Composition Of Skeletons Research Articles

The influence of seawater pCO2 and temperature on the amino acid composition and aragonite CO3 disorder of coral skeletons

Coral skeletons are composites of aragonite and biomolecules. We report the concentrations of 11 amino acids in massive Porites spp. coral skeletons cultured at two temperatures (25 °C and 28 °C) and 3 seawater pCO2 (180, 400 and 750 µatm). Coral skeletal aspartic acid/asparagine (Asx), glutamic acid/glutamine (Glx), glycine, serine and total amino acid concentrations are significantly higher at 28 °C than at 25 °C. Skeletal Asx, Glx, Gly, Ser, Ala, L-Thr and total amino acid are significantly lower at 180 µatm seawater pCO2 compared to 400 µatm, and Ser is reduced at 180 µatm compared to 750 µatm. Concentrations of all skeletal amino acids are significantly inversely related to coral calcification rate but not to calcification media pH. Raman spectroscopy of these and additional specimens indicates that CO3 disorder in the skeletal aragonite lattice is not affected by seawater pCO2 but decreases at the higher temperature. This is contrary to observations in synthetic aragonite where disorder is positively related to the aragonite precipitation rate mediated by either increasing temperature (this study) or increasing Ω (this study and a previous report) and to the concentration of amino acid in the precipitation media (a previous report). We observe no significant relationship between structural disorder and coral calcification rate or skeletal [amino acid]. Both temperature and seawater pCO2 can significantly affect skeletal amino acid composition, and further work is required to clarify how environmental change mediates disorder.

Correlative geochemical imaging of Desmophyllum dianthus reveals biomineralisation strategy as a key coral vital effect

The chemical and isotopic composition of stony coral skeletons form an important archive of past climate. However, these reconstructions are largely based on empirical relationships often complicated by “vital effects” arising from uncertain physiological processes of the coral holobiont. The skeletons of deep-sea corals, such as Desmophyllum dianthus, are characterised by micron-scale or larger geochemical heterogeneity associated with: (1) centres of calcification (COCs) where nucleation of new skeleton begins, and (2) fibres that thicken the skeleton. These features are difficult to sample cleanly using traditional techniques, resulting in uncertainty surrounding both the causes of geochemical differences and their influence on environmental signals. Here we combine optical, and in-situ chemical and isotopic, imaging tools across a range of spatial resolutions (~ 100 nm to 10 s of μm) in a correlative multimodal imaging (CMI) approach to isolate the microstructural geochemistry of each component. This reveals COCs are characterised by higher organic content, Mg, Li and Sr and lower U, B and δ11B compared to fibres, reflecting the contrasting biomineralisation mechanisms employed to construct each feature. CMI is rarely applied in Environmental/Earth Sciences, but here we illustrate the power of this approach to unpick the “vital effects” in D. dianthus, and by extension, other scleractinian corals.

Effect of initial pore water content and salinity on the resistivity of methane hydrate-bearing fine sediments

Methane hydrates are widely distributed in the soft silty-clayey soils of continental margin sediments. The resistivity method is generally used to detect their distribution state and monitor their kinetic reaction process. However, there are some major details to be elaborated on as to the occurrence state and the evolution of key characteristic parameters. Based on the kinetic reaction experiment under different lithological conditions (initial water content and pore water salinity), this research records the changing resistance of natural sand porous medium system during the cooling formation of hydrates by in-situ measurement. The Archie formula is further used to study the influencing factors of the resistance of hydrate-bearing sediments and how the resistance changes during hydrate formation. The results demonstrate that these two lithological parameters can significantly affect the resistivity of the hydrate-bearing natural sand porous media system. It is found that within a certain range, NaCl in pore water will inhibit the formation reaction of hydrates, while an increase of initial water content will enhance the hydrate production amount in the system. With the hydrate formation in the pores, the porosity and skeleton composition of the natural sand porous medium change as well, coupled with the salt-removing effect, which further changes the system resistivity. During hydrate formation, the system resistivity changes regularly in the cooling stage, hydrate nucleation stage, and hydrate formation stage. Our study systematically considers the influence of these geological parameters on resistivity characterization at different reaction stages during the formation of natural hydrates. Thus, it can serve as a technical reference for hydrate reservoir logging and other related issues.

Addition of chitosan to Calcium-Alginate Membranes for Seawater NaCl Adsorption

<abstract> <p>Initial research was focused on the production of calcium-based alginate-chitosan membranes from coral skeletons collected from the Gulf of Prigi. The coral skeleton's composition was analyzed using XRF, revealing a calcium oxide content ranging from 90.86% to 93.41%. These membranes showed the significant potential for salt adsorption, as evidenced by FTIR analysis, which showed the presence of functional groups such as -OH, C = O, C-O, and N-H involved in the NaCl binding process. SEM analysis showed the particle size diameter of 185.96 nm, indicating a relatively rough and porous morphology. Under optimized conditions, the resulting calcium-based alginate-chitosan membrane achieved 40.5% Na<sup>+</sup> and 48.39% Cl<sup>-</sup> adsorptions, using 13.3 mL of 2% (w/v) chitosan and 26.6 mL of 2% (w/v) alginate with a 40-minutes contact time. The subsequent we applied for the desalination potential of calcium alginate, revealing the efficient reduction of NaCl levels in seawater. The calcium of coral skeletons collected was 90.86% and 93.41% before and after calcination, respectively, affirming the dominant calcium composition suitable for calcium alginate production. We identified an optimal 8-minute contact time for calcium alginate to effectively absorb NaCl, resulting in an 88.17% and 50% for Na<sup>+</sup> and Cl<sup>-</sup> absorptions. We applied the addition of chitosan into calcium-alginate membranes and its impact on enhancing salt adsorption efficiency for seawater desalination.</p> </abstract>

Metal-organic Skeleton (MOF) Composite based Using Electrochemical Immunobiosensor to Detect the Important Tumor Marker of Breast Cancer Glycotype Antigen 15-3

Breast cancer is one of the biggest threats to women's life and health in the world, and the mortality rate has reached the second highest in the world. With the development of metal organic skeleton (MOF) and the advantages of the composite in the field of electrochemistry and biosensing, various metal organic skeleton composites have been widely used in electrochemical biosensors. Thus, electrochemical biosensors have received extensive attention and research in the field of rapid breast cancer detection. This article mainly introduces the detection of sugar-type important tumor marker antigen 15-3, and electrochemical immunobiosensor Excellent performance in breast cancer detection and promising prospects for its application.

Anion elements incorporation into corals skeletons: Experimental approach for biomineralization and paleo-proxies.

The elemental composition of coral skeletons provides important information for palaeoceanographic reconstructions and coral biomineralization. Partition of anions and their stable isotopes in coral skeleton enables the reconstruction of past seawater carbonate chemistry, paleo-CO2, and past climates. Here, we investigated the partition of B, S, As, Br, I, and Mo into the skeletons of two corals, Acropora cervicornis and Pocillopora damicornis, as a function of calcium and carbonate concentrations.* Anion-to-calcium ratio in the corals (An/CaCoral) were correlated with the equivalent ratios in the culturing seawater (An/CO32-SW). Negative intercepts of these relationships suggest a higher CO32- concentration in the coral extracellular calcifying fluid (ECF) relative to seawater, from which the skeleton precipitates. The enrichment factor of CO32- at the ECF was 2.5 for A. cervicornis and 1.9 for P. damicornis, consistent with their relative calcification rates. The CO32-ECF concentrations thus calculated are similar to those proposed by previous studies based on B/Ca coupled with δ11B, as well as by direct measurements using microsensors and fluorescent dyes. Rayleigh fractionation modeling demonstrates a uniform Ca utilization at various CaSW concentrations, providing further evidence that coral calcification occurs directly from a semiclosed seawater reservoir as reported previously. The partition coefficients reported in this study for B, S, As, Br, I, and Mo open up wide possibilities for past ocean chemistry reconstructions based on Br having long residence time (~160 Ma) in the ocean. Other elements like S, Mo, B, as well as pCO2 may also be calculated based on these elements in fossil coral.

Study of bismuth metal organic skeleton composites with photocatalytic antibacterial activity

A composite based on Ag and carbon quantum dot (CQDs) doped bismuth metal organic framework (CAU-17) was synthesized by a one-step thermal solvent in situ growth. The microstructure, chemical composition, morphology, photogenerated electron-hole pairs, and photocatalytic activity of the composite were characterized. The produced composite with its unique energy band structure, enhances the visible light absorption and effectively delays the recombination of the photogenerated carriers. On the other hand, the modification with CQDs increases the concentration and transport rate of photogenerated carriers mainly attributed to their superior electron transport capacity and light trapping ability. The photocatalytic antibacterial effect of CAU-17/Ag/CQDs against common Gram-positive, Gram-negative bacteria (Staphylococcus aureus, Escherichia coli) and drug-resistant bacteria (methicillin-resistant Staphylococcus aureus), as well as its inhibition against HepG2 tumor cell were investigated. The results showed that CAU-17/Ag/CQDs exhibited a photocatalytic antibacterial effect with an inactivation rate as high as 99.9 %. At the low dose (0.2 mg/mL), CAU-17/Ag/CQDs indicated a significant inhibition against bacterial growth 20 min after visible light exposure, whereas at the concentration of 0.5 mg/mL, CAU-17/Ag/CQDs completely killed all the tested bacteria. At the concentration of 0.8 mg/mL, the inhibition rate against HepG2 tumor cells reached 75 %. The excellent photocatalytic property of the as prepared composite contributed to the doping of Ag and CQDs, which fundamentally altered the morphology and energy band distribution. Such a composite can be developed into an effective photocatalytic disinfection system and applied to water purification systems, biofilm rejection, combating different antibiotic resistances, and tumor therapy.

Correlation analysis of the gradation design parameters and mechanical performance of semi-flexible pavement

Semi-flexible pavement (SFP) has been widely used for ant-rutting performance and resistance in heavy load conditions. The asphalt mixture skeleton was the central part in the complex-skeleton material system. However, few studies have been made on the connection of asphalt mixture skeleton composition and performance on semi-flexible pavement material. Therefore, the relationship between the skeleton gradation volumetric characteristic and mechanical properties of semi-flexible pavement material was investigated. Eight gradations with different coarse aggregate contents were constituted. The mechanical performances were conducted to establish the relationship between primary gradation performance. The result shows that the porosity of the asphalt matrix and Cantabro abrasion test are related to the composition of gradation. The tensile performance, shear characteristics, and compressive strength were affected by the voids filled asphalt (VFA), porosity, and fine aggregate to asphalt ratio (FB), respectively. The Burgers model accurately reflected the creep curves of the semi-flexible pavement material specimens. The creep modulus was related to the VFA, porosity, and effective asphalt content (Pbe). The gradation design parameters of open-gradation asphalt mixtures for semi-flexible pavement materials could be obtained based on the target performance. It is possible to reduce material testing times based on the correlation analysis effectively.

Strategies to improve metal-organic frameworks and their derived oxides as lithium storage anode materials

Lithium-ion batteries (LIBs) are widely used as energy storage technology in emerging markets such as electric vehicles. The development of anode materials that can replace graphite materials is a hotspot of current research. Metal-organic frameworks (MOFs), as a kind of important porous inorganic organic hybrid crystals, have been developed and used as anode materials for LIBs. MOFs can be used as precursors for transition metal oxides (TMOs) with nanostructures based on unique properties such as their unique structure and morphological characteristic, and controllable skeleton composition. In this review, the application and recent progress of MOFs and their derived TMOs in anode materials for LIBs are reviewed. Attention is also paid to their electrochemical mechanisms and the mechanism of the cyclic capacity enhancement phenomenon. Finally, the challenges of MOFs and their derived TMOs as LIBs anode materials are discussed, and modification strategies to improve their electrochemical performance are analyzed and summarized.

Laser ablation mass spectrometry blast through detection in R.

Organisms that grow a hard carbonate shell or skeleton, such as foraminifera, corals or molluscs, incorporate trace elements into their shell during growth that reflect the environmental change and biological activity they experienced during life. These geochemical signals locked within the carbonate are archives used in proxy reconstructions to study past environments and climates, to decipher taxonomy of cryptic species and to resolve evolutionary responses to climatic changes. Here, we use laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as a time-resolved acquisition to quantify the elemental composition of carbonate shells and skeletons. We present the LABLASTER (Laser Ablation BLASt Through Endpoint in R) package, which imports a single time-resolved LA-ICP-MS analysis, then detects when the laser has ablated through the carbonate as a function of change in signal over time and outputs key summary statistics. We provide two examples within the package: a fossil planktic foraminifer and a tropical coral skeleton. We present the first R package that automates the selection of desired data during data reduction workflows. This is achieved by automating the detection of when the laser has ablated through a sample using a smoothed time series, followed by removal of off-target data points. The functions are flexible and adjust dynamically to maximise the duration of the desired geochemical target signal, making this package applicable to a wide range of heterogenous bioarchives. Visualisation tools for manual validation are also included. LABLASTER increases transparency and repeatability by algorithmically identifying when the laser has either ablated fully through a sample or across a mineral boundary and is thus no longer documenting a geochemical signal associated with the desired sample. LABLASTER's focus on better data targeting means more accurate extraction of biological and geochemical signals.

SiC@FeZnZiF as a Bifunctional Catalyst with Catalytic Activating PMS and Photoreducing Carbon Dioxide.

Herein, we encapsulated modified silicon carbide nanoparticles utilizing a metal-organic backbone. E-SiC-FeZnZIF composites were successfully prepared via Fe doping. The catalysis activity of this bifunctional composite material was evaluated by the degradation of tetracycline (THC) and carbamazepine (CBZ) and the reduction of carbon dioxide (CO2). Nano SiC has received widespread attention in advanced oxidation applications, especially in the catalytic activation of peroxymonosulfate (PMS). However, the inferior activity of SiC has severely restricted its practical use. In this study of dual functional composite materials, nano SiC was firstly etched under aqueous alkali. Then, zeolite imidazolate frame-8 (ZIF-8) was used for immobilization. The filling of the etched nano SiC with FeZnZiF was confirmed by SEM, XRD, FTIR, BET, and XPS analyses. In addition, E-SiC-FeZnZIF exhibited excellent catalytic activation of peroxymonosulfate (PMS) to oxidize water pollutants, which can degrade tetracycline hydrochloride (THC), achieving a removal rate of 72% within 60 min. Moreover, E-SiC-FeZnZIF exhibited a relatively high CO2 reduction rate with H2O. The yields of CO and CH4 were 0.085 and 0.509 μmol g-1, respectively, after 2 h, which are higher than that of 50 nm of commercial SiC (CO: 0.084 μmol g-1; CH4: 0.209 μmol g-1). This work provides a relatively convenient synthesis path for constructing metal skeleton composites for advanced oxidation and photocatalytic applications. This will have practical significance in protecting water bodies and reducing CO2, which are vital not only for maintaining the natural ecological balance and negative feedback regulation, but also for creating a new application carrier based on nano silicon carbide.

Modification of PVDF membrane by post-modified NH2-MIL-88B(Fe) showing improved permeability and oil/water separation performance

Metal organic frameworks (MOFs) possess excellent post-modification characteristics, high specific surface area, diversity of skeleton composition and pore tunability, have been increasingly applied in membrane modifications. In this work, NH2-MIL-88B(Fe) (NM88B) was first fixed onto polyvinylidene fluoride (PVDF) membrane by polyethyleneimine (PEI) through a vacuum-assisted self-assembly process, and the deposited NM88B was subsequently grafted with perfluoroalkyl polyethoxyacetic acid (FPEOAA) via a condensation reaction to realize the surface modifications. The modified membranes (named as N1Fx) showed improved hydrophilicity and underwater-oleophobicity. In addition, very high pure water flux (up to 9403 L‧m−2‧h−1) was obtained for the N1Fx membranes due to the high porosity of introduced NM88B. In the dead-end filtration experiments of n-hexadecane-water emulsion, the optimum membrane N1F20 showed a good oil rejection rate (98.3%) and high permeation flux (667 L‧m−2‧h−1) which is approximately seven times of the pure PVDF membrane, indicating that the surface-modified membranes had excellent permeability and good separation performance. Even after four filtration cycles of oil-water emulsion, the rejection rate maintained higher than 97%, showing good reusability. Furthermore, the study found that N1F20 had certain acid and alkaline resistance and great potential for engineering applications.

“Rigid-elastic chimera” pore skeleton model and overpressure porosity measurement method for shale: A case study of the deep overpressure siliceous shale of Silurian Longmaxi Formation in southern Sichuan Basin, SW China

Based on analysis of pore features and pore skeleton composition of shale, a “rigid elastic chimeric” pore skeleton model of shale gas reservoir was built. Pore deformation mechanisms leading to increase of shale porosity due to the pore skeleton deformation under overpressure were sorted out through analysis of stress on the shale pore and skeleton. After reviewing the difficulties and defects of existent porosity measurement methods, a dynamic deformed porosity measurement method was worked out and used to measure the porosity of overpressure Silurian Longmaxi Formation shale under real formation conditions in southern Sichuan Basin. The results show: (1) The shale reservoir is a mixture of inorganic rock particles and organic matter, which contains inorganic pores supported by rigid skeleton particles and organic pores supported by elastic-plastic particles, and thus has a special “rigid elastic chimeric” pore structure. (2) Under the action of formation overpressure, the inorganic pores have tiny changes that can be assumed that they don't change in porosity, while the organic pores may have large deformation due to skeleton compression, leading to the increase of radius, connectivity and ultimately porosity of these pores. (3) The “dynamic” deformation porosity measurement method combining high injection pressure helium porosity measurement and kerosene porosity measurement method under ultra-high variable pressure can accurately measure porosity of unconnected micro-pores under normal pressure conditions, and also the porosity increment caused by plastic skeleton compression deformation. (4) The pore deformation mechanism of shale may result in the “abnormal” phenomenon that the shale under formation conditions has higher porosity than that under normal pressure, so the overpressure shale reservoir is not necessarily “ultra-low in porosity”, and can have porosity over 10%. Application of this method in Well L210 in southern Sichuan has confirmed its practicality and reliability.

Influence of steel slag incorporation on internal skeletal contact characteristics within asphalt mixture

• Shape features of steel slag and limestone were calculated. • Meso-parameters of skeleton such as contact points and length were analyzed. • Gradations dominate the contact performance of steel slag in asphalt mixtures. • Potential interaction exists between gradation and slag content on skeleton contact. • Contact indicators of skeleton are remarkably influenced by aggregate angularity. This study employed X-ray computed tomography (CT) and image processing technology to characterize and quantify the internal skeleton composition within asphalt mixtures incorporating steel slag. The shape indices of steel slag and limestone including form and angularity features were calculated and meso-parameters of skeleton such as contact points, coordination number, and contact length were analysed, aiming to establish the relationship between aggregate shape and skeleton. The effect of gradations and slag contents were considered as well. Results denote gradations dominate the contact performance, the beneficial angularity of steel slag allows the promotion of contact originated by 4.75 mm-16.0 mm particles with surrounding ones in stone matrix asphalt (SMA-13), while encourages the contact from 2.36 mm to 4.75 mm particles in dense-graded asphalt concrete (AC-13). Instead of the common short contact lines in AC-13, the introduction of steel slag assures that SMA mixture creates plentiful longer contact lines among aggregates. Significance analysis indicates there is potential interaction between gradation and slag content on the skeleton contact. The skeleton of SMA mixture is more susceptible with slag content rather than AC one. Among overall meso-parameters, the average coordination number of 4.75 mm-9.5 mm particles and the sum of contact length are closely related to rut depth, and are remarkably influenced by the angularity of aggregate. These findings contribute to optimizing the skeleton design of steel slag asphalt mixture from the perspective of aggregate shape and possess enormous potential to reduce the dual environmental impacts of steel slag accumulation as well as resource mining.

Application of electrochemical biosensor based on metal organic framework materials in cancer detection

<p indent="0mm">In recent years, there has been an increasing study of metal-organic frameworks (MOFs) materials because of their many excellent properties, such as stable skeleton structure, adjustable pore scale, and large specific surface area, which make MOFs a substrate for fixing bioprobes for building electrochemical biosensors. The electrochemical biosensor is a detection device that combines the high specificity of tumor markers with the high sensitivity of electrochemical sensors through sensitive elements, which has a major application in clinical cancer screening. This article provides an overview of the classification of metal-organic skeleton composites, summarizing the various markers (such as cancer markers, microRNAs, and DNA) used over the past five years to detect and predict their development as indicators of early cancer diagnosis.

Mix design for pervious concrete based on the optimization of cement paste and granular skeleton to balance mechanical strength and permeability

• Mix design method for pervious concrete based on the optimization of cement paste and granular skeleton. • Validation using different w/b ratios, target porosities, and fine aggregate contents. • Measured air voids content for the designed mixtures met the corresponding target porosity, indicating the viability of the proposed method. • Designed mixtures achieved a compressive strength range of 11.9 to 28.3 MPa, tensile strength ≥2 MPa, and permeability coefficient ≥1 mm/s, meeting field application requirements for pedestrian and vehicle traffic. • Balanced mechanical strength, permeability, and resistance to degradation achieved especially in mixtures with 15% target porosity, w/b ratio 0.35, and 10% fine aggregate. The major concern for a broad field application of pervious is achieving mechanical performance and pore system efficiency to guarantee proper water infiltration. The inversely proportional relationship between mechanical strength and hydraulic conductivity demands mix-proportioning methods that equilibrate both requirements. This paper aims to fill this gap by proposing an easy-handling and flexible mix design method to optimize cement paste and granular skeleton composition to balance the mechanical strength and permeability of pervious concrete mixtures. The design concept was validated through an experimental program consisting of physical, mechanical, and hydraulic tests performed in designed pervious concrete mixtures considering three w/b ratios (0.30, 0.35, and 0.40), three target porosities (15%, 17.5%, and 20%), and three fine aggregate contents (0%, 10%, and 20%). Promising results were obtained in mixtures with 15% and 17.5% target porosity. The fine aggregate content influenced the permeability coefficient of the tested pervious concrete mixtures favorably. The fine aggregate content also influenced the compressive strength, especially in mixtures with 10% sand, which balanced the tested mechanical and hydraulic properties. The w/b ratio of 0.35 also resulted in pervious concrete mixtures with adequate functionality and balanced mechanical and permeability properties. The results validated the proposed mix design method that allowed a balance of physical, mechanical, and hydraulic properties to comply with requirements for field applications.

Impact energy absorption composites with shear stiffening gel-filled negative poisson's ratio skeleton by Kirigami method

A new type of Negative Poisson's ratio skeleton composites (NPRSC) filled with shear stiffening gels (SSG) is presented in this work. The skeleton is manufactured by Kirigami method for a simplest folding process. Combined with the shear stiffening property of SSG and auxetic effect of Negative Poisson's ratio (NPR) skeleton, the flexible composites show excellent impact energy absorption performance. Static compression experiment displays that compared with Positive Poisson's ratio (PPR) skeleton, the NPR structure composed of re-entrant elements is more flexible with a lower initial compression modulus for its special curvature effect. Dynamic impact experiments and numerical simulation reveals that the auxetic effect of NPR skeleton further facilitates the dynamic shear stiffening property of SSG and helps to dissipate the stress transversely. Specifically, the NPR skeleton contributes to a lower peak load, higher energy absorption ratio (EAR) and specific energy absorption (SEA) cooperated with SSG. The NPRSC exhibits improved energy absorption with the increase of impact velocity due to the strain rate sensitivity of SSG. This method provides an innovative idea for the structural design of shear stiffening materials and may be widely applied in the field of intelligent protection.

Polymorphism ofCaCO3and the variability of elemental composition of the calcareous skeletons secreted by invertebrates along the salinity gradient of the Baltic Sea

Biomineralization is of great importance in ecosystem functioning and for the use of carbonate skeleton as environmental proxies. Skeletal formation is controlled to different degrees by environmental parameters and biological mechanisms. While salinity is one of the most important factors affecting ecological processes and ocean physiochemistry, the goal of this investigation was to identify how salinity influences the mineral type and the concentrations of chemical elements in the whole skeleton of invertebrates from the Baltic Sea. In this model system, the surface salinity decreases from marine values (27.2) to almost fresh water (6.1). The selected organisms, mussels (Mytilus spp.), bryozoans (Einhornia crustulenta, Cribrilina cryptooecium, Cryptosula pallasiana, Electra pilosa, Escharella immersa), barnacles (Amphibalanus improvisus, Semibalanus balanoides), and polychaetes (Spirorbis tridentatus), precipitated skeleton composed of calcite and aragonite, most likely as a result of various interacting environmental and biological factors. The concentrations of all elements in bulk skeleton were highly variable between species from the same location, underlining the role of the biological mechanisms in skeletal formation. The concentration of Ca, Mg, Sr, and Na increased in the bulk skeleton of stenohaline organisms with increasing salinity, while in the bulk skeleton of euryhaline species, only the concentration of Na increased with increasing salinity. The concentrations of Mn, Ba, Cu, Pb, Y, V, Cd, and U in the skeleton of euryhaline species generally decreased at higher salinities, most likely reflecting the lower bioavailability of elements at higher salinity. However, the concentrations of elements in the skeleton of stenohaline organisms were highly variable with no clear salinity impact. This study suggests that, although the composition of skeleton of calcifying organisms along the salinity gradient of the Baltic Sea is to a large extent affected by biological mechanisms, it also reflects the responses to environmental conditions.

Distinct fine-scale variations in calcification control revealed by high-resolution 2D boron laser images in the cold-water coral Lophelia pertusa.

Coral calcification is a complex biologically controlled process of hard skeleton formation, and it is influenced by environmental conditions. The chemical composition of coral skeletons responds to calcification conditions and can be used to gain insights into both the control asserted by the organism and the environment. Boron and its isotopic composition have been of particular interest because of links to carbon chemistry and pH. In this study, we acquired high-resolution boron images (concentration and isotopes) in a skeleton sample of the azooxanthellate cold-water coral Lophelia pertusa. We observed high boron variability at a small spatial scale related to skeletal structure. This implies differences in calcification control during different stages of skeleton formation. Our data point to bicarbonate active transport as a critical pathway during early skeletal growth, and the variable activity rates explain the majority of the observed boron systematic.

Incorporation of Na and S in bamboo coral skeletons

Ocean environmental conditions can be inferred from the chemical composition of bamboo coral skeletons. The high magnesium calcite internodes of these long-living octocorals may therefore represent a potential archive for seawater properties such as salinity or temperature where instrumental time series are absent. To extend these time series into the past using a natural archive the principles of temperature and salinity signal incorporation into cold-water coral skeletal material need to be investigated. Since skeletal Na and S concentrations have been proposed as environmental proxies, we mapped the spatial distribution and concentration of these elements in two Atlantic specimens of Keratoisis grayi (family Isididae). These measurements were conducted with an electron microprobe applying a spatial resolution of 4 μm. The mean apparent distribution coefficient of Na/Ca for the two samples was within 2.5 and 2.8*10−4, while that of S shows a similar depletion relative to seawater with 3.8 and 3.6*10−3. The two elements show an inverse correlation in bamboo coral skeletons. The mean apparent distribution coefficient of Na is similar to that of abiotic calcites. This similarity can be interpreted as the absence of significant vital effects for skeletal Na/Ca. Hence it corroborates the idea that the average skeletal composition of bamboo corals holds the potential to record past seawater conditions. In contrast, it appears unlikely that the spatial variations of the element distribution of seemingly simultaneously precipitated material along growth rings are exclusively controlled by environmental factors. We further exclude Rayleigh fractionation, ion-specific pumping, and Ca/proton exchange as the driver of Na and S distribution in bamboo corals. Instead, we adapt a calcification model originally proposed for scleractinians to bamboo corals. This model can explain the observed distribution of Na and S in the skeleton by a combination of Ca/proton pumping, bicarbonate active transport, and the formation of an organic skeletal matrix. The adapted model can further be used to predict the theoretical behaviour of other elements and disentangle vital effects from external factors influencing compositional features. It is therefore a useful tool for future studies on the potential of bamboo corals as environmental archives.