Mobile Salt Research Articles

A facile and efficient strategy to enhance hydrophilicity of zwitterionic sulfoalkylbetaine type monoliths

In order to prepare zwitterionic HILIC monolithic columns with high polarity, the highly hydrophilic monomer N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA) and crosslinker N,N′-methylenebisacrylamide (MBA) were employed for developing a novel sulfoalkylbetaine type stationary phase. The polymerization parameters were systematically optimized in order to obtain a satisfactory performance for column permeability, mechanical stability, hydrophilicity, efficiency and selectivity. Compared to the previously reported poly(N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)ammonium betaine-co-ethylene dimethacrylate) (poly(SPE-co-EDMA)) monolith and the poly(SPDA-co-EDMA) monolith that we developed, a significantly enhanced hydrophilicity was obtained on the poly(SPDA-co-MBA) monolithic column, illustrated by the lowered critical composition of the mobile phase corresponding to the transition from the HILIC to the RP mode. Excellent permeability, reproducibility and stability were achieved on this optimized poly(SPDA-co-MBA) monolith. A column efficiency of 70,000plates/m was obtained for the analysis of bases at a linear velocity of 1.95mm/s. As expected, by studying the influence of mobile phase pH and salt concentration on their retention, a weak electrostatic repulsion interaction for negatively charged analytes was also observed at low organic solvent content on the poly(SPDA-co-MBA) monolithic column. The final optimized poly(SPDA-co-MBA) monolith exhibited good selectivity for a series of polar compounds, such as phenols, bases, benzoic acid derivatives, small peptides, urea and allantoin.

Systematic evaluation of retention behavior of carbohydrates in hydrophilic interaction liquid chromatography

A systematic evaluation of retention behavior of carbohydrates in hydrophilic interaction liquid chromatography (HILIC) was performed. The influences of mobile phase, stationary phase and buffer salt on the retention of carbohydrates were investigated. According to the results, the retention time of carbohydrates decreased as the proportion of acetonitrile in mobile phase decreased. Increased time of carbohydrates was observed as the concentration of buffer salt in mobile phase increased. The retention behavior of carbohydrates was also affected by organic solvent and HILIC stationary phase. Furthermore, an appropriate retention equation was used in HILIC mode. The retention equation lnk = a + blnC(B) + cC(B) could quantitatively describe the retention factors of carbohydrates of plant origin with good accuracy: the relative error of the predicted time to actual time was less than 0.3%. The evaluation results could provide guidance for carbohydrates to optimize the experimental conditions in HILIC method development especially for carbohydrate separation

Preparation and application of novel zwitterionic monolithic column for hydrophilic interaction chromatography

A novel zwitterionic hydrophilic porous monolithic stationary phase was prepared based on the thermal-initiated copolymerization of N,N-dimethyl-N-(3-methacryl-amidopropyl)-N-(3-(sulfopropyl)ammonium betaine and ethylene glycol dimethacrylate. A typical hydrophilic separation mechanism was observed at a highly organic mobile phase (ACN >60%) on this optimized zwitterionic hydrophilic interaction chromatography (HILIC) monolithic stationary phase. Good permeability, stability, and column efficiency were observed on the final monolithic column. Additionally, a weak electrostatic interaction for charged analytes was confirmed in analysis of six benzoic acids by studying the influence of mobile phase pH and salt concentration on their retention behaviors on the obtained zwitterionic HILIC monolithic column. The optimized zwitterionic HILIC monolith exhibited good selectivity for a range of polar test analytes.

Sodium chloride diffusion in sulfonated polymers for membrane applications

Sodium chloride permeability and sorption measurements were used to calculate average salt diffusion coefficients for charged, sulfonated polymers of interest for membrane applications. A sulfonated polysulfone random copolymer and two phase-separated, sulfonated styrenic pentablock copolymers were considered, and data for these materials were compared with those for an uncharged cross-linked poly(ethylene glycol diacrylate) hydrogel. The average salt diffusion coefficients reported for the block copolymers are apparent salt diffusion coefficients because the values have not been adjusted for the polymer’s phase separated morphology. The sodium chloride permeability of the uncharged hydrogel decreases by about 16% as upstream salt concentration increases from 0.01 to 1molL−1. This salt permeability change results from a decrease in the salt diffusion coefficient with increasing salt concentration because the polymer’s water content decreases as salt concentration increases (i.e., osmotic de-swelling). This decrease in salt diffusion coefficient is consistent with free volume theory, wherein a decrease in water content leads to a decrease in free volume, thereby decreasing the salt diffusion coefficient and, in turn, salt permeability. In contrast, the sodium chloride permeability of the charged polymers increases by more than an order of magnitude as upstream salt concentration increases from 0.01 to 1molL−1. This salt permeability increase is due to increases in both mobile salt sorption and diffusion coefficients with increasing salt concentration, despite the fact that water content (and, therefore, free volume) in the polymer decreases as salt concentration increases. Thus, the increase in salt diffusion coefficient with increasing salt concentration in the charged polymers results from factors (which are currently poorly understood) other than simply water uptake or free volume.

Sodium chloride sorption in sulfonated polymers for membrane applications

Ion sorption measurements were conducted to characterize sodium and chloride sorption in sulfonated polymers of interest for membrane applications. An uncharged polymer, based on cross-linked poly(ethylene glycol diacrylate), was included for comparison. The charged polymers included a sulfonated polysulfone random copolymer and two phase separated sulfonated styrenic pentablock copolymers. The sodium and chloride ion concentrations sorbed in these polymers were measured after polymer films had been equilibrated with 0.01–1.0molL−1 aqueous NaCl solutions at neutral pH. For the sulfonated polymers, cation sorption was measured using a polymer ashing technique and flame atomic absorption spectrophotometry. Anion sorption was measured using a desorption technique and ion chromatography. Polymer charge, i.e., sulfonation, influenced ion sorption. In general, salt sorption increased as water sorption increased in all polymers considered. In the uncharged polymer, the molar concentrations of sorbed sodium and chloride were equal to one another, as expected. However, the sulfonated polymers sorbed much more sodium than chloride ions due to ion exchange. The experimental mobile salt (i.e., anion) sorption data were fit to a model containing contributions from both Donnan exclusion and simple salt partitioning to the overall salt uptake by the polymer. In general, the influence of Donnan exclusion on anion (i.e., mobile salt) sorption in these cation exchange materials is reduced as water uptake increases, presumably due, in part, to dilution of the hydrated polymer’s sulfonate groups.

Salt deposition, loading and gravity drainage in the Campos and Santos salt basins

Abstract The southern Brazilian salt basin, comprising the three sub-basins Santos, Campos and Espirito Santo, was deposited over a pre-existing rifted basin with c. 1–2 km of relief bordered by an outer basin high that separated the basin from the conjugate African margin. The evaporites are interpreted to have been deposited very rapidly (<1 Ma) during the waning of extension. Deposition of salt caused rapid loading of the basin, so that further basin subsidence occurred and mobile salt drained from structurally higher zones into the subsiding basins. Seismic evidence indicates that downslope salt drainage occurred before any sediment overburden accumulated. Withdrawal synclines within salt units developed adjacent to diapirs, which have intruded the evaporite sequence, and salt extrusions are observed which were buried by later salts. The early movement of the salt probably contributed to significant fault reactivation and redistribution of salt load, so that the final half-graben salt fill reached up to 4.5 km thick where only 1–2 km of salt was originally deposited.

The Narrabeen Group in the east-central Sydney Basin: physical properties and interpretation

A mesoscale petrophysics and lithological logging study has been carried out on 413 core samples of the 623 m thick Narrabeen Group succession penetrated by the Eveleigh No. 1 diamond drillhole. Mass properties, magnetic susceptibilities, and electrical estimates of mobile salt (EC 1 : 5 tests) were measured. A physical properties analysis posits a 3-fold subdivision of the succession: basal fluvio-deltaic and alluvial, upper lacustrine, and topmost fluvio-deltaic. Each division has cyclic sedimentation but from different provenances. The analysis has proved useful in the correlation of the Narrabeen Group present in a series of drillholes in the eastern part of the exposed Sydney Basin.

Bacterial communities associated with a mineral weathering profile at a sulphidic mine tailings dump in arid Western Australia

We investigated bacterial community assemblages and functions down a hill slope contaminated by tailings from a volcanogenic massive sulphide mine in arid Western Australia. Weathering of waste rock, high in S and Fe, had resulted in a varying elemental dispersal down a face of the tailings hill. Bacterial community assemblage, characterised by PCR-DGGE fingerprinting, was significantly associated with electrical conductivity (E.C.) (ρ = 0.664; P < 0.01). Analysis of mobile salts showed that E.C. values were driven by ionic S, Zn, Cl and Al. The bacterial community assemblage was directly characterised across an E.C. gradient using an oligonucleotide microarray (PhyloChip). The dominant taxa at the site were Proteobacteria, Actinobacteria and Firmicutes; however, 37 phyla were detected. The most responsive taxa to variation in E.C. was Acidobacteria (negative correlation). Patterns of heterotrophic processes (BioLog analysis) were also best explained by variation in E.C. (ρ = 0.53; P < 0.01), showing a link between primary mineral weathering by lithotrophic bacteria and abiotic processes, and secondary biogeochemical processes by heterotrophic taxa. These data significantly broaden our knowledge of the bacteria present in metallomorphic ecosystems, establish that mobile phase elements are key drivers of community structure, and that primary biogeochemical cycling is directly influencing other geochemical interactions in the samples.

Preparation of zwitterionic polymeric monolithic columns for hydrophilic interaction capillary liquid chromatography

Porous zwitterionic monolithic columns based on photo-initiated copolymerization of N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)ammonium betaine and poly(ethylene glycol) diacrylate in a binary porogen system comprising isopropanol and decanol were prepared in 75-μm-id fused silica capillaries. The resulting monolith was evaluated by hydrophilic interaction chromatography. Inverse size-exclusion chromatography was used to characterize the pore structure of the resulting monolith. A typical hydrophilic interaction chromatography mechanism was observed when the organic content in the mobile phase was higher than 60%. Good separations of amides, phenols, and benzoic acids were achieved. An efficiency of 75,000 plates/m was obtained. The effects of mobile phase pH, salt concentration, and organic modifier content on retention were investigated. For polar-charged analytes, both hydrophilic interactions and electrostatic interactions contributed to the selectivity.

Monolithic capillary columns synthesized from a single phosphate-containing dimethacrylate monomer for cation-exchange chromatography of peptides and proteins

Monoliths containing phosphoric acid functional groups were synthesized from only one monomer, bis[2-(methacryloyloxy)ethyl] phosphate (BMEP), in 75-μm i.d. UV transparent fused-silica capillaries by photo-initiated polymerization for cation exchange chromatography of peptides and proteins. Various synthetic conditions, including porogen solvents, monomer concentration, and polymerization time, were studied. The hydrophobicities of the resulting monoliths were evaluated using propyl paraben under reversed-phase conditions and synthetic peptides under ion-exchange conditions. These monoliths exhibited low hydrophobicities and relatively low porosities due to their highly cross-linked structures. A dynamic binding capacity (lysozyme) of 73 mg/mL of column volume was measured using the best performing monolith. Synthetic peptides were eluted in approximately 30 min without addition of acetonitrile to the mobile phase, yielding a peak capacity of 28. Efficiencies of 52,900 plates/m for peptides and 71,000 plates/m for proteins were obtained under isocratic conditions. The effects of separation conditions, i.e., mobile phase pH and salt gradient rate, were studied. Good run-to-run reproducibility was achieved with a relative standard deviation (RSD) less than 1.5% for retention times of proteins. The column-to-column retention time reproducibility for peptides was less than 3.5% RSD. A monolithic column was used to follow the deamidation of ribonuclease A. The kinetics of deamidation were founded to be first order with a half life of 195 h. A cytochrome C digest was also separated using a linear gradient of sodium chloride.

Sulfoalkylbetaine‐based monolithic column with mixed‐mode of hydrophilic interaction and strong anion‐exchange stationary phase for capillary electrochromatography

A novel monolithic stationary phase with mixed mode of hydrophilic and strong anion exchange (SAX) interactions based on in situ copolymerization of pentaerythritol triacrylate (PETA), N,N-dimethyl-N-methacryloxyethyl N-(3-sulfopropyl) ammonium betaine (DMMSA) and a selected quaternary amine acrylic monomer was designed as a multifunctional separation column for CEC. Although the zwitterionic functionalities of DMMSA and hydroxy groups of PETA on the surface of the monolithic stationary phase functioned as the hydrophilic interaction (HI) sites, the quaternary amine acrylic monomer was introduced to control the magnitude of the EOF and provide the SAX sites at the same time. Three different quaternary amine acrylic monomers were tested to achieve maximum EOF velocity and highest plate count. The fabrication of the zwitterionic monolith (designated as HI and SAX stationary phase) was carried out when [2-(acryloyloxy)ethyl]trimethylammonium methylsulfate was used as the quaternary amine acrylic monomer. The separation mechanism of the monolithic column was discussed in detail. For charged analytes, a mixed mode of HI and SAX was observed by studying the influence of mobile phase pH and salt concentration on their retentions on the poly(PETA-co-DMMSA-co-[2-(acryloyloxy)ethyl]trimethylammonium methylsulfate) monolithic column. The optimized monolith showed good separation performance for a range of polar analytes including nucleotides, nucleic acid bases and nucleosides, phenols, estrogens and small peptides. The column efficiencies greater than 192 000 theoretical plates/m for estriol and 135 000 theoretical plates/m for charged cytidine were obtained.

Challenges in presalt depth imaging of the deepwater Santos Basin, Brazil

Several discoveries, such as Tupi, Bem-Te-Vi, Parati, and Guara, have been announced in Santos Basin off the coast of Brazil, mostly in presalt layers. These layers were well imaged by a salt-flood volume in 2003, but distortions in the base of salt (BOS) and presalt layers were still obvious. Therefore, a constant velocity model is not adequate to capture the velocity variation inside the salt bodies, which include mobile salt and evaporites. A depth migration with a complete salt model is necessary to correctly position the reservoir structures. In this paper, we discuss the challenges in building such a velocity model and share the lessons we learned while working on a data set from the deepwater Santos Basin.

Novel highly hydrophilic zwitterionic monolithic column for hydrophilic interaction chromatography

A novel zwitterionic hydrophilic porous poly(SPV-co-MBA) monolithic column was prepared by thermal co-polymerisation of 1-(3-sulphopropyl)-4-vinylpyridinium-betaine (4-SPV) and N,N'-methylenebisacrylamide (MBA). An HILIC/RP dual separation mechanism was observed on this optimised poly(SPV-co-MBA) monolithic column and the composition of the mobile phase corresponding to the transition from the HILIC to the RP mode was around 30% ACN in water. Higher hydrophilicity was achieved on this novel monolithic column compared to the poly(N,N-dimethyl-N-methacryloxyethyl-N-(3-sulphopropyl)ammonium betaine-co-ethylene dimethacrylate) monolithic column. Permeability studies showed slight swelling and/or shrinking with mobile phases of different polarity. As might be anticipated, a weak electrostatic interaction for charged analytes was also observed by studying the influence of mobile phase pH and salt concentration on their retention on the poly(SPV-co-MBA) monolithic column. The final optimised poly(SPV-co-MBA) monolith showed comparable selectivities to commercial ZIC-pHILIC phases for polar test analytes. Fast separation of five pyrimidines and purines was achieved in less than 1 min due to the high permeability of the monolithic column. Additionally, baseline separation of nine benzoic acid derivatives was also observed using either a pH or ACN gradient.

Temporal and spatial development of a gravity-driven normal fault array: Middle–Upper Jurassic, South Viking Graben, northern North Sea

Three-dimensional seismic and well data from the South Viking Graben, northern North Sea Basin, is used to investigate the temporal and spatial development of a gravity-driven normal fault array above an evaporite-rich detachment. Two moderate throw (500–900 m), Middle to Upper Jurassic normal faults (the Gudrun and Brynhild Faults) are developed within the study area. Both faults die-out laterally and tip-out upwards at different structural levels within the syn-rift succession. Both faults terminate downwards into Late Permian evaporites (Zechstein Group) and do not offset pre-evaporite basement units. This thin-skinned fault array developed in response to westwards tilting of the hangingwall of the South Viking Graben during Late Jurassic rifting, and consequent westward gliding and extensional break-up of units above the mechanically-weak evaporite horizon. Isochron mapping and well-based correlation of Middle to Upper Jurassic syn-rift units allow constraints to be placed on the temporal evolution of the fault array. Several stages of structural development are observed which document; (i) a period of relatively minor, early (i.e. pre-rift) halokinesis; (ii) variable spatial activity on individual faults within the array; and (iii) the progressive upslope migration of active faulting within the array as a whole. The progressive upslope migration of fault activity is interpreted to reflect progressive “unbuttressing” and extensional faulting of upslope, post-evaporite units. The overall structural style and kinematic evolution identified here shares many characteristics with both ‘ rift–raft tectonics’ documented in other rifts developed above an evaporitic sub-stratum and ‘ raft tectonics’ described from passive margin basins containing thick mobile salt or shale intervals. This style of fault array evolution differs from that observed in rifts lacking mobile layers at-depth and highlights the importance of these units in the structural development of rifts.

Novel zwitterionic polyphosphorylcholine monolithic column for hydrophilic interaction chromatography

A novel porous zwitterionic monolith was prepared by thermal co-polymerisation of 2-methacryloyloxyethyl phosphorylcholine (MPC) and ethylene glycol dimethacrylate (EDMA) within 100 μm I.D. capillaries. Mercury intrusion porosimetry, scanning electron microscopy (SEM), micro-HPLC (μ-HPLC), elemental analysis and ζ-potential analysis were used to evaluate the monolithic structure. No evidence of swelling or shrinking of the monolith in different polarity solvents was observed. A typical hydrophilic liquid chromatography (HILIC) mechanism was observed at high organic solvent content (acetonitrile >60%). The phosphorylcholine (PC) functionality has both a positively charged quaternary ammonium and a negatively charged phosphate group. For charged analytes, a weak electrostatic interaction was also observed by studying the influence of mobile phase pH and salt concentration on their retentions on the poly(MPC- co-EDMA) monolithic column. The optimised poly(MPC- co-EDMA) monolith showed very good selectivities for a range of polar test analytes, especially small peptides. This might be ascribed to the good biocompatibility of PC functionality. At low organic solvent content, baseline separation was also observed for a test mixture of seven alkylphenones by a reversed-phase separation mechanism.

Major structural elements of the Miocene section, Burgos Basin, northeastern Mexico

Major Miocene structural elements of the Burgos Basin include a regionwide detachment system that connects extensional fault systems throughout the basin with an active diapir belt downdip, a regionwide pattern of downthrown extensional rollover folds, pervasive secondary faults, and salt and shale diapiric masses in the eastern part of the basin. An interpretation of two-dimensional seismic data suggests that the Burgos Basin Miocene section can be divided into four structural domains: expanded zone, Lamprea trend, Corsair-Wanda trend, and diapir belt. The westernmost unexpanded zone is the footwall of the expanded system part of the basin, which overlies a domain of Oligocene extension. Remaining trends represent an extensional accommodation related to the basinward migration of mobile salt and shale, which has produced a relatively uniform structural style in the Miocene section. The structural style observed in the Burgos Basin appears to define a transitional zone between gravitational collapse in the offshore Laguna Madre-Tuxpan shelf to the south and salt-related raft tectonics of the south Texas Gulf Coast.

Protein Diffusion on Charged Membranes: A Dynamic Mean-Field Model Describes Time Evolution and Lipid Reorganization

As charged macromolecules adsorb and diffuse on cell membranes in a large variety of cell signaling processes, they can attract or repel oppositely charged lipids. This results in lateral membrane rearrangement and affects the dynamics of protein function. To address such processes quantitatively we introduce a dynamic mean-field scheme that allows self-consistent calculations of the equilibrium state of membrane-protein complexes after such lateral reorganization of the membrane components, and serves to probe kinetic details of the process. Applicable to membranes with heterogeneous compositions containing several types of lipids, this comprehensive method accounts for mobile salt ions and charged macromolecules in three dimensions, as well as for lateral demixing of charged and net-neutral lipids in the membrane plane. In our model, the mobility of membrane components is governed by the diffusion-like Cahn-Hilliard equation, while the local electrochemical potential is based on nonlinear Poisson-Boltzmann theory. We illustrate the method by applying it to the adsorption of the anionic polypeptide poly-Lysine on negatively charged lipid membranes composed of binary mixtures of neutral and monovalent lipids, or onto ternary mixtures of neutral, monovalent, and multivalent lipids. Consistent with previous calculations and experiments, our results show that at steady-state multivalent lipids (such as PIP2), but not monovalent lipid (such as phosphatidylserine), will segregate near the adsorbing macromolecules. To address the corresponding diffusion of the adsorbing protein in the membrane plane, we couple lipid mobility with the propagation of the adsorbing protein through a dynamic Monte Carlo scheme. We find that due to their higher mobility dictated by the electrochemical potential, multivalent lipids such as PIP2 more quickly segregate near oppositely charged proteins than do monovalent lipids, even though their diffusion constants may be similar. The segregation, in turn, slows protein diffusion, as lipids introduce an effective drag on the motion of the adsorbate. In contrast, monovalent lipids such as phosphatidylserine only weakly segregate, and the diffusions of protein and lipid remain largely uncorrelated.

Newly recognized eastern extension of the Nile deep-sea fan

A previously unreported easternmost segment of the Nile River deep-sea fan complex has been identified in the deep Levant Basin, offshore Israel, based mainly on a recently released, high-quality three-dimensional seismic data set. This segment is characterized by densely spaced seabed and subseabed turbidite channel complexes, generally fed from the region of the historically active northeastern Damietta and Pelusian branches of the Nile. This pattern suggests a previously unnoticeable symmetry in the modern channel distribution between the eastern and western branches of the deep-sea fan. The base of the Nile9s eastern deep-sea fan is determined by a NW-trending system of pre-Nile turbidite slope channels at the top of the Messinian evaporites. The overlying Pliocene–Holocene fan complex is further divided into two distinct stratigraphic units; a lower, stratified, sand-rich unit deposited in a basin-floor setting, and an upper heterogeneous, mud-rich unit consisting of downslope, mass transport, and hemipelagic sediments, with encased slope channel complexes richer in sand. Due to gravity gliding and spreading above the underlying thick, mobile Messinian salt, both stratigraphic units as well as the upper part of the Messinian salt layer are faulted and folded.

Initiation and growth of salt‐based thrust belts on passive margins: results from physical models

ABSTRACTScaled sandbox models simulated primary controls on the kinematics of the early structural evolution of salt‐detached, gravity‐driven thrust belts on passive margins. Models had a neutral‐density, brittle overburden overlying a viscous décollement layer. Deformation created linked extension–translation–shortening systems. The location of initial brittle failure of the overburden was sensitive to perturbations at the base of the salt. Salt pinch‐out determined the seaward limit of the thrust belt. The thrust belts were dominated by pop‐up structures or detachment folds cut by break thrusts. Pop‐ups were separated by flat‐bottomed synclines that were partially overthrust. Above a uniformly dipping basement, thrusts initiated at the salt pinch‐out then consistently broke landward. In contrast, thrust belts above a seaward‐flattening hinged basement nucleated above the hinge and then spread both seaward and landward. The seaward‐dipping taper of these thrust belts was much lower than typical, frictional, Coulomb‐wedge models. Towards the salt pinch‐out, frictional resistance increased, thrusts verged strongly seawards and the dip of the taper reversed as the leading thrust overrode this pinch‐out. We attribute the geometry of these thrust belts to several causes. (1) Low friction of the basal décollement favours near‐symmetric pop‐ups. (2) Mobile salt migrates away from local loads created by overthrusting, which reduces the seaward taper of the thrust belt. (3) In this gravity‐driven system, shortening quickly spreads to form wide thrust belts, in which most of the strain overlapped in time.

Morphostructure of the Egyptian Continental Margin: Insights from Swath Bathymetry Surveys

In the Eastern Mediterranean, offshore Egypt, the Nile continental margin is characterized by a large deep water turbiditic system known as the Nile Deep Sea Fan. This post-Miocene terrigenous construction covers an approximately 10 km-thick sedimentary pile, including 1–3 km of Messinian salt layers. Systematically collected swath bathymetric data proved to be the most powerful tool to discover, describe and study many sea floor features of this sedimentary construction which reflects competition between active tectonic, sedimentary, and geochemical processes. Gravity tectonics, triggered by underlying mobile salt layers, construction of channel-levee systems, the passage of turbidite flows, sedimentary slope failures at various scales, massive mud expulsions and fluid seepages are all interfering to shape the Nile Deep Sea Fan seabed.