cerebellar ataxia, extrapyramidal signs, and extensive calcifications on brain imaging. Through a combination of homozygosity mapping and exome sequencing, we mapped this phenotype to chromosome 21q21.3 and identified bi-allelic variants in JAM2. JAM2 encodes for the junctional-adhesion-molecule-2, a key tight-junction protein in blood-brain-barrier permeability. We show that JAM2 variants lead to reduction of JAM2 mRNA expression and absence of JAM2 protein in patient’s fibroblasts, consistent with a loss-of-function mechanism. We show that the human phenotype is replicated in the jam2 complete knockout mouse (jam2 KO). Furthermore, neuropathology of jam2 KO mouse showed prominent vacuolation in the cerebral cortex, thalamus, and cerebellum and particularly widespread vacuolation in the midbrain with reactive astrogliosis and neuronal density reduction. The regions of the human brain affected on neuroimaging are similar to the affected brain areas in the myorg PFBC null mouse. Along with JAM3 and OCLN, JAM2 is the third tight-junction gene in which bi-allelic variants are associated with brain calcification, suggesting that defective cell-to-cell adhesion and dysfunction of the movement of solutes through the paracellular spaces in the neurovascular unit is a key mechanism in CNS calcification.

Deciphering aquaporin regulation and roles in seed biology.

Seeds are the typical dispersal and propagation units of angiosperms and gymnosperms. Water movement into and out of seeds plays a crucial role from the point of fertilization through to imbibition and seed germination. A class of membrane intrinsic proteins called aquaporins (AQPs) assist with the movement of water and other solutes within seeds. These highly diverse and abundant proteins are associated with different processes in the development, longevity, imbibition, and germination of seed. However, there are many AQPs encoded in a plant's genome and it is not yet clear how, when, or which AQPs are involved in critical stages of seed biology. Here we review the literature to examine the evidence for AQP involvement in seeds and analyse Arabidopsis seed-related transcriptomic data to assess which AQPs are likely to be important in seed water relations and explore additional roles for AQPs in seed biology.

Inferring the role of pit membranes in solute transport from solute exclusion studies in living conifer stems.

The functional role of pits between living and dead cells has been inferred from anatomical studies but amassing physiological evidence has been challenging. Centrifugation methods were used to strip water from xylem conduits, permitting a more quantitative gravimetric determination of the water and solid contents of cell walls than is possible by more traditional methods. Quantitative anatomical evidence was used to evaluate the water volume in xylem conduits and the water content of living cells. Quantitative perfusion of stems with polyethylene glycol of different molecular weight was used to determine the solute-free space. We measured the portioning of water and solute-free space among anatomical components in stems and demonstrated that lignin impeded the free movement of solutes with molecular weight >300. Hence, movement of large solutes from living cells to xylem conduits is necessarily confined to pit structures that permit transmembrane solute transport via primary walls without lignin. The functional role of pits was additionally indicated by combining data in this paper with previous studies of unusual osmotic relationships in woody species that lack pits between dead wood fibers and vessels. The absence of pits, combined with the evidence of exclusion of solutes of molecular weight >300, explains the unexpected osmotic properties.

Chemical components, physiological functions and regulation mechanism of plant Casparian strips

Casparian strips are diagnostically modified structure mainly appeared in the endodermis, in which the radial parts of the cell walls are characterized by the deposition of lignin and suberin in the primary cell wall. As a barrier to the apoplastic movement of solutes from the cortex to the stele, Casparian strips are essential for the exclusion of salts and pathogens, selective nutrient uptake, and many other processes. With the development of biochemical analysis techniques and genetic research methods, the research in Casparian strips was increasing and has accumulated a large number of data. In this paper, we summarize the research progress in cytological structure, development processes, chemical components of Casparian strips. We focus in particular on recent advances in physiological functions and the regulation mechanism of Casparian strips during developmental processes and the response to different environmental conditions. This review can provide significant information for further investigation on the development of Casparian strips.

Bioturbation may not always enhance the metabolic capacity of organic polluted sediments

Marine sediments are a major sink of organic matter, playing a crucial role in the global cycling of major elements. Macrofauna, through the reworking of particles and movement of solutes (bioturbation), enhances oxic conditions and the sediment metabolic capacity. Increases in the inputs of organic matter can lead to profound changes in the seabed and impact benthic ecological functions. Through a microcosm experiment, the effect of bioturbation of the polychaete Lumbrineris latreilli on biogeochemical fluxes under scenarios of increasing loads of organic matter was quantified. We found that bioturbation can buffer the negative consequences of anoxic conditions produced by organic enrichment, preventing the build-up of toxic by-products derived from anaerobic metabolic pathways by maintaining oxic conditions. However, the maintenance of oxic conditions by bioturbation is at the expense of limiting the sediment metabolic capacity. The maintenance of oxic conditions may limit anaerobic metabolic pathways, and consequently, the metabolic capacity of sediment. Thus, under organic matter pollution conditions, bioturbation may lessen the metabolic capacity of the sediment.