Composition Of Skeletons Research Articles

Response of Acropora digitifera to ocean acidification: constraints from δ11B, Sr, Mg, and Ba compositions of aragonitic skeletons cultured under variable seawater pH

The response of Acropora digitifera to ocean acidification is determined using geochemical proxy measurements of the skeletal composition of A. digitifera cultured under a range of pH levels. We show that the chemical composition (δ11B, Sr/Ca, Mg/Ca, and Ba/Ca) of the coral skeletons can provide quantitative constraints on the effects of seawater pH on the pH in the calcification fluid (pHCF) and the mechanisms controlling the incorporation of trace elements into coral aragonite. With the decline of seawater pH, the skeletal δ11B value decreased, while the Sr/Ca ratio showed an increasing trend. The relationship between Mg/Ca and Ba/Ca versus seawater pH was not significant. Inter-colony variation of δ11B was insignificant, although inter-colony variation was observed for Ba/Ca. The decreasing trend of pHCF calculated from δ11B was from ~8.5, 8.4, and 8.3 for seawater pH of ~8.1, 7.8, and 7.4, respectively. Model calculations based on Sr/Ca and pHCF suggest that upregulation of pHCF occurs via exchange of H+ with Ca2+ with kinetic effects (Rayleigh fractionation), reducing Sr/Ca relative to inorganic deposition of aragonite from seawater. We show that it is possible to constrain the overall carbonate chemistry of the calcifying fluid with estimates of the carbonate saturation of the calcifying fluid (Ω CF) being derived from skeletal Sr/Ca and pHCF (from δ11B). These estimates suggest that the aragonite saturation state of the calcifying fluid Ω CF is elevated by a factor of 5–10 relative to ambient seawater under all treatment conditions.

Some Aspects Of Infiltration Of High Speed Steel Based Composites With Iron Addition

AbstractAttempts have been made to describe the influence of the production process parameters and additions of iron powders on properties of copper infiltrated HSS based composites. The powder compositions used to produce skeletons for further infiltration were: M3/2, M3/2+20% Fe and M3/2+50% Fe. The powders were cold pressed at 800 MPa. The infiltration process was carried out in vacuum. Both green compacts and preforms sintered for 60 minutes at 1150°C in vacuum were contact infiltrated with copper to yield final densities exceeding 97% of the theoretical value.The as-infiltrated composites were tested for Brinell hardness and bending strength, and subjected to wear tests performed by block-on-ring wear tester. From the analysis of the obtained results it has been found that the mechanical properties are mainly affected by the manufacturing route and composition of porous skeletons used for infiltration. Considerable differences in hardness between materials obtained from the two infiltration routes have been observed, with lower wear rates achieved after direct infiltration of green compacts.

(Invited) New Electrolyte Solvents and Additives Designed for Li Ion and Beyond Chemistries

Ever since the birth of Li ion chemistry, carbonate esters have been the main solvents used as the skeleton composition of the electrolytes. This class of polar organic compounds, ethylene carbonate in particular, brings both their merits of supporting reversible intercalation of Li+ at electrodes of potential differences as wide as 4.2 V, and their intrinsic limits of narrow temperature range, chemical reactivity toward conducting salts, and inflammability. Numerous efforts were made during the past decades in an attempt to replace these carbonate, either partially or entirely, but little change has occurred as the result. The emergence of new chemistries such as the high voltage (>4.5 V) cathode intercalation materials and the beyond-Li-ion concepts −− most of which resort to conversion-reaction concepts to maximize the specific capacities −− presents unprecedented challenges to these carbonate esters that have been widely used by Li-ion industry, and activities resumed in seeking new alternatives. This presentation will summarize our recent efforts of designing, synthesizing and characterizing such new electrolyte solvents in both high voltage and Li-ion as well as beyond-Li-ion chemistries.

Direct measurement of the boron isotope fractionation factor: Reducing the uncertainty in reconstructing ocean paleo-pH

The boron isotopic composition of calcium carbonate skeletons is a promising proxy method for reconstructing paleo-ocean pH and atmospheric CO2 from the geological record. Although the boron isotope methodology has been used extensively over the past two decades to determine ancient ocean-pH, the actual value of the boron isotope fractionation factor (εB) between the two main dissolved boron species, 11B(OH)3 and 10B(OH)−4, has remained uncertain. Initially, εB values were theoretically computed from vibrational frequencies of boron species, resulting in a value of ∼19‰. Later, spectrophotometric pH measurements on artificial seawater suggested a higher value of ∼27‰. A few independent theoretical models also pointed to a higher εB value. Here we provide, for the first time, an independent empirical fractionation factor (εB=26.0±1.0‰;25 °C), determined by direct measurements of B(OH)3 in seawater and other solutions. Boric acid was isolated by preferential passage through a reverse osmosis membrane under controlled pH conditions. We further demonstrate that applying the Pitzer ion-interaction approach, combined with ion-pairing calculations, results in a more accurate determination of species distribution in aquatic solutions of different chemical composition, relative to the traditional two-species boron-system approach. We show that using the revised approach reduces both the error in simulating ancient atmospheric CO2 (by up to 21%) and the overall uncertainty of applying boron isotopes for paleo-pH reconstruction. Combined, this revised methodology lays the foundation for a more accurate determination of ocean paleo-pH through time.

Marine sponges with contrasting life histories can be complementary biomonitors of heavy metal pollution in coastal ecosystems

In this study, we compared the usefulness of a long-living sponge (Hymeniacidon heliophila, Class Demospongiae) and a short-living one (Paraleucilla magna, Class Calcarea) as biomonitors of metallic pollution. The concentrations of 16 heavy metals were analyzed in both species along a gradient of decreasing pollution from the heavily polluted Guanabara Bay to the less impacted coastal islands in Rio de Janeiro, SE Brazil (SW Atlantic). The levels of most elements analyzed were higher in H. heliophila (Al, Co, Cr, Cu, Fe, Mn, Ni, Hg, Ni, and Sn) and P. magna (Ni, Cu, Mn, Al, Ti, Fe, Pb, Co, Cr, Zn, and V) collected from the heavily polluted bay when compared with the cleanest sites. Hymeniacidon heliophila accumulates 11 elements more efficiently than P. magna. This difference may be related to their skeleton composition, histological organization, symbiont bacteria and especially to their life cycle. Both species can be used as a biomonitors of metallic pollution, but while Hymeniacidon heliophila was more effective in concentrating most metals, Paraleucilla magna is more indicated to detect recent pollutant discharges due to its shorter life cycle. We suggest that the complementary use of species with contrasting life histories can be an effective monitoring strategy of heavy metals in coastal environments.

From the Arctic to the Antarctic: the major, minor, and trace elemental composition of echinoderm skeletons

AbstractBiogenic carbonate production in benthic marine ecosystems is dominated by representatives of the Echinodermata. Carbon and other major, minor, and trace elements are exported to the seabed where they accumulate or dissolve. Preserved carbonates (Mg‐calcite) have applications in oceanography and geochemistry and are used to reconstruct various parameters of ancient seawater, such as temperature (from Mg/Ca, Sr/Ca), seawater Mg/Ca (from Mg/Ca), and pH (from B/Ca). In general, the benthos is widely ignored for its role in the global carbon cycle despite the importance of echinoderms as a carbon sink (∼0.1–0.2 Pg C/yr). Echinoderms produce their skeletons from Mg‐calcite, which is more soluble than pure calcite and, therefore, more vulnerable to ocean acidification (OA). Minor and trace elements can also destabilize the calcite lattice, increasing the mineral's solubility. Little is known about the concentration of such elements in echinoderm tests. Expanding our knowledge on echinoderm skeleton composition will improve our understanding of elemental flux in the oceans. Furthermore, establishing relationships between the physical parameters of seawater and minor/trace elemental ratios within echinoderm Mg‐calcite should expand the utility of fossils as geochemical archives. Herein, we present elemental composition data for Asteroidea (n = 108; 9 families, 23 species), Echinoidea (n = 94; 8 families, 12 species), Ophiuroidea (n = 24; 4 families, 5 species), Holothuroidea (n = 7; 3 families, 3 species), and Crinoidea (n = 3; 1 family, 1 species), collected from the Arctic to the Antarctic oceans, from depths ranging from surface waters to 1200 m. The following elements were measured and normalized to [Ca]: Li, Be, Mg, Al, P, S, K, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Mo, Ag, Cd, Sn, Sb, Te, Ba, La, Ce, Nd, Dy, W, Re, Au, Hg, Tl, Pb, Bi, and U. Data are presented for the whole body, arms (plates), calcareous ossicles, spines, and test plates. Elements were quantified using inductively coupled plasma mass spectrometry. Our study presents the most comprehensive data set to date for a phylum whose skeletons are composed of Mg‐calcite.

δ13C and δ18O signatures from sea urchin skeleton: importance of diet type in metabolic contributions

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 476:153-166 (2013) - DOI: https://doi.org/10.3354/meps10159 δ13C and δ18O signatures from sea urchin skeleton: importance of diet type in metabolic contributions Patricia Prado1,2,*, Kenneth L. Heck Jr.3,4, Stephen A. Watts5, Just Cebrian3,4 1Institut de Recerca i Tecnología Agroalimentàries (IRTA), Aquatic Ecosystems, Ctra. Poble Nou km 5.5, 43540 Sant Carles de la Ràpita, Tarragona, Spain 2Department of Biology, East Carolina University, Greenville, North Carolina 27858, USA 3Dauphin Island Sea Laboratory, 101 Bienville Boulevard, Dauphin Island, Alabama 36528, USA 4Department of Marine Sciences, University of South Alabama, LSCB 25, Mobile, Alabama 36688, USA 5Department of Biology, University of Alabama at Birmingham, University Station, Birmingham, Alabama 35294-1170, USA *Email: patricia.prado@irta.cat ABSTRACT: The incorporation of δ13C and δ18O from respired CO2 to tests and whole calcified tissues (WCT) of the sea urchin Lytechinus variegatus was investigated in 120 individuals to elucidate the influence of diet type on the calcification process. Sea urchins were raised during 4 mo in controlled seawater tanks using 3 different diets (δ13C; δ18O) (means ± SE): seagrass (-10.2 ± 0.1‰; -15.2 ± 0.3‰), red macroalgae (-17.8 ± 1.4‰; -21.6 ± 0.8‰), and a formulated diet (-21.5 ± 0.04‰; -25 ± 0.4‰). Individuals fed the formulated and red macroalgae diets were depleted in both δ13C and δ18O compared to those fed seagrass. The isotope composition of skeletons mirrored that of organic carbon (δ13Co) and δ18O in diets, but contributions of dietary carbon were higher for urchins fed formulated (40.2 ± 1.2% in test and 34.8 ± 0.4% in WCT) or macroalgae diets (40.38 ± 1.1% in test and 32.1 ± 0.4% in WCT) than for those fed seagrass (29.1 ± 1% in test and 29.9 ± 0.7% in WCT), concurrently with greater growth rates and distinctive rates of fractionation. Differences between test and WCT contributions among diets could not be explained by patterns of biomass allocation across calcified structures (i.e. similar test to spines+lantern ratios for all diets). This suggests that individuals fed red macroalgae or formulated diets increased the amounts of dietary carbon going into their tests, whereas individuals fed seagrass did not. Overall, we identified diet type as a new factor in the process of carbonate deposition that could influence species’ responses to changes in ocean chemistry. We suggest that the reconstruction of sea urchin paleo-diets might also be possible from fossil records. Test structures may be particularly useful for this purpose, because they accumulate high contributions of metabolic carbon that enhance the detection of differences in the isotopic signatures of diets. KEY WORDS: Lytechinus variegatus · Metabolic CO2 · Biological calcification · Stable isotopes · Seagrass Full text in pdf format PreviousNextCite this article as: Prado P, Heck KL Jr, Watts SA, Cebrian J (2013) δ13C and δ18O signatures from sea urchin skeleton: importance of diet type in metabolic contributions. Mar Ecol Prog Ser 476:153-166. https://doi.org/10.3354/meps10159 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 476. Online publication date: February 27, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Constraining calcium isotope fractionation (δ44/40Ca) in modern and fossil scleractinian coral skeleton

The present study investigates the influence of environmental (temperature, salinity) and biological (growth rate, inter-generic variations) parameters on calcium isotope fractionation (δ44/40Ca) in scleractinian coral skeleton to better constrain this record. Previous studies focused on the δ44/40Ca record in different marine organisms to reconstruct seawater composition or temperature, but only few studies investigated corals.This study presents measurements performed on modern corals from natural environments (from the Maldives for modern and from Tahiti for fossil corals) as well as from laboratory cultures (Centre Scientifique de Monaco). Measurements on Porites sp., Acropora sp., Montipora verrucosa and Stylophora pistillata allow constraining inter-generic variability.Our results show that the fractionation of δ44/40Ca ranges from 0.6 to 0.1‰, independent of the genus or the environmental conditions. No significant relationship between the rate of calcification and δ44/40Ca was found. The weak temperature dependence reported in earlier studies is most probably not the only parameter that is responsible for the fractionation. Indeed, sub-seasonal temperature variations reconstructed by δ18O and Sr/Ca ratio using a multi-proxy approach, are not mirrored in the coral's δ44/40Ca variations. The intergeneric variability and intrageneric variability among the studied samples are weak except for S. pistillata, which shows calcium isotopic values increasing with salinity. The variability between samples cultured at a salinity of 40 is higher than those cultured at a salinity of 36 for this species.The present study reveals a strong biological control of the skeletal calcium isotope composition by the polyp and a weak influence of environmental factors, specifically temperature and salinity (except for S. pistillata). Vital effects have to be investigated in situ to better constrain their influence on the calcium isotopic signal. If vital effects could be extracted from the isotopic signal, the calcium isotopic composition of coral skeletons could provide reliable information on the calcium composition and budget in ocean.

The puzzling presence of calcite in skeletons of modern solitary corals from the Mediterranean Sea

The skeleton of scleractinian corals is commonly believed to be composed entirely of aragonite due to the current Mg/Ca molar ratio of seawater, which thermodynamically favours the deposition of this polymorph of calcium carbonate (CaCO3). However, some studies have shown that other forms of CaCO3 such as calcite can be present in significant amount (1–20%) inside tropical coral skeletons, significantly impacting paleo-reconstructions of SST or other environmental parameters based on geochemical proxies. This study aims at investigating for the first time, (1) the skeletal composition of two Mediterranean solitary corals, the azooxanthellate Leptopsammia pruvoti and the zooxanthellate Balanophyllia europaea, across their life cycle, (2) the distribution of the different CaCO3 forms inside skeletons, and (3) their implications in paleoclimatology. The origin of the different forms of CaCO3 observed inside studied coral skeletons and their relationships with the species’ habitat and ecological strategies are also discussed. CaCO3 composition of L. pruvoti and B. europaea was investigated at six sites located along the Italian coasts. Skeleton composition was studied by means of X-ray powder diffraction and Fourier transform infrared spectroscopy. A significant amount of calcite (1–23%) was found in more than 90% of the studied coral skeletons, in addition to aragonite. This calcite was preferentially located in the basal and intermediate areas than at the oral pole of coral skeletons. Calcite was also mainly located in the epitheca that covered the exposed parts of the coral in its aboral region. Interestingly in B. europaea, the calcite content was negatively correlated with skeleton size (age). The presence of calcite in scleractinian corals may result from different mechanisms: (1) corals may biologically precipitate calcite crystals at their early stages in order to insure their settlement on the substrate of fixation, especially in surgy environments; (2) calcite presence may result from skeletons of other calcifying organisms such as crustose coralline algae; and/or (3) calcite may result from the infilling of galleries of boring microorganisms which are known to colonize coral skeletons. We suggest that more than one of the above mentioned processes are involved.

Rayleigh-based, multi-element coral thermometry: A biomineralization approach to developing climate proxies

This study presents a new approach to coral thermometry that deconvolves the influence of water temperature on skeleton composition from that of “vital effects”, and has the potential to provide estimates of growth temperatures that are accurate to within a few tenths of a degree Celsius from both tropical and cold-water corals. Our results provide support for a physico-chemical model of coral biomineralization, and imply that Mg 2+ substitutes directly for Ca 2+ in biogenic aragonite. Recent studies have identified Rayleigh fractionation as an important influence on the elemental composition of coral skeletons. Daily, seasonal and interannual variations in the amount of aragonite precipitated by corals from each “batch” of calcifying fluid can explain why the temperature dependencies of elemental ratios in coral skeleton differ from those of abiogenic aragonites, and are highly variable among individual corals. On the basis of this new insight into the origin of “vital effects” in coral skeleton, we developed a Rayleigh-based, multi-element approach to coral thermometry. Temperature is resolved from the Rayleigh fractionation signal by combining information from multiple element ratios (e.g., Mg/Ca, Sr/Ca, Ba/Ca) to produce a mathematically over-constrained system of Rayleigh equations. Unlike conventional coral thermometers, this approach does not rely on an initial calibration of coral skeletal composition to an instrumental temperature record. Rather, considering coral skeletogenesis as a biologically mediated, physico-chemical process provides a means to extract temperature information from the skeleton composition using the Rayleigh equation and a set of experimentally determined partition coefficients. Because this approach is based on a quantitative understanding of the mechanism that produces the “vital effect” it should be possible to apply it both across scleractinian species and to corals growing in vastly different environments. Where instrumental temperature records are available, a Rayleigh-based framework allows the effects of stress on coral calcification to be identified on the basis of anomalies in the skeletal composition.

Effect of steel skeleton composition on the triboengineering properties of steel-copper pseudoalloys produced by infiltration

The effect of the composition of the skeleton made from steel powder on the triboengineering properties of pseudoalloys produced from copper alloy infiltration is analyzed. It is established that the steel-copper pseudoalloys possess a low friction coefficient depending on the concentration of graphite and additives of solid greases in the steel skeleton and on its original density. Higher copper phase concentration in the pseudoalloys boosts their heat conductivity and alters the structural morphology, thus promoting the triboengineering properties.

Growth rates, stable oxygen isotopes (δ18O), and strontium (Sr/Ca) composition in two species of Pacific sclerosponges (Acanthocheatetes wellsi and Astrosclera willeyana) with δ18O calibration and application to paleoceanography

The isotopic and elemental composition of sclerosponge skeletons is used to reconstruct paleoceanographic records. Yet few studies have systematically examined the natural variability in sclerosponge skeletal δ18O, growth, and Sr/Ca, and how that may influence the interpretation of sclerosponge proxy records. Here, we analyzed short records in seven specimens of Acanthocheatetes wellsi (high‐Mg calcite, 21 mol% Mg) from Palau, four A. wellsi (high‐Mg calcite, 21 mol% Mg) from Saipan, and three Astrosclera willeyana (aragonite) sclerosponges from Saipan, as well as one long record in an A. wellsi specimen from Palau spanning 1945–2001.5. In Saipan, species‐specific and mineralogical effects appear to have a negligible effect on sclerosponge δ18O, facilitating the direct comparison of δ18O records between species at a given location. At both sites, A. wellsi δ18O and growth rates were sensitive to environmental conditions, but Sr/Ca was not sensitive to the same conditions. High‐resolution δ18O analyses confirmed this finding as both A. wellsi and A. willeyana deposited their skeleton in accordance with the trends in isotopic equilibrium with seawater, though with a 0.27‰ offset in the case of A. willeyana. In the high‐Mg‐calcite species A. wellsi, Mg may be interfering with Sr incorporation into the skeleton. On multidecadal timescales, A. wellsi sclerosponge δ18O in Palau tracked the Southern Oscillation Index variability post‐1977, but not pre‐1977, coincident with the switch in the Pacific Decadal Oscillation (PDO) at ∼1976. This suggests that water mass circulation in the region is influenced by El Niño— Southern Oscillation variability during positive PDO phases, but not during negative ones.

LA-ICP-MS analyses on coral growth increments reveal heavy winter rain in the Eastern Mediterranean at 9 Ma

Sediment particles incorporated into coral skeletons reflect variation in composition and amount of suspended material in ambient water during coral growth. They can be used to identify periods of enhanced storm frequency and associated freshwater discharge. Tortonian (Late Miocene) Porites corals from Crete (Aegean Sea, Eastern Mediterranean) show pronounced annual density bands in X-ray photographs. δ 18O compositional variability reflects the annual banding equivalent with a ~ 7 °C annual sea surface temperature (SST) cycle over a seven-year period. Fine sediment particles are concentrated in layers with skeletal porosity parallel to growth increments. Variations in the chemical composition of coral skeletons can result from changes in the environment. Therefore, variations in element concentrations with a spatial resolution of ~ 500 µm along a transect perpendicular to growth increments were measured using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Complementary X-ray diffraction, X-ray fluorescence and scanning electron microscope analytical techniques were applied in order to characterize the sediment particles. Besides Sr/Ca and U/Ca variability indicating SST seasonality, the alternation of layers of pure aragonite and layers of aragonite coated with sediment particles (e.g., kaolinite, montmorillonite, quartz) is reflected in systematic variations in major and trace element concentrations. This element pattern results from a seasonal environmental mechanism where periodically enhanced input of sediment particles into the coral reef environment causes high concentrations of non-lattice bound elements (e.g., Al, Mn, Mg). Potential sources for the non-lattice bound elements (i.e., elements related to the clay minerals) such as airborne Saharan dust, Nile-derived sediment suspension as well as volcanic ash fall can be excluded on the basis of chemical, mineralogical or geological evidence. In contrast, normalized element patterns indicate that the clay minerals represent weathering products of local rocks, e.g., ophiolites, which at present crop out on Crete in mountainous areas, and formed islands exposed to erosion during the Late Miocene. High concentrations of the non-lattice bound elements correlate with low SSTs of the winter months. The discrepancy in SST estimations between δ 18O and Sr/Ca seasonality suggests that fresh water originating from intense winter rain caused a reduction of the annual δ 18O amplitudes and transported suspended material to the near-shore reef. Thus, we relate the seasonality in non-lattice bound element concentrations to climate variations in the Eastern Mediterranean region during the Late Miocene. Our results indicate that the present-day Mediterranean-type climate with a strong seasonality of precipitation and heavy winter rainfall events may have occurred at least temporarily during the Late Miocene at ~ 9 Ma in the Eastern Mediterranean.

Nanostructural Organization of Naturally Occurring Composites—Part II: Silica‐Chitin‐Based Biocomposites

Investigations of the micro‐ and nanostructures and chemical composition of the sponge skeletons as examples for natural structural biocomposites are of fundamental scientific relevance. Recently, we show that some demosponges (Verongula gigantea, Aplysina sp.) and glass sponges (Farrea occa, Euplectella aspergillum) possess chitin as a component of their skeletons. The main practical approach we used for chitin isolation was based on alkali treatment of corresponding external layers of spicules sponge material with the aim of obtaining alkali‐resistant compounds for detailed analysis. Here, we present a detailed study of the structural and physicochemical properties of spicules of the glass sponge Rossella fibulata. The structural similarity of chitin derived from this sponge to invertebrate alpha chitin has been confirmed by us unambiguously using physicochemical and biochemical methods. This is the first report of a silica‐chitin composite biomaterial found in Rossella species. Finally, the present work includes a discussion related to strategies for the practical application of silica‐chitin‐based composites as biomaterials.

Proteomic Analysis of a Membrane Skeleton Fraction from Human Liver

The cytoskeleton networks around liver cell cortex can resist Triton extraction and co-pellet with their tightly associated integral membrane proteins, forming assemblies called "membrane skeletons". Despite their important roles in determining cell shape and in signal transduction pathways, the membrane skeletons of human liver cells are uncharacterized to a great extent. In the present work, we prepared a membrane skeleton fraction by Triton extraction of human liver plasma membranes and then separated its protein components by 2-D gels. We optimized the detergent used for protein solubilization and found that 2% ASB-14 allowed the best recovery of membrane skeleton proteins. By analyzing the protein spots with MALDI-TOF and MALDI-TOF-TOF MS, we identified 104 nonredundant proteins, wherein 38 were cytoskeletal proteins that were further classified into several groups, including proteins in fodrin-based meshworks, adhesion proteins (proteins involved in adherens junctions, focal adhesions, desmosomes, hemidesmosomes and tight junctions), proteins that regulate F-actin dynamics, motor proteins, and some other cytoskeletal proteins. To the best of our knowledge, this is one of the largest data sets of membrane skeleton proteins to date. All the results suggested that the liver cells had complex actin- and cytokeratin-based membrane skeletons. This work provided a representative 2-DE map of membrane skeletons from human normal liver, for the purpose of helping to elucidate the composition and function of the membrane skeletons.

A centuries old problem in nephtheid taxonomy approached using DNA data (Coelenterata: Alcyonacea)

The current centuries old classification of the family Nephtheidae is still mostly based on colony morphology. In this family the Indo-Pacifc genera Litophyton, Nephthea, Dendronephthya and Stereonephthya, and the Atlantic genus Neospongodes form a complex mix of closely related, poorly described species which cannot be recognized using only colony morphology. Attempts with the more modern approach of comparing skeleton composition (sclerites) have been only partly successful because of the extreme variation of sclerite forms present in these genera. The genus Chromonephthea Van Ofwegen, 2005, introduced for several species previously assigned to Dendronephthya, Nephthea and Stereonephthya, was established with sclerite morphology, but the true generic status of the majority of the nominal species of these genera remained unresolved. In an attempt to clarify the phylogenetic relationships between Litophyton, Nephthea, Stereonephthya and Chromonephthea fourteen specimens, unidentified but certainly belonging to these genera, have been used in molecular analyses. All analyses supported two clades, which could be related to the shape of the sclerites present in the polyp stalks. One clade contained the specimens with characters for Stereonephthya along with the Chromonephthea specimen as a sister group. The other clade had a ‘true’ Nephthea and Litophyton together with the specimens that could not be placed in any particular genus using the old classification criteria. The consequences of these results for nephtheid classification are discussed.

Deep-sea coral geochemistry: Implication for the vital effect

Deep-sea corals hold a great potential as a key to important aspects of paleoceanography for at least two reasons, 1) they offer temporal high resolution records of deep-sea environment, because they have growth banding structures, 2) and they are well suited for studying vital effects, because the deep-sea environment does not change over short time scales. However, the relationship between the chemical composition of deep-sea coral skeletons and environmental factors is not well understood. In this study, the chemical composition of deep-sea corals was measured in bulk individuals and along skeletal micro-structures. Among the bulk individuals, δ 18O value and Sr / Ca ratio show a negative but weak correlation with ambient temperature. On the other hand, the Mg / Ca ratio has a positive, weak correlation with the temperature. Large variations were found among samples collected from similar temperature. The variation is up to 3.8‰ for δ 18O, 0.9 mmol/mol for Sr / Ca ratios, and 0.78 mmol/mol for Mg / Ca ratios among samples with ambient average temperature within 1 °C. This variation may be due to a large vital effect. The centers of calcification (COCs), which were formed at high calcification rate, have lower Sr / Ca, U / Ca and higher Mg / Ca ratios than surrounding fasciculi. This chemical distribution supports the model that elemental incorporation depends on calcification rate. This suggests that calcification rate is a very important factor for the chemical composition in deep-sea corals and is one of the most significant mechanisms of the vital effect. Because of this large vital effect, further investigations are essential to use the deep-sea coral as a temperature proxy.

Correlated trace element “vital effects” in tropical corals: A new geochemical tool for probing biomineralization

Micron-scale variations in the trace-element (TE) composition of tropical coral skeletons were measured using laser-ablation ICP-MS (LA-ICP-MS) as part of an investigation into the chemical processes underlying paleoenvrionmental proxy reconstructions. Fluctuations in B, Mg, Sr, Ba and U were measured at high spatial resolution in two Porites corals from the Great Barrier Reef (Australia), and the fine-scale fluctuations (< ∼1.0 mm) were compared with seasonal TE cycles in a third coral. Fine-scale TE variations were found to have a large amplitude over distances corresponding to less than 1 month growth. Variations were quasi-periodic and appeared to have characteristic wavelengths on weekly (6–7 d) and monthly (28 d) scales, although periodicity was not continuous and variations could not be matched either within or between individual corallites. Fine-scale variations between Mg, Sr and U were significantly correlated with each other (Sr and U are positively correlated, but negatively correlated with Mg). This 3D correlation “vector” has the same slope as the seasonal-scale Mg, Sr and U correlations, suggesting that the same chemical/biologic biomineralization process mediates trace element variations at both timescales. Importantly, the fine-scale variations are too large to be caused directly by daily to monthly fluctuations in sea-surface temperature. This means that seasonal variations in these elements cannot reflect purely inorganic temperature-dependent coprecipitation. Models of physicochemical calcification were developed to test whether changes in calcification rate could explain the trace-element correlations. The calculations show that increases in calcification rate will result in correlated decreases in all TE/Ca ratios. The models reproduce the Sr partition coefficient, trace-element correlation slopes, and amplitude of fine-scale variations for an average calcifying pH of 8.5, varying by ±0.2 pH units. The models, however, predict U partition coefficients which are too low, and cannot reproduce the negative correlation between Mg and the other trace elements, which may be caused by crystallographic factors.

Impact of environmental seasonality on stable isotope composition of skeletons of the temperate bryozoan Cellaria sinuosa

Stable oxygen and carbon isotopes of skeletons of the anascan bryozoan Cellaria sinuosa (Hassall) from waters off Roscoff (outer British Channel) were studied to obtain information on seasonal changes of the environments monitored in the skeleton of the bryozoan. The isotope signals found in the skeletons cover a time span of three years (1993–1995). δ 18O c is incorporated into the skeleton close to isotopic equilibrium, whereas δ 13C is characterised by distinctly lower values relative to the predicted equilibrium indicating a strong component of respiratory CO 2 incorporated into the bryozoan skeleton. δ 18O c values document the annual cycle of temperature while δ 13C shows no clear seasonal cyclicity of primary productivity. The lack of correlation between δ 18O c and δ 13C values in individual profiles, however, monitors the offset between seasonal temperature and phytoplankton cycles. Correspondence of δ 13C values with the bryozoan life cycle indicates reduced metabolism during reproduction and refers toward a switch of used carbon reservoirs from respiratory CO 2 to DIC pool. Cellaria sinuosa shows an age of 1.5 years with an annual growth rate of approximately 32 mm/yr. Carbonate production by C. sinuosa on the shelf off Roscoff varies between 12 gr/m 2/yr and 57 gr/m 2/yr and lies within the range of cold-water carbonates.

Chitin characterization by SEM, FTIR, XRD, and 13C cross polarization/mass angle spinning NMR

AbstractThe full characterization of chitin obtained from squid, shrimp, prawn, lobsters, and king crab is reported. Elemental analysis, including metals such as Ca, Mg, Zn, Cd, Hg, Cr, Mn, Cu, and Pb, was performed, which is quite relevant because the skeleton composition is slightly different for each species. The morphology was studied by means of TEM and their compositions were determined by energy‐dispersive X‐ray analysis. 13C cross polarization/magic angle spinning NMR was applied to determine the chemical shift of all the carbons and the difference between them. Chitin was isolated by using chemical methods, alternating hydrochloric acid and sodium hydroxide. The α‐chitin from shrimp, prawn, lobsters, and king crabs showed two signals at 73.7 and 75.6 ppm. Meanwhile, the β‐chitin from squid exhibited one signal at 75.2 ppm. FTIR studies were used to analyze α‐chitin from shrimp and β‐chitin from squid. The α‐chitin exhibited amide I vibration modes at 1660 and 1627 cm−1, whereas the β‐chitin showed one band at 1656 cm−1. X‐ray diffraction showed that α‐chitin is orthorhombic (a = 4.74 Å, b = 18.86 Å, and c = 10.32 Å) and β‐chitin had a monoclinic dihydrated form (a = 4.80 Å, b = 10.40 Å, c = 11.10 Å, and β = 97°). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1876–1885, 2004